Ficus aurea

Ficus aurea, commonly known as the Florida strangler fig (or simply strangler fig), golden fig, or higuerón, is a tree in the family Moraceae that is native to the U.S. state of Florida, the northern and western Caribbean, southern Mexico and Central America south to Panama. The specific epithet aurea was applied by English botanist Thomas Nuttall who described the species in 1846.

Ficus aurea is a strangler fig. In figs of this group, seed germination usually takes place in the canopy of a host tree with the seedling living as an epiphyte until its roots establish contact with the ground. After that, it enlarges and strangles its host, eventually becoming a free-standing tree in its own right. Individuals may reach 30 m (100 ft) in height. Like all figs, it has an obligate mutualism with fig wasps: figs are only pollinated by fig wasps, and fig wasps can only reproduce in fig flowers. The tree provides habitat, food and shelter for a host of tropical lifeforms including epiphytes in cloud forests and birds, mammals, reptiles and invertebrates. F. aurea is used in traditional medicine, for live fencing, as an ornamental and as a bonsai.

## Description

Ficus aurea is a tree which may reach heights of 30 m (98 ft). It is monoecious: each tree bears functional male and female flowers. The size and shape of the leaves is variable. Some plants have leaves that are usually less than 10 cm (4 in) long while others have leaves that are larger. The shape of the leaves and of the leaf base also varies—some plants have leaves that are oblong or elliptic with a wedge-shaped to rounded base, while others have heart-shaped or ovate leaves with cordate to rounded bases. F. aurea has paired figs which are green when unripe, turning yellow as they ripen. They differ in size (0.6–0.8 cm [0.2–0.3 in], about 1 cm [0.4 in], or 1.0–1.2 cm [0.4–0.5 in] in diameter); figs are generally sessile, but in parts of northern Mesoamerica figs are borne on short stalks known as peduncles.

## Taxonomy

With about 750 species, Ficus (Moraceae) is one of the largest angiosperm genera (David Frodin of Chelsea Physic Garden ranked it as the 31st largest genus). Ficus aurea is classified in the subgenus Urostigma (the strangler figs) and the section Americana. Recent molecular phylogenies have shown that subgenus Urostigma is polyphyletic, but have strongly supported the validity of section Americana as a discrete group (although its exact relationship to section Galoglychia is unclear).

Thomas Nuttall described the species in the second volume of his 1846 work The North American Sylva with specific epithet aurea ('golden' in Latin). In 1768, Scottish botanist Philip Miller described Ficus maxima, citing Carl Linnaeus' Hortus Cliffortianus (1738) and Hans Sloane's Catalogus plantarum quæ in insula Jamaica (1696). Sloane's illustration of the species, published in 1725, depicted it with figs borne singly, a characteristic of the Ficus subgenus Pharmacosycea. As a member of the subgenus Urostigma, F. aurea has paired figs. However, a closer examination of Sloane's description led Cornelis Berg to conclude that the illustration depicted a member of the subgenus Urostigma (since it had other diagnostic of that subgenus), almost certainly F. aurea, and that the illustration of singly borne figs was probably artistic license. Berg located the plant collection upon which Sloane's illustration was based and concluded that Miller's F. maxima was, in fact, F. aurea. In his description of F. aurea, which was based on plant material collected in Florida, Thomas Nuttall considered the possibility that his plants belonged to the species that Sloane had described, but came to the conclusion that it was a new species. Under the rules of botanical nomenclature, the name F. maxima has priority over F. aurea since Miller's description was published in 1768, while Nuttall's description was published in 1846.

In their 1914 Flora of Jamaica, William Fawcett and Alfred Barton Rendle linked Sloane's illustration to the tree species that was then known as Ficus suffocans, a name that had been assigned to it in August Grisebach's Flora of the British West Indian Islands. Gordon DeWolf agreed with their conclusion and used the name F. maxima for that species in the 1960 Flora of Panama. Since this use has become widespread, Berg proposed that the name Ficus maxima be conserved in the way DeWolf had used it, a proposal that was accepted by the nomenclatural committee.

Reassigning the name Ficus maxima did not leave F. aurea as the oldest name for this species, as German naturalist Johann Heinrich Friedrich Link had described Ficus ciliolosa in 1822. Berg concluded that the species Link described was actually F. aurea, and since Link's description predated Nuttall's by 24 years, priority should have been given to the name F. ciliolosa. Since the former name was widely used and the name F. ciliolosa had not been, Berg proposed that the name F. aurea be conserved. In response to this, the nomenclatural committee ruled that rather than conserving F. aurea, that it would be better to reject F. ciliolosa. Conserving F. aurea would mean that precedence would be given to that name over all others. By simply rejecting F. ciliolosa, the committee left open the possibility that the name F. aurea could be supplanted by another older name, if one were to be discovered.

### Synonyms

In 1920, American botanist Paul C. Standley described three new species based on collections from Panama and Costa Rica—Ficus tuerckheimii, F. isophlebia and F. jimenezii. DeWolf concluded that they were all the same species, and Berg synonymised them with F. aurea. These names have been used widely for Mexican and Central American populations, and continue to be used by some authors. Berg suspected that Ficus rzedowskiana Carvajal and Cuevas-Figueroa may also belong to this species, but he had not examined the original material upon which this species was based.

Berg considered F. aurea to be a species with at least four morphs. "None of the morphs", he wrote, "can be related to certain habitats or altitudes." Thirty years earlier, William Burger had come to a very different conclusion with respect to Ficus tuerckheimii, F. isophlebia and F. jimenezii—he rejected DeWolf's synonymisation of these three species as based on incomplete evidence. Burger noted that the three taxa occupied different habitats which could be separated in terms of rainfall and elevation.

## Reproduction and growth

Figs have an obligate mutualism with fig wasps, (Agaonidae); figs are only pollinated by these wasps, and they can only reproduce in fig flowers. Generally, each fig species depends on a single species of wasp for pollination. The wasps are similarly dependent on their fig species in order to reproduce. Ficus aurea is pollinated by Pegoscapus mexicanus (Ashmead).

Figs have complicated inflorescences called syconia. Flowers are entirely contained within an enclosed structure. Their only connection with the outside is through a small pore called ostiole. Monoecious figs like F. aurea have both male and female flowers within the syconium. Female flowers mature first. Once mature, they produce a volatile chemical attractant. Female wasps squeeze their way through the ostiole into the interior of the syconium. Inside the syconium, they pollinate the flowers, lay their eggs in some of them, and die. The eggs hatch and the larvae parasitise the flowers in which they were laid. After four to seven weeks (in F. aurea), adult wasps emerge. Males emerge first, mate with the females, and cut exit holes through the walls of the fig. The male flowers mature around the same time as the female wasps emerge. The newly emerged female wasps actively pack their bodies with pollen from the male flowers before leaving through the exit holes the males have cut and fly off to find a syconium in which to lay their eggs. Over the next one to five days, figs ripen. The ripe figs are eaten by various mammals and birds which disperse the seeds.

### Phenology

Figs flower and fruit asynchronously. Flowering and fruiting is staggered throughout the population. This fact is important for fig wasps—female wasps need to find a syconium in which to lay their eggs within a few days of emergence, something that would not be possible if all the trees in a population flowered and fruited at the same time. This also makes figs important food resources for frugivores (animals that feed nearly exclusively on fruit); figs are one of the few fruit available at times of the year when fruit are scarce.

Although figs flower asynchronously as a population, in most species flowering is synchronised within an individual. Newly emerged female wasps must move away from their natal tree in order to find figs in which to lay their eggs. This is to the advantage of the fig, since it prevents self-pollination. In Florida, individual F. aurea trees flower and fruit asynchronously. Within-tree asynchrony in flowering is likely to raise the probability of self-pollination, but it may be an adaptation that allows the species to maintain an adequate population of wasps at low population densities or in strongly seasonal climates.

Flowering phenology in Ficus has been characterised into five phases. In most figs, phase A is followed almost immediately by phase B. However, in F. aurea immature inflorescences can remain dormant for more than nine months.

### Growth

Ficus aurea is a fast-growing tree. As a hemiepiphyte it germinates in the canopy of a host tree and begins life as an epiphyte before growing roots down to the ground. F. aurea is also a strangler fig (not all hemiepiphytic figs are stranglers)—the roots fuse and encircle the host tree. This usually results in the death of the host, since it effectively girdles the tree. Palms, which lack secondary growth, are not affected by this, but they can still be harmed by competition for light, water and nutrients. Following Hurricane Andrew in 1992, F. aurea trees regenerated from root suckers and standing trees.

## Distribution

Ficus aurea ranges from Florida, across the northern Caribbean to Mexico, and south across Central America. It is present in central and southern Florida and the Florida Keys, The Bahamas, the Caicos Islands, Hispaniola, Cuba, Jamaica, the Cayman Islands, San Andrés (a Colombian possession in the western Caribbean), southern Mexico, Belize, Guatemala, Honduras, Nicaragua, El Salvador, Costa Rica and Panama. It grows from sea level up to 1,800 m (5,500 ft) above sea level, in habitats ranging from Bahamian dry forests, to cloud forest in Costa Rica.

Ficus aurea is found in central and southern Florida as far north as Volusia County; it is one of only two native fig species in Florida. The species is present in a range of south Florida ecosystems, including coastal hardwood hammocks, cabbage palm hammocks, tropical hardwood hammocks and shrublands, temperate hardwood hammocks and shrublands and along watercourses. In The Bahamas, F. aurea is found in tropical dry forests on North Andros, Great Exuma and Bimini. F. aurea occurs in 10 states in Mexico, primarily in the south, but extending as far north as Jalisco. It is found in tropical deciduous forest, tropical semi-evergreen forest, tropical evergreen forest, cloud forest and in aquatic or subaquatic habitats.

## Ecology

Ficus aurea is a strangler fig—it tends to establish on a host tree which it gradually encircles and "strangles", eventually taking the place of that tree in the forest canopy. While this makes F. aurea an agent in the mortality of other trees, there is little to indicate that its choice of hosts is species specific. However, in dry forests on Great Exuma in The Bahamas, F. aurea establishes exclusively on palms, in spite of the presence of several other large trees that should provide suitable hosts. Eric Swagel and colleagues attributed this to the fact that humus accumulates on the leaf bases of these palms and provides a relatively moist microclimate in a dry environment, facilitating seedling survival.

Figs are sometimes considered to be potential keystone species in communities of fruit-eating animals because of their asynchronous fruiting patterns. Nathaniel Wheelwright reports that emerald toucanets fed on unripe F. aurea fruit at times of fruit scarcity in Monteverde, Costa Rica. Wheelwright listed the species as a year-round food source for the resplendent quetzal at the same site. In the Florida Keys, F. aurea is one of five fruit species that dominate the diet fed by white-crowned pigeons to their nestlings. F. aurea is also important in the diet of mammalian frugivores—both fruit and young leaves are consumed by black howler monkeys in Belize.

The interaction between figs and fig wasps is especially well-known (see section on reproduction, above). In addition to its pollinators (Pegoscapus mexicanus), F. aurea is exploited by a group of non-pollinating chalcidoid wasps whose larvae develop in its figs. These include gallers, inquilines and kleptoparasites as well as parasitoids of both the pollinating and non-pollinating wasps.

The invertebrates within F. aurea syconia in southern Florida include a pollinating wasp, P. mexicanus, up to eight or more species of non-pollinating wasps, a plant-parasitic nematode transported by the pollinator, mites, and a predatory rove beetle whose adults and larvae eat fig wasps. Nematodes: Schistonchus aureus (Aphelenchoididae) is a plant-parasitic nematode associated with the pollinator Pegoscapus mexicanus and syconia of F. aurea. Mites: belonging to the family Tarsonemidae (Acarina) have been recognized in the syconia of F. aurea and F. citrifolia, but they have not been identified even to genus, and their behavior is undescribed. Rove beetles: Charoxus spinifer is a rove beetle (Coleoptera: Staphylinidae) whose adults enter late-stage syconia of F. aurea and F. citrifolia. Adults eat fig wasps; larvae develop within the syconia and prey on fig wasps, then pupate in the ground.

As a large tree, F. aurea can be an important host for epiphytes. In Costa Rican cloud forests, where F. aurea is "the most conspicuous component" of intact forest, trees in forest patches supported richer communities of epiphytic bryophytes, while isolated trees supported greater lichen cover.

Florida International University ecologist Suzanne Koptur reported the presence of extrafloral nectaries on F. aurea figs in the Florida Everglades. Extrafloral nectaries are structures which produce nectar but are not associated with flowers. They are usually interpreted as defensive structure and are often produced in response to attack by insect herbivores. They attract insects, primarily ants, which defend the nectaries, thus protecting the plant against herbivores.

## Uses

Ficus aurea, amongst other related Ficus species, has been a source of bark for preparing amate, the bark paper used for codices in the Mesoamerican civilizations. The oldest example dates back to 75 CE and was found in a shaft tomb culture site in Huitzilapa, Jalisco in Mexico.

The fruit of Ficus aurea is edible and was used for food by the Native Americans and early settlers in Florida; it is still eaten occasionally as a backyard source of native fruit. The latex was used to make a chewing gum, and aerial roots may have been used to make lashings, arrows, bowstrings and fishing lines. The fruit was used to make a rose-coloured dye. F. aurea was also used in traditional medicine in The Bahamas and Florida. Allison Adonizio and colleagues screened F. aurea for anti-quorum sensing activity (as a possible means of anti-bacterial action), but found no such activity.

Individual F. aurea trees are common on dairy farms in La Cruz, Cañitas and Santa Elena in Costa Rica, since they are often spared when forest is converted to pasture. In interviews, farmers identified the species as useful for fence posts, live fencing and firewood, and as a food species for wild birds and mammals.

Ficus aurea is used as an ornamental tree, an indoor tree and as a bonsai. Like other figs, it tends to invade built structures and foundations, and needs to be removed to prevent structural damage. Although young trees are described as "rather ornamental", older trees are considered to be difficult to maintain (because of the adventitious roots that develop off branches) and are not recommended for small areas. However, it was considered a useful tree for "enviroscaping" to conserve energy in south Florida, since it is "not as aggressive as many exotic fig species," although it must be given enough space.

Species of strangler fig

Flora without expected TNC conservation status


Dangerous (Michael Jackson album)

Dangerous is the eighth studio album by the American singer-songwriter Michael Jackson. It was released by Epic Records on November 26, 1991, more than four years after Jackson's previous album, Bad (1987). Co-produced by Jackson, Bill Bottrell, Teddy Riley, and Bruce Swedien, the album was Jackson's first since Forever, Michael (1975) without longtime collaborator Quincy Jones. Guest appearances include Heavy D, Princess Stéphanie of Monaco, Slash and Wreckx-n-Effect. The album incorporates R&B, pop and new jack swing, a growing genre at the time. Elements of industrial, funk, hip hop, electronic, gospel, classical and rock are also present. Twelve of the album's fourteen songs were written or co-written by Jackson, discussing topics like racism, poverty, romance, self-improvement, and the welfare of children and the world.

Dangerous is considered an artistic change for Jackson, with his music focusing on more socially conscious material, and including a broader range of sounds and styles. It features catchy pop hooks and choruses while also introducing underground sounds to a mainstream audience. The album's tone is noted by critics as gritty and urban, with sounds including synthetic basslines, scratching, and drum machine percussion, as well as unconventional sounds like honking vehicle horns, sliding chains, swinging gates, breaking glass, and clanking metal. Jackson also incorporates beatboxing, scat singing, and finger snapping throughout the album.

Dangerous debuted at number one on the US Billboard Top Pop Albums chart and in thirteen other countries, selling 5 million copies worldwide in its first week and went on to be the best-selling album worldwide of 1992. Nine singles premiered between November 1991 and December 1993, including one exclusively released outside North America ("Give In to Me"). The album produced four singles that reached the top ten of the US Billboard Hot 100: "Remember the Time", "In the Closet", "Will You Be There" and the number-one single "Black or White". The Dangerous World Tour grossed \$100 million (equivalent to \$177 million in 2019), making it one of the highest-grossing tours of the 1990s.

Dangerous is one of the best-selling albums of all time, having sold over 32 million copies worldwide, and was certified 8× Platinum by the Recording Industry Association of America (RIAA) in August 2018. Dangerous received worldwide praise, and it influenced contemporary pop and R&B artists. It has been included in several publications' lists of the greatest albums of all time. At the 1993 Grammy Awards, it received four Grammy Award nominations, winning Best Engineered Album, Non-Classical, while Jackson was awarded the Grammy Legend Award. Jackson won three American Music Awards at the 1993 American Music Awards, including the inaugural International Artist Award. Jackson also received Billboard Music Awards for Best Worldwide Album and Best Worldwide Single for "Black or White".

## Background

After the success of his seventh album, Bad (1987), Jackson wanted more independence and control over the creative process. He separated himself from longtime producer Quincy Jones to avoid the perception that his success depended on him. Jackson began working on new tracks in 1989 with a handful of members from the B-team of Bad, including Matt Forger and Bill Bottrell. The album was conceived as a greatest-hits collection, Decade, with a handful of new songs, similar to Madonna's The Immaculate Collection. Jackson signed off on the idea in early 1989 and test pressings were made by Epic Records. Jackson received \$18 million in advance.

Decade was scheduled for a late 1989 release but was delayed several times. Another release date was set for November 1990, but it never materialized. Jackson was preoccupied with ongoing changes in his management team while also attempting to realize his film-making ambitions. In June 1990, he collapsed while dancing in his home studio due to a possible panic attack, with symptoms of chest pains, dehydration and inflammation of the ribs. Soon after, Decade was dropped entirely, and Jackson determined that his new material constituted a full album, which he called Dangerous.

## Recording

For nearly two years starting in late 1989, recording took place primarily at Ocean Way Record One in Sherman Oaks, where Jackson arranged for executive control for \$4,000 per day. Most work proceeded with three producers, Bill Bottrell, Bruce Swedien, and Bryan Loren, in three different studios with Jackson. Bottrell co-wrote and produced "Give In to Me" and "Black or White", and received writing credits for "Dangerous" and production credits for "Who Is It". He had been forced out of the production of Bad by Jones, but Jackson brought him back for Dangerous, for which he was known as the "rock guy". Bottrell introduced Jackson to classically trained keyboardist Brad Buxer, who was originally hired as a technician for his expertise in electronic equipment. Buxer recalled: "Musically speaking, we were on the same wavelength; we spoke the same language." The Jackson-Buxer partnership continued for 20 years.

For most of the rhythm tracks, Jackson worked with Loren at Westlake Studios. Their work had begun at the end of Jackson's Bad tour, and together they recorded "Work That Body", "She Got It", "Serious Effect", "Do Not Believe It", "Seven Digits", and "Man in Black". Loren wanted to recapture the organic R&B feeling of Jackson's albums Off the Wall and Thriller. LL Cool J was invited to rap on "Serious Effect" and "Truth About Youth", because Jackson wanted to add hip-hop to the record. LL Cool J had been critical of Jackson but praised him after their collaboration. None of Loren's recordings made the album. Though Loren's material was strong, it was not up to Jackson's standards, and he was searching for a sound as compelling and successful as Rhythm Nation (1989) by his sister Janet Jackson.

Jackson discovered new jack swing, featuring a more aggressive and urban sound, after reaching out to producers Antonio "L.A." Reid and Kenny "Babyface" Edmonds. In June 1990, Jackson hired Teddy Riley, pioneer of the new jack swing genre. By then, Jackson had already recorded over 50 songs. Initially recording at Record One, Riley moved to nearby Larrabee Studios after a few weeks, because other producers were working at Sherman Oaks. Unlike Loren, Riley wanted Dangerous to sound different from Jackson's earlier work, and Jackson admired Riley for bringing in contemporary styles. Jackson challenged Riley to create new instrumentation without relying on stock synth and drum machine sounds. Riley reworked some of Loren's contributions, including "She Got It" and "Serious Effect", and developed "Jam" and "Dangerous" further. "Dangerous" was originally recorded with Bottrell, but Jackson was not satisfied until improvements were made. Riley said he brought Jackson's music back to its "barest forms" of R&B and funk.

By early 1991 Jackson had finished the track list, which included several tracks he recorded with Riley: "Remember the Time", "Dangerous", and "In the Closet". He had planned for "In the Closet" to be a duet with pop singer Madonna, but her half was replaced with Princess Stéphanie of Monaco. A meeting with guitarist Slash took more than a year to co-ordinate, and the two collaborated on "Give In to Me". Swedien recalled recording sessions lasting up to 18 hours. On one occasion, he ordered Jackson not to leave the studio until he sang the vocals for "Keep the Faith" all the way through: "This was scary but he did it. He didn't leave the studio until dawn."

Jackson spent \$10 million to record Dangerous. Executives at Epic set a deadline for the album, wanting it released before November 28, 1991, Thanksgiving Day. For the last two months of recording, Jackson and Swedien rented hotel rooms located four minutes from Record One, so they could get back to work as soon as possible. Riley said, "When the deadline came, [Jackson] wanted to do more and more songs. [...] And then when Michael saw the commercial for Dangerous, the David Lynch thing, we started working hard to get it finished." Dangerous was completed and mastered, by Bernie Grundman, on Halloween, 1991.

Jackson recorded roughly 60 to 70 songs for Dangerous, some of which were released later, including the environmental anthem "Earth Song", released on his next album, HIStory. "Superfly Sister," "Ghosts" and "Blood on the Dance Floor" were released in the remix compilation Blood on the Dance Floor: HIStory in the Mix. Loren helped develop "Superfly Sister", while Riley worked on "Ghosts" and "Blood on the Dance Floor". "For All Time", a romantic pop ballad that Jackson liked but did not feel it fit Dangerous, was released in the 25th anniversary edition of Thriller. "Slave to the Rhythm" was remastered and released for the 2014 compilation album Xscape. Another Riley outtake, "Joy", featured in Blackstreet's 1994 debut album, which Riley produced.

## Composition and lyrics

Dangerous is a new jack swing, R&B and pop album, which incorporates elements of several other genres, including industrial, funk, hip hop, electronic, gospel, classical, and rock. In a 1992 interview with Ebony magazine, Jackson said, "I wanted to do an album like Tchaikovsky’s Nutcracker Suite. So that in a thousand years from now, people would still be listening to it." Much of the album contains samples from CDs that Riley had created himself using a variety of instruments.

The album features catchy pop hooks and choruses while also introducing underground sounds to a mainstream audience. The album's tone is noted by critics as gritty and urban, with sounds including synthetic basslines, scratching, and drum machine percussion, as well as unconventional sounds like honking vehicle horns, sliding chains, swinging gates, breaking glass, and clanking metal. Throughout the album Jackson also implements beatboxing, scat singing, and finger snapping. The album is considered by Joe Vogel in PopMatters to be an artistic change for Jackson, because of its focus on socially conscious material, and a broader range of sounds and styles. The car sound effects on "She Drives Me Wild" were taken from a sample CD, and was the first time Riley used unusual sounds in place of the drums on a song.

The album featured Jackson rapping for the first time. The inclusion of Wreckx-n-Effect and hip-hop rhythms were attempts to introduce Jackson to a younger generation of urban listeners. Riley was a pioneer of new jack swing, and he was hired by Jackson specifically for his work in the genre. Riley co-produced half the songs on the album. Swedien said of Riley, "He'd come in with a groove, we'd say it wasn't exactly right, and there would be no complaining. He'd just go back and then come back in and blow us away with something like 'Dangerous'." In recordings with Bottrell, the sounds were more diverse (e.g. "Black or White" and "Give In to Me"). The rap in "Black or White" was written and performed by Bottrell, credited under the pseudonym "L.T.B." Jackson hummed melodies and grooves before leaving the studio, while Bottrell developed on these ideas with drum machines and samplers, including an Akai S1000. Bottrell operated a Neve console and two 24-track Studer analog tape machines to draft ideas and demos. He then used a 32-track Mitsubishi machine to assemble the album.

The lyrics for Dangerous were more varied than those of Jackson's previous records. Opening track "Jam" features a dense, swirling Riley track, propelled by horn samples and a subtle scratch effect. Jackson had recorded a basic idea for the song on a DAT, to which he asked Riley to develop. Riley learned that Heavy D was Jackson's favourite rapper at the time, and suggested that he was brought in to contribute a rap. The ballads, "Keep the Faith" (composed by Jackson, Siedah Garrett and Glen Ballard) and the self-composed "Will You Be There" had sounds of gospel, while "Heal the World" and "Gone Too Soon" were softer pop ballads. "Gone Too Soon", written by Larry Grossman and Buz Kohan, is a tribute to Ryan White following his death due to AIDS in 1990. The album also includes songs of other personal nature, especially in songs such as "She Drives Me Wild", "Remember the Time", "Can't Let Her Get Away", "Who Is It" and "Give In to Me". The title track's subject is similar to that of "Dirty Diana" with the song focusing on a seductress. Though Jackson sang about racial harmony in some of his songs with the Jacksons, "Black or White" was the first song where the lyrics were interpreted with the context of his own changing skin color. In "Why You Wanna Trip on Me," Jackson juxtaposed social ills to his own alleged eccentricities that were covered in the press at the time, asking critics and the tabloid media why they were focusing on the cult of celebrity rather than the multitude of serious problems in the world. Riley performed the guitar parts on an Ovation acoustic, and expected Jackson to have someone brought in to re-record them, but was surprised that Jackson liked what he had put down.

## Artwork

The album's front cover was painted by American pop surrealist artist Mark Ryden. It displays Jackson behind a gold masquerade mask with the face of a chimpanzee (which may be Jackson's pet Bubbles) atop the mask, and a dog and a bird wearing royal clothing sitting on the left and right side, respectively. The forefront depicts P. T. Barnum, the creator of the Barnum and Bailey circus. Ryden had five days to come up with ideas, and "feverishly worked that week" to produce one design per day. He was instructed to focus on Jackson's eyes, include animals and children, and "show the earth at peril". He was also told that his designs "could be scary, but should still be fun". Ryden said the cover was his most exciting project up to that point. In November 2021, the 30th anniversary of Dangerous, Ryden shared his conceptual drawings for the cover on Instagram for the first time. According to Fraser McAlpine of BBC Music, Ryden depicted Jackson as "a guarded circus artist who has seen glory and the machinery involved in making it happen".

## Events leading to release

In November 1991, days before the debut of the music video "Black or White", David Browne of Entertainment Weekly commented on the high expectations of Dangerous, due to the extended time spent on developing the album and Jackson's lucrative \$65 million contract with Sony Music. The writer stated, "[T]here is more riding on the success of Dangerous than on any other album in pop history." Jackson personally hoped that the album would sell 100 million copies, a number that would twice surpass the sales of Thriller. Five days before the album's release, three men armed with guns robbed 30,000 copies from a Los Angeles warehouse.

## Release and commercial reception

Dangerous was released on November 26, 1991. It debuted at number one on the Billboard 200 Top Albums chart on December 14, 1991, and spent an additional three weeks there. In the first week, it sold 326,500 copies, debuting at \#1. In the second week, the album remained at \#1, selling 378,000 copies, a 16% increase from the previous week sales. In its third week, Dangerous sold 370,000 copies and still remained at \#1. At the end of 1991, the total number of sales totalled to 1,074,500 copies sold in the United States and the album was certified platinum. Dangerous opened the year 1992, dated January 4, remaining at \#1 with 370,000 copies sold. By January 1992, it was certified four-times platinum by the Recording Industry Association of America (RIAA) for sales of over four million copies in the United States, roughly the same number as the initial sales of Off the Wall.

Dangerous continued to sell strongly in 1992 and 1993 in the US. In 1993, following several personal and promotional appearances, album sales for Dangerous grew significantly. Following Jackson's performance at the Inauguration of U.S. President Bill Clinton, sales increased 36% and the album jumped from 131 to 88 on the week of February 6, 1993. In the next week, sales increased 83% and the album jumped to 41 following his appearance on the American Music Awards 1993 where he won 3 awards. Sales increased 40% in the following week due to the historic ratings of the Halftime Super Bowl performance and the album jumped again from 41 to 26 on the Billboard 200 selling over 29,000. On the week of February 27, 1993, album sales increased again because of the strong ratings due to the "Michael Jackson Talks ... to Oprah" TV special, selling close to 60,000 units and jumping from 26 to 12. In the following week, the album finally reentered the top 10 in the United States. As of December 1993, sales for Dangerous were around 4.8 million copies. In August 2018, the album was certified eight-times platinum by the RIAA for sales of over 8 million copies.

In Europe, it was reported that the album reached 4 million copies in shipments before it was released, becoming an all-time record at the time. It dominated global charts, debuting at number one in the U.K. while also reaching number one in twelve other territories including Australia, France, Germany, the Netherlands and Spain.

Due to the massive success of the Dangerous World Tour, album sales for Dangerous received a boost. In the first four weeks of his tour in 1992, sales of Michael Jackson's Dangerous album increased from 6.8 million to 7.2 million units in Europe.

Worldwide, the album was a massive success in fourteen countries. The album sold 5 million copies in its first week of been released outside the United States. It reached the 10 million mark in sales in the first two months after its release; Jackson's two previous albums, "Bad" and "Thriller," each took more than four months to achieve that goal.

By November 1992, the album had reportedly sold 15 million copies worldwide and was the best-selling album of that year internationally. By recent estimates, Dangerous has sold over 32 million copies worldwide making it one of the best-selling albums of all time.

## Promotion

Similar to the way in which record label executives had approached Bad, expectations were set at a high bar for Dangerous. In September 1991, Jackson netted a deal to have his videos air on FOX alongside regular music-video channels MTV, BET and VH1.

The eleven-minute video for "Black or White" debuted on November 14, 1991, and was broadcast across 27 countries. Five hundred million viewers reportedly watched it—the largest audience ever for a music video. The music video and its controversy boosted the sale of Dangerous, as did the broadcast of videos for "Remember the Time" and "In the Closet". The Dangerous: The Short Films collection of music videos from Dangerous, with behind-the-scenes footage, was released in 1993.

Jackson embarked on the Dangerous World Tour, which grossed \$100 million (equivalent to \$177 million in 2020) and drew nearly 4 million people across 72 concerts. All profits from the tour were donated to charities including Jackson's Heal the World Foundation. The Bucharest concert was filmed on October 1, 1992, for broadcast on HBO on October 10, 1992. Jackson sold the film rights for the concert for \$20 million, then the highest amount for a concert performer to appear on television. The airing of the HBO concert special, Michael Jackson: Live in Bucharest, revived sales of the album.

Jackson made personal appearances in early 1993, including the American Music Awards and Grammy Awards, when he accepted the Grammy Legend Award from his sister Janet. He also filmed a widely discussed interview with Oprah Winfrey and made a half-time performance at the Super Bowl XXVII, which started the NFL's trend of signing top acts to appear during the Super Bowl to attract more viewers and interest. The performance helped return Dangerous to the US album chart's top ten. In August 1993, as the third leg of the Dangerous World Tour began, the first allegations of child sexual abuse against Jackson became public and received worldwide media attention. In November, Jackson canceled the remainder of the tour, citing health problems arising from the scandal.

## Singles

The lead single, "Black or White", was released in November 1991, reaching the top of the Billboard Hot 100 chart three weeks after it was released and staying there for seven weeks. It was the fastest chart-topper since the Beatles' "Get Back" in 1969 and the best-selling single worldwide of 1992. "Black or White" reached number one in 20 countries, including the US, the UK, Canada, Mexico, Cuba, Turkey, Zimbabwe, Australia, New Zealand, Belgium, Denmark, Finland, France, Ireland, Israel, Italy, Norway, Spain, Sweden, Switzerland and the Eurochart Hot 100. It became the first American single to enter the UK Singles Chart at number one since "It's Now or Never" by Elvis Presley in 1960. The singles were more successful overseas than in the US. In the UK alone, seven singles reached the top ten. This set a record for any studio album in the UK until Calvin Harris surpassed it in 2013.

"Remember the Time" peaked at number three on the Billboard Hot 100 singles chart and number one on the R&B Singles Chart. It reached number one in New Zealand charts for two consecutive weeks. In the United Kingdom, the song charted at number three, where it peaked. It peaked at number four in the Netherlands and Switzerland. The song also charted within the top ten on the French, Australian, Swedish, Italian, and Norwegian charts; peaking at number five, six, eight and ten. It charted in the top 20, peaking at number 16, in Austria. It was generally well received by contemporary music critics and regarded as one of the highlight songs on Dangerous.

The album's third single, "In the Closet" peaked at number six on the Billboard Hot 100, also reached number one on the R&B Singles Chart, becoming the album's third consecutive top 10 hit. In the United Kingdom, the song charted at number eight, where it peaked. The song's female vocal was originally labeled "Mystery Girl" but was later revealed to be Princess Stéphanie of Monaco.

"Jam" only reached number 26 on the Billboard Hot 100, despite heavy promotion. The music video of the song featured NBA icon Michael Jordan. The song was played in the Chicago Bulls' 1992 NBA Championship video Untouchabulls and was used in many promotional NBA ads of that season. In the UK, the single reached the top twenty, where it peaked at number 13.

"Heal the World" peaked at number 27 on the Billboard Hot 100. The song reached number two in the UK Singles Chart in December 1992, kept off the number one position by Whitney Houston's "I Will Always Love You". In a 2001 Internet chat with fans, Jackson said "Heal the World" was the song he was most proud to have created.

"Who Is It" peaked at number 14 on the United States' Billboard Hot 100, while peaking at number six on Billboard Hot R&B/Hip-Hop Songs, as well as topping the Hot Dance Club Play. The song peaked on the United Kingdom music chart at number ten. It remained within the top 100 positions for seven consecutive weeks from July to September 1992. In France, the track peaked at number eight on August 29. "Who Is It" reached its lowest peak position at number 34 in Australia.

"Will You Be There" was the last top-10 single on the Billboard Hot 100 from the album, peaking at number seven. The song peaked at number two in New Zealand and reaching the top ten in Belgium, Canada, Ireland, the Netherlands, Switzerland and the United Kingdom. It was the theme song of the film Free Willy. Its appearance in the film also helped sales for Dangerous.

The overseas-only single "Give In to Me" reached the top five in the UK, Netherlands and Australia, while hitting the top of the charts in New Zealand.

"Gone Too Soon", another overseas single, was more moderately received, charting within the top 40 in the UK. Jackson performed the song at president-elect Bill Clinton's inauguration celebration An American Reunion: The 52nd Presidential Inaugural Gala.

## Critical reception

Dangerous received critical praise upon release. In a review for Rolling Stone, Alan Light said Jackson was "a man, no longer a man-child, confronting his well-publicized demons and achieving transcendence through performance", on an album that rose to "the impossible challenge set by Thriller during moments when Riley's production dance rhythms "prove a perfect match for Jackson's clipped, breathy uptempo voice".

Robert Christgau of The Village Voice deemed it Jackson's "most consistent album since Off the Wall, a step up from Bad even if its hook craft is invariably secondary and its vocal mannerisms occasionally annoying." While he felt Jackson was too insistent with the "faith-hope-and-charity" message songs, Christgau applauded the production's "abrasively unpredictable" rhythms and the "sex-and-romance" songs, calling them the most plausible of Jackson's career.

Jon Pareles was less receptive in The New York Times, calling it Jackson's "least confident" solo album yet. He believed Jackson sounded anxious and out of place with Riley's electronic beats while panning the "dogmatically ordinary" lyrics of the love songs, writing that "they seem based on demographic research rather than experience or imagination". Chris Willman, writing for the Los Angeles Times, said, on the album, Jackson wanted to transcend all demographics—race, age, nationality—and be a role model for children and a bad cat at the same time. The album was "mostly good, expertly made fun" but far from Jackson's best work. Willman also criticized "Heal the World" as "goofily embarrassing" and "venturing into the realm of self-parody".

Dangerous received four Grammy Award nominations including three for Jackson: Best Pop Vocal Performance for "Black or White", and Best R&B Vocal Performance and Best R&B Song for "Jam". Teddy Riley and Bruce Swedien won Best Engineered Album, Non Classical, while Jackson received the Grammy Legend Award in the same ceremony. Jackson won two awards and received five nominations total at the 1993 American Music Awards. Dangerous won Favorite Pop/Rock Album, and "Remember the Time" won Favorite Soul/R&B Song. The inaugural International Artist Award also went to Jackson.

Jackson won Best R&B/Soul Album of the Year – Male and Best R&B/Soul Single – Male for "Remember the Time" at the 1993 Soul Train Music Awards. He also won the special Humanitarian Award. At the 1993 NAACP Image Awards, "Black or White" won Outstanding Music Video, and Jackson won the Entertainer of the Year Award. At the 1994 MTV Movie Awards, "Will You Be There" won Best Song From a Movie. The 1992 Billboard Music Awards awarded Jackson Best Worldwide Album for the album and Best Worldwide Single for "Black or White". Both were special awards.

## Legacy and influence

### Reappraisal

An influence on contemporary pop and R&B artists, Dangerous has been ranked by critics and publications as one of the greatest albums of all time. While the sounds on the album polarized critics, some have considered Dangerous as Jackson's artistic peak. Jeff Weiss called it "Jackson’s final classic album and the best full-length of the New Jack Swing era." Critic Joseph Vogel described the album as Jackson's most socially conscious record, most personally revealing—similar to Stevie Wonder's Songs in the Key of Life—and the most groundbreaking record of its era. He added "Dangerous is gaining admirers as more people move beyond the extraneous nonsense that was so prominent in contemporaneous reviews and pay attention to its content: its prescient themes, its vast inventory of sounds, its panoramic survey of musical styles...His R&B-rap fusions set the blueprint for years to come, while his industrial soundscapes and metallic beats were later popularized by artists as disparate as Nine Inch Nails and Lady Gaga". Writing for The Guardian in 2018, the critic said, "Returning to [Dangerous] now, without the hype or biases that accompanied its release in the early 90s, one gets a clearer sense of its significance [...] it surveyed the cultural scene—and the internal anguish of its creator—in compelling ways [...]. The contemporary music scene is certainly far more indebted to Dangerous". Vogel also credited the album as a significant factor to the transformation of Black music. Ben Beaumont-Thomas deemed Dangerous as Jackson's career-high album, "the very peak of his powers, with his widest ever emotional range set to production that makes new jack swing seem much more than just lame dance moves and fluorescent man-made fibers." Stephen Thomas Erlewine also praised Jackson's brave approach in the album, that it was "a much sharper, riskier album" than Bad.

Speaking for the Rock and Roll Hall of Fame, Janet Macoska applauded the modernity of Dangerous: "a sleek, contemporary-sounding update of Jackson's music" which featured the "ambitious, heartfelt anthems "Heal The World" and "Will You Be There." Similarly, Odyssey critic James Wesser said, "[Dangerous], in my opinion, is timeless and if it was re-released in the year 2016, it will still sound fresh and new." Michael Roffman of Consequence of Sound described the album as "Jackson's 90s masterpiece." Scholar Susan Fast thought of Dangerous as Jackson's coming-of-age album: “[The album] offers a compelling narrative arc of postmodern angst, love, lust, seduction, betrayal, damnation, and above all else racial politics, in ways heretofore unseen in his music." Meanwhile, Tari Ngangura of Vice described it as one of the "greatest introspective albums of all time." Todd "Stereo" Williams of The Boombox said the album was Jackson's "blackest album" since Off the Wall—a return to his roots. He highlighted the cultural references in the music video "Black or White," the all Black cast and Black director for "Remember the Time," the casting of Black supermodel Naomi Campbell as the love interest in "In the Closet" and working with Teddy Riley, who was "R&B's biggest hit-maker" at the time. Williams also considered the album as a significant record of the 90s; it asserted Jackson as a formidable force in popular music amid the rise of grunge and gangsta rap.

### Rankings

In 2007, the National Association of Recording Merchandisers (NARM), in conjunction with the Rock and Roll Hall of Fame, ranked Dangerous at number 115 on its list of the Definitive 200 Albums of All Time. In Spins list of The 300 Best Albums of the Past 30 Years (1985–2014), the album was ranked at number 132. Spin writer Chuck Eddy named it one of the essential new jack swing albums in a list published by the magazine. In Colin Larkin's third edition of the All Time Top 1000 Albums (2000), Dangerous was ranked number 325. Additionally, it was ranked number 13 in the list of the Soul/R&B – All Time Top 50 albums. Dangerous was ranked number 43 in Billboard's list of the Greatest of All Time R&B/Hip-Hop Albums, out of 100 albums. In 2019, 24/7 Wall St. ranked it number 89 in its list of the 100 Best Pop Albums of All Time.

### Accolades

## Track listing

Credits adapted from the album's CD booklet

Notes'''

- signifies a co-producer

## Personnel

Personnel as listed in the album's liner notes.

- John Bahler – vocal and choir arrangements (track 7)
- The John Bahler Singers – choir (track 7)
- Glen Ballard – arrangements (track 12)
- John Barnes – keyboards (track 8)
- Michael Boddicker – synthesizer (tracks 1, 7, 11–13), sequencer (8), keyboards and programming (9)
- Bill Bottrell – producer, engineer, and mixing (tracks 8–10); guitar (8, 10); drums (9, 10); percussion, rap, and intro voice-over (8); synthesizer (9); bass guitar and mellotron (10)
- Craig Brock – assistant guitar engineer (track 10)
- Brad Buxer – keyboards (tracks 1, 7–9, 11), synthesizer (1, 14), percussion (8), programming (9)
- Larry Corbett – cello (track 9)
- Andraé Crouch – choir arrangements (tracks 11, 12)
- Sandra Crouch – choir arrangements (tracks 11, 12)
- The Andraé Crouch Singers – choir (tracks 11, 12)
- Heavy D – rap (track 1)
- George Del Barrio – string arrangements (track 9)
- Matt Forger – engineer and mixing (track 7), engineering and sound design (8 intro)
- Kevin Gilbert – speed sequencer (track 8)
- Endre Granat – concertmaster (track 9)
- Linda Harmon – soprano voice (track 9)
- Jerry Hey – arrangements (track 12)
- Jean-Marie Horvat – engineer (track 14)
- Michael Jackson – producer and lead vocals (all tracks), background vocals (1–12, 14), arrangements (1, 9), vocal arrangements (1, 3–7, 11, 14), rhythm arrangements (7, 11), director (8 intro), soprano voice (9)
- Paul Jackson Jr. – guitar (track 2)
- Terry Jackson – bass guitar (track 8)
- Louis Johnson – bass guitar (track 9)
- Abraham Laboriel – bass guitar (track 13)
- Christa Larson – ending solo vocal (track 7)
- Rhett Lawrence – synthesizer (tracks 1, 11, 12, 14); drums, percussion, and arrangements (12); synthesizer programming (11)
- Bryan Loren – drums (track 8, 9), synthesizer (8)
- Johnny Mandel – orchestral arrangements and conductor (track 11)
- Jasun Martz – keyboards (track 8)
- Andres McKenzie – intro voice-over (track 8)
- Jim Mitchell – guitar engineer (track 10)
- René Moore – arrangements and keyboards (track 1)
- David Paich – keyboards (tracks 7, 9, 13), synthesizer (7, 13), keyboard arrangements and programming (9), rhythm arrangements (13)
- Marty Paich – orchestral arrangements and conductor (tracks 7, 13)
- Greg Phillinganes – keyboards (track 11)
- Tim Pierce – heavy metal guitar (track 8)
- Jeff Porcaro – drums (track 7)
- Steve Porcaro – synthesizer (tracks 7, 13), keyboards and programming (9)
- Teddy Riley – producer, engineer, mixing, and synthesizers (tracks 1–6, 14); keyboards (1–6); guitar (1, 2); rhythm arrangements (2–6, 14); synthesizer arrangements (3–6, 14); drums and arrangements (1)
- Thom Russo – engineer (track 14)
- Slash – special guitar performance (track 10)
- Bruce Swedien – producer (track 1), co-producer (tracks 7, 11–13), engineer and mixing (1–7, 11–14), arrangements and keyboards (1), drums (1, 11, 12), percussion (11, 12)
- Jai Winding – keyboards and programming (track 9), piano and bass guitar (12)
- Mystery Girl (Princess Stéphanie of Monaco) – vocals (track 3)

## Charts

### Weekly charts

### Year-end charts

### Decade-end charts

## Certifications and sales

## See also

- Dangerous World Tour
- Live in Bucharest: The Dangerous Tour
- Dangerous – The Short Films''
- List of best-selling albums
- List of best-selling albums by country
- List of best-selling albums in Australia
- List of best-selling albums in Chile
- List of best-selling albums in Europe
- List of best-selling albums in France
- List of best-selling albums in Germany
- List of best-selling albums in Indonesia
- List of best-selling albums in Italy
- List of best-selling albums in Mexico
- List of best-selling albums in Taiwan
- List of number-one albums of 1991 (U.S.)
- List of number-one albums of 1992 (U.S.)
- List of number-one R&B albums of 1992 (U.S.)

Albums recorded at United Western Recorders

Albums recorded at Westlake Recording Studios

Grammy Award for Best Engineered Album, Non-Classical


Hurricane Lenny

Hurricane Lenny was the strongest November Atlantic hurricane since the 1932 Cuba hurricane. It was the twelfth tropical storm, eighth hurricane, and record-breaking fifth Category 4 hurricane in the 1999 Atlantic hurricane season. Lenny formed on November 13 in the western Caribbean Sea at around 18:00 UTC and went on to form and maintain an unusual and unprecedented easterly track for its entire duration, which gave it the common nickname, "Wrong Way Lenny". It attained hurricane status south of Jamaica on November 15 and passed south of Hispaniola and Puerto Rico over the next few days. Lenny rapidly intensified over the northeastern Caribbean on November 17, attaining peak winds of 155 mph (249 km/h) about 21 mi (34 km) south of Saint Croix in the United States Virgin Islands. It gradually weakened while moving through the Leeward Islands, eventually dissipating on November 23 over the open Atlantic Ocean.

Before moving through the Lesser Antilles, Lenny produced rough surf that killed two people in northern Colombia. Strong winds and rainfall resulted in heavy crop damage in southeastern Puerto Rico. Despite the hurricane's passage near Saint Croix at peak intensity, damage on the small island was only described as "moderate", although there was widespread flooding and erosion. Damage in the United States territories totaled about \$330 million. The highest precipitation total was 34.12 in (867 mm) at the police station on the French side of Saint Martin. On the island, the hurricane killed three people and destroyed more than 200 properties. In nearby Antigua and Barbuda, the hurricane killed one person; torrential rainfall there contaminated the local water supply. Significant storm damage occurred as far south as Grenada, where high surf isolated towns from the capital city.

## Meteorological history

Hurricane Lenny began as a low-pressure area that was first observed in the southwestern Caribbean Sea on November 8. It developed an area of convection but remained poorly defined for the next few days. Thunderstorms spread across the region, producing heavy rainfall in portions of Mexico and Central America. On November 13, the system became better organized; a Hurricane Hunters flight later that day discovered a surface circulation and winds of about 35 mph (56 km/h). The data indicated the development of Tropical Depression Sixteen at 1800 UTC, about 175 mi (282 km) south of the Cayman Islands. The depression's convection was fairly disorganized, and the National Hurricane Center (NHC) did not anticipate any strengthening for three days. For much of its existence, the tropical cyclone maintained a track from west to east across the Caribbean Sea, which was unprecedented in the Atlantic hurricane database, earning it the nicknames "Left-Hand Lenny" and "Wrong Way Lenny". The path resulted from its movement along the southern end of a trough over the western Atlantic Ocean.

After its formation, the depression gradually became better organized; the NHC upgraded it to Tropical Storm Lenny on November 14, based on reports from the Hurricane Hunters. When it was first upgraded to a tropical storm, the cyclone already had winds of 65 mph (105 km/h) and a developing eye feature. At 0000 UTC on November 15, Lenny attained hurricane status about 175 mi (282 km) southwest of Kingston, Jamaica. The quick intensification was unexpected and occurred after a large area of convection blossomed over the center. At the same time, Lenny developed an anticyclone aloft, which provided favorable conditions for the hurricane's development. After moving east-southeastward during its initial development stages, the hurricane turned more to the east on November 15. The Hurricane Hunters reported winds of 100 mph (160 km/h), which indicated that Lenny had become a Category 2 on the Saffir-Simpson Hurricane Scale. However, the cloud pattern subsequently became less organized as the eye disappeared, and Lenny's winds weakened to 85 mph (137 km/h) while the hurricane passed south of Hispaniola. The NHC noted the deterioration could have been due to a disruption of the storm's small inner core by "subtle environmental changes". After the sudden weakening, the Hurricane Hunters reported that the eye had reformed and the hurricane's winds had reached 100 mph (160 km/h). At the time, a ridge was expected to build to Lenny's east and turn the storm northeastward into Puerto Rico 24 hours later.

Beginning on November 16, Hurricane Lenny underwent a 24-hour period of rapid deepening, reaching major hurricane status about 165 mi (266 km) south of the Mona Passage. It developed well-defined banding features, good outflow, and a circular eye that was visible from the radar in San Juan, Puerto Rico. The hurricane continued to become better organized, with an eye 29 mi (47 km) in diameter surrounded by a closed eyewall. Around 1200 UTC on November 17, Lenny intensified into a Category 4 hurricane while approaching the islands of the northeastern Caribbean. It was the fifth storm of such intensity in the year, setting the record for most Category 4 hurricanes in a season. The hurricane then made its closest approach to Puerto Rico, passing about 75 mi (121 km) southeast of Maunabo. Shortly thereafter, Lenny attained peak winds of 155 mph (249 km/h) while passing 21 mi (34 km) south of the island of Saint Croix in the United States Virgin Islands. This made it the fourth-strongest hurricane on record to form during the month of November. Hurricane Hunters reported Lenny's peak winds in the southeastern portion of the hurricane; the group also reported a minimum pressure of 933 mbar, a drop of 34 mbar in 24 hours. In addition, a dropsonde recorded winds of 210 mph (340 km/h) while descending to the surface, the highest dropsonde wind speed recording in a hurricane at the time.

Around the time it peaked in intensity, Lenny's forward speed decreased in response to light steering currents between two ridges. Despite favorable conditions for strengthening, the hurricane weakened as it turned to an eastward drift, possibly due to the upwelling of cooler waters. Late on November 18, Lenny's eye moved over Saint Martin with winds of 125 mph (201 km/h). After continued weakening, the hurricane struck Anguilla and Saint Barthélemy the next day. It turned southeastward while still drifting, bringing heavy rainfall and strong winds to the islands across the northeastern Caribbean. Late on November 19, Lenny weakened to tropical storm intensity after increased wind shear exposed the cyclone's center from the deepest convection. Early on November 20, the storm made landfall on Anguilla, although by then the center had become difficult to locate. Later that day, the cyclone exited the Caribbean, continuing its southeast track. On November 21, Lenny turned to the northeast and weakened to a tropical depression. The deep convection was located at least 100 mi (160 km) east of the increasingly elongated center. Lenny turned to the east for the final time early on November 22, dissipating on the next day about 690 mi (1,110 km) east of the Lesser Antilles.

## Preparations

Early in Lenny's existence, a tropical storm warning and hurricane watch were issued for Jamaica. Later, a hurricane watch was issued for the southern coast of Hispaniola, and a tropical storm warning was also issued for the Dominican Republic. Haitian officials declared a state of alert in three southern provinces and allocated about \$1 million (1999 USD) in hurricane funds. Residents in flood-prone areas were advised to evacuate in southern Haiti and in the neighboring Dominican Republic.

A hurricane watch was issued for Puerto Rico and the Virgin Islands late on November 15, which was upgraded to a hurricane warning six hours later. By that time, Lenny was projected to move over Puerto Rico. After Lenny made its closest approach to the island, the hurricane warning was downgraded to a tropical storm warning on November 17, which was discontinued the following day along with the advisories in the Virgin Islands. In Puerto Rico, the media maintained continuous coverage on the hurricane based on statements and warnings from the San Juan National Weather Service office. Based on the coverage, the public was well informed of the hurricane's threat to the island. Before the storm and as a result of its impact, around 4,700 people evacuated to 191 shelters. This included 1,190 residents in Ponce who evacuated to 27 schools, as well as 584 people in western Puerto Rico. Officials closed all schools, banned the sale of alcohol, and ordered a freeze on the price of emergency supplies. The Federal Emergency Management Agency (FEMA) activated six medical assistance teams, three medical support teams, and two advance medical assessment units. The agency stored five days' worth of food in schools in the U.S. Virgin Islands. Before the hurricane's arrival, U.S. Virgin Islands governor Charles Wesley Turnbull declared a state of emergency. In St. Croix, 309 people rode out the storm in shelters. Officials opened eight shelters in the British Virgin Islands. There, airlines and hotels assisted in evacuating tourists from the area.

Governments across the eastern Caribbean issued hurricane warnings as far south as Montserrat. In Anguilla, residents near the coast were advised to evacuate. Schools closed ahead of the storm, and the ferry between the island and Saint Martin was halted and moved to a safe location. In Saint Kitts and Nevis, the National Emergency Management Agency was activated on November 16. Officials there advised residents living near ghauts to evacuate, and one shelter was located in each district of the country. In addition, stores were open for longer hours to allow people to stock up on supplies. Most businesses and schools were closed in Antigua and Barbuda during the storm, while in Dominica, the airport was closed. Further south, there was little warning for the hurricane in Grenada, and most people left their boats in the water.

## Impact

Across the eastern Caribbean, Hurricane Lenny damaged vital infrastructure, including roads and piers in the tourism-dependent islands. Most of the islands' tourism areas were on western-facing beaches, many of which were unprepared for the high waves and winds produced by Lenny.

### Central Caribbean

Early in its existence, Lenny produced large waves and high tides along the Guajira Peninsula in Colombia, sinking two boats and flooding 1,200 houses. There were also reports of flooded businesses and damaged crops. In the country, strong winds on the storm's fringe killed a man by striking him with a beam. Although there were initial reports of nine people missing, only two were counted in the death toll for mainland Colombia. Two sailors were killed offshore when their yacht was lost in the southern Caribbean Sea.

Along the ABC Islands off the north coast of Venezuela, the hurricane produced 10-to-20 ft (3-to-6 m) waves along the southwest coastlines. The waves caused heavy beach erosion and coastal damage to properties and boats.

In Jamaica, the hurricane dropped heavy rainfall but left little damage. Rains in the Dominican Republic caused flooding in the country's southwest portion. Flooding around Les Cayes in southwestern Haiti destroyed 60 percent of the rice, corn, and banana plantations, while high waves wrecked several houses in Cavaellon.

Hurricane Lenny was originally forecast to strike Puerto Rico, although it remained south of the island. Beginning on November 17, Lenny affected Puerto Rico with gusty winds and heavy rainfall. Rainfall in the days prior to Lenny's approach left areas susceptible to flooding, which caused many rivers in the northeastern portion of the island to overflow their banks following the storm. Such flooding forced towns to evacuate along the rivers, and also resulted in the closure of secondary and primary highways. The heavy rains also caused mudslides and rockslides. The peak rainfall on the island was 14.64 in (372 mm) in Jayuya in central Puerto Rico. Tides in San Juan were about 1.8 ft (0.55 m) above normal. There, high seas washed a 546 ft (166 m) freighter ashore. Winds in the Puerto Rican mainland were not significant, gusting to 48 mph (77 km/h) in Ceiba. The storm left 22,000 people without power and 103,000 people without water. Because of the heavy rainfall, about 200 farmers in southeastern Puerto Rico sustained about \$19 million in crop damage (1999 USD). In the affected region, the heavy rainfall destroyed 80 percent of the vegetables and 50 percent of the plantains. Damage throughout the island totaled \$105 million (1999 USD).

### Virgin Islands

After passing southeast of Puerto Rico, Hurricane Lenny struck St. Croix in the United States Virgin Islands, although its strongest winds remained southeast of the island. There, gusts reached 112 mph (180 km/h), while sustained winds officially peaked around 70 mph (110 km/h). Strong winds damaged the roofs of many houses in eastern St. Croix and knocked down trees and power lines. The winds left severe damage to vegetation after fruits and vegetables were blown away. Rainfall peaked at 10.47 in (266 mm), which caused widespread flooding of many properties in the island's western portion. In Frederiksted, the hurricane produced a storm surge of 15–20 ft (4.6–6.1 m) along with high waves that washed out roads and damaged coastal structures. There was also severe beach erosion in western St. Croix; high waves dumped 6.5 ft (2.0 m) of sand onto coastal roads about 100 ft (30 m) inland, and also washed several boats ashore. The National Weather Service described the damage as "moderate".

Elsewhere in the U.S. Virgin Islands, Lenny produced a storm surge of about 1.8 ft (0.55 m) in St. Thomas. Sustained winds on the island reached 53 mph (85 km/h) at the Cyril E. King Airport, with gusts to 70 mph (110 km/h). On nearby St. John, wind gusts reached 92 mph (148 km/h), and sustained hurricane-force winds of 83 mph (134 km/h) were reported on Maria Hill. Rains were not as heavy as on St. Croix; the maximum amounts were 4.34 in (110 mm) on St. Thomas and 2.95 in (75 mm) on St. John. Both islands reported beach erosion along their southern coastlines. Damage on St. Thomas was minimal, limited to minor flooding and mudslides. The Virgin Islands National Park in St. John reported over \$1.6 million in damage (1999 USD). In Puerto Rico and the U.S. Virgin Islands, the hurricane left about \$330 million in damage (1999 USD), but caused no deaths.

In Virgin Gorda in the nearby British Virgin Islands, the hurricane produced sustained winds of 55 mph (89 km/h), with gusts to 85 mph (137 km/h). Rainfall amounted to around 4 in (100 mm) and caused a mudslide near Coxheath. High waves eroded a portion of Sir Francis Drake Highway, and the high winds destroyed the roof of an apartment. Property damage in the British Virgin Islands totaled \$5.6 million (1999 USD); however, the damage combined with the loss of tourism and productivity yielded a loss of \$22 million to the islands' economy, or 3.1 percent of the gross domestic product.

### Northern Leeward Islands

#### Anguilla

The eye of Lenny moved over Anguilla, an island located east of the British Virgin Islands. Localized flooding was reported, including in the capital, The Valley, where waters reportedly reached a depth of 14 ft (4.3 m). The hurricane struck only a month after Hurricane Jose had affected the region, causing significant beach erosion along Anguilla's coastline. Damage from Lenny amounted to \$65.8 million.

#### Saint Barthélémy and Saint Martin

On Saint Barthélemy, the hurricane produced record-breaking precipitation of around 15 in (380 mm). Waves reached 16 ft (4.9 m) on the island's western portion. The highest precipitation related to the storm occurred at the police station on the French side of Saint Martin, where a total of 34.12 in (867 mm) was recorded. This included a record 24-hour total of 18.98 in (482 mm). Total damage was extensive but not as extreme or catastrophic as Hurricane Luis in 1995.

#### The Dutch Antilles

The SSS Islands, which include Saba, Sint Eustatius, and Sint Maarten, were in the path of Hurricane Lenny on November 18 through 19. On Saba, there was an unofficial wind gust of 167 mph (269 km/h) before the instrument blew away. The island sustained damage to several buildings, including airport facilities. On the Dutch side of the island of Saint Martin, rainfall peaked at 27.56 in (700 mm) in Philipsburg. The rains resulted in mudslides and flooding and were the primary form of impact on the island. For 36 hours, the island experienced tropical storm conditions, and there were three times when the winds surpassed hurricane force. Sustained winds on the island peaked at 84 mph (135 km/h) at the Princess Juliana International Airport; these were the highest sustained winds observed on land. The airport also reported a wind gust of 104 mph (167 km/h). As a result, the three SSS Islands sustained power and telephone outages. There was widespread destruction of the roofs of houses across the island, and over 200 houses were destroyed. Damage was estimated at \$69 million, and there were three deaths on the Dutch side of St. Martin. Two of these deaths were from flying debris, and the other was due to a collapsed roadway.

Due to the hurricane's unusual track from the west, it produced unparalleled waves of 10–16 ft (3.0–4.9 m) along the western coast of St. Martin, which damaged or destroyed many boats. During its passage, Lenny left widespread damage to the infrastructure, including to the airport, harbor, resorts, power utilities, schools, and hospitals.

### Antigua and Barbuda

While passing over Antigua, Hurricane Lenny dropped 18.32 in (465 mm) of rain at the V. C. Bird International Airport, while locations in the southern portion recorded over 25 in (640 mm). The rainfall caused severe flooding in Antigua, resulting in landslides in the northwestern and southern portion of the island. Flooding washed out major roadways, including one bridge. Along the coast, the storm caused severe beach erosion. About 65 percent of Barbuda experienced flooding due to the rainfall and the island's flat topography. The flooding contaminated the water storage facilities and all private wells. About 95 percent of the crops in Barbuda were destroyed. Damage in the country of Antigua and Barbuda totaled \$51.3 million, and there was one death.

### Saint Kitts, Nevis and Montserrat

The hurricane's waves reached 20 ft (6.1 m) along the coasts of Saint Kitts and Nevis, washing up to 600 ft (180 m) inland. Several businesses were flooded, and some beach erosion was reported. The hurricane destroyed 46 homes and damaged 332 others to varying degree. Home damage forced four families to evacuate. Heavy rains caused mudslides on Saint Kitts, and heavy damage occurred in Old Road Town. Damage in the country amounted to \$41.4 million. In Montserrat, damage was reported along its western coastline. After high waves capsized a boat, a crew of three required rescue.

### Guadeloupe

Guadeloupe received record precipitation amounts in some areas, generally ranging from 6 to 19 inches (150 to 480 mm). On Basse-Terre, the western island of Guadeloupe, the hurricane produced a significant wave height of 9.8 ft (3.0 m), with estimates as high as 13 ft (4.0 m). There were five deaths, especially from drowning and electrocution in Guadeloupe and damage in the island totaled at least \$100 million.

Although there were no tropical-storm sustained wind recorded as the storm didn't really impacted the islands unlike previous hurricanes such as Luis, Marilyn and Georges, the extent of damage was globally heavier due to the unusual high waves in the western portion of the island and the very slow-moving storm that generated unrelated flooding inland in Grande-Terre for a 48 hour-period.

### Dominica

In Dominica, high waves damaged the island's western coastal highway, leaving the most heavily traveled road temporarily closed. Road closures cut off links between towns on the island. The hurricane destroyed at least 50 homes, including 3 that were washed away by the waves. Hotels along the island's west coast sustained heavy damage, and across the nation the hurricane's impact was worse than that from Hurricane Luis four years prior. Damage on the island totaled \$21.5 million.

### Windward Islands

Rainfall of around 3 in (76 mm) reached as far south as Martinique, where one person was killed. Further south, high waves in Saint Lucia washed away beaches, a seawall, and coastal walkways. At least 40 houses were damaged along the coast, which left several families homeless. Damage in the country totaled \$6.6 million. In Saint Vincent and the Grenadines, the hurricane washed away four buildings and damaged five others. About 50 people were left homeless in the country.

In western Grenada, high waves affected much of the coastline, destroying 21 small boats and causing significant beach erosion. The waves covered the entire Grand Anse Beach in Saint George Parish. The erosion heavily impacted tourist areas and also threatened the foundation of the runway at the Maurice Bishop International Airport. Storm damage cut off the towns in western Grenada from the capital city of Saint George's. The cut-off roads resulted in an island-wide fuel shortage. In Saint John Parish, the storm knocked out the water and power supply and forced several families to evacuate their damaged houses. The small island Carriacou, located north of Grenada, sustained damage to the road to its primary airport. At least 10 homes were destroyed in the country, and damage totaled \$94.6 million; this represented 27 percent of the island's gross domestic product. Effects from the storm reached as far south as Trinidad and Tobago. In the country, storm surge caused damage to boats and coastal structures, while beach erosion was reported in Tobago.

## Aftermath

Following heavy damage to the coral reef around Curaçao, workers placed reef balls to assist in replenishing the damaged structure. In Puerto Rico, workers quickly responded to power and water outages. Similarly on Saint Croix, power systems were quickly restored. On November 23, U.S. President Bill Clinton declared the U.S. Virgin Islands a disaster area. This allocated federal funding for loans to public and private entities and provided 75 percent of the cost of debris removal. By December 10, nearly 3,000 residents had applied for assistance, mostly on St. Croix. In response, the federal government provided about \$480,000 to the affected people. The United States Office of Foreign Disaster Assistance provided \$185,000, mostly directed toward the United Nations Development Programme, for aid to other islands in the eastern Caribbean. Other agencies, including the Caribbean Development Bank, the United Kingdom's Department for International Development, and the European Union, provided \$1.1 million in assistance.

In response to the damage on Saint Martin, officials in the Netherlands Antilles issued an appeal to the European Parliament for assistance from the international community. Due to their small population and area, the small islands of the eastern Caribbean required international funding to repair the damage from the hurricane and return to normal. In Antigua and Barbuda, officials worked quickly to repair roads and clean Barbuda's water system. However, 20,000 people in Antigua remained without water for a week after the hurricane, and the stagnant water caused an increase in mosquitoes. The government of Dominica provided 42 families with temporary shelters. With a loan from the Caribbean Development Bank, the government worked to complete a sea wall along a highway south of its capital Roseau. The Saint Lucian government provided housing to 70 families. In Grenada, workers repaired the road system to allow fuel transportation across the island and began to reclaim land near its airport to mitigate erosion. Regions in Antigua and Grenada were declared disaster areas. Across the eastern Caribbean, local Red Cross offices provided food and shelter to affected citizens. High damage to tourist areas caused a decrease in cruise lines. A damaged hotel in Nevis left 800 people unemployed due to its closure.

## Retirement

Due to its effects, the name Lenny was retired by the World Meteorological Organization in the spring of 2000, and will never again be used for an Atlantic hurricane. The name was replaced with Lee in the 2005 season.

## See also

- List of Category 4 Atlantic hurricanes
- List of South America hurricanes
- Timeline of the 1999 Atlantic hurricane season
- Hurricane Klaus (1984) – A Category 1 hurricane that impacted similar areas
- Hurricane Omar (2008) – A Category 4 hurricane that impacted similar areas
- Hurricane Paloma (2008) – Another intense Category 4 November hurricane that struck Cuba

Category 4 Atlantic hurricane in 1999

1999 in the United States Virgin Islands

Hurricanes in the British Virgin Islands

Hurricanes in the United States Virgin Islands


Β-Hydroxy β-methylbutyric acid

β-Hydroxy β-methylbutyric acid (HMB), otherwise known as its conjugate base, β-hydroxy β-methylbutyrate, is a naturally produced substance in humans that is used as a dietary supplement and as an ingredient in certain medical foods that are intended to promote wound healing and provide nutritional support for people with muscle wasting due to cancer or HIV/AIDS. In healthy adults, supplementation with HMB has been shown to increase exercise-induced gains in muscle size, muscle strength, and lean body mass, reduce skeletal muscle damage from exercise, improve aerobic exercise performance, and expedite recovery from exercise. Medical reviews and meta-analyses indicate that HMB supplementation also helps to preserve or increase lean body mass and muscle strength in individuals experiencing age-related muscle loss. HMB produces these effects in part by stimulating the production of proteins and inhibiting the breakdown of proteins in muscle tissue. No adverse effects from long-term use as a dietary supplement in adults have been found.

HMB is sold as a dietary supplement at a cost of about –50 per month when taking 3 grams per day. HMB is also contained in several nutritional products, including certain formulations of Ensure and Juven. HMB is also present in insignificant quantities in certain foods, such as alfalfa, asparagus, avocados, cauliflower, grapefruit, and catfish.

The effects of HMB on human skeletal muscle were first discovered by Steven L. Nissen at Iowa State University in the mid-1990s. As of 2018, HMB has not been banned by the National Collegiate Athletic Association, World Anti-Doping Agency, or any other prominent national or international athletic organization. In 2006, only about 2% of college student athletes in the United States used HMB as a dietary supplement. As of 2017, HMB has found widespread use as an ergogenic supplement among young athletes.

## Uses

### Available forms

HMB is sold as an over-the-counter dietary supplement in the free acid form, β-hydroxy β-methylbutyric acid (HMB-FA), and as a monohydrated calcium salt of the conjugate base, calcium β-hydroxy β-methylbutyrate monohydrate (HMB-Ca, CaHMB). Since only a small fraction of HMB's metabolic precursor, -leucine, is metabolized into HMB, pharmacologically active concentrations of the compound in blood plasma and muscle can only be achieved by supplementing HMB directly. A healthy adult produces approximately 0.3 grams per day, while supplemental HMB is usually taken in doses of 3–6 grams per day. HMB is sold at a cost of about –50 per month when taken in doses of 3 grams per day. HMB is also contained in several nutritional products and medical foods marketed by Abbott Laboratories (e.g., certain formulations of Ensure and Juven), and is present in insignificant quantities in certain foods, such as alfalfa, asparagus, avocados, cauliflower, grapefruit, and catfish.

### Medical

Supplemental HMB has been used in clinical trials as a treatment for preserving lean body mass in muscle wasting conditions, particularly sarcopenia, and has been studied in clinical trials as an adjunct therapy in conjunction with resistance exercise. Based upon two medical reviews and a meta-analysis of seven randomized controlled trials, HMB supplementation can preserve or increase lean muscle mass and muscle strength in sarcopenic older adults. HMB does not appear to significantly affect fat mass in older adults. Preliminary clinical evidence suggests that HMB supplementation may also prevent muscle atrophy during bed rest. A growing body of evidence supports the efficacy of HMB in nutritional support for reducing, or even reversing, the loss of muscle mass, muscle function, and muscle strength that occurs in hypercatabolic disease states such as cancer cachexia; consequently, the authors of two 2016 reviews of the clinical evidence recommended that the prevention and treatment of sarcopenia and muscle wasting in general include supplementation with HMB, regular resistance exercise, and consumption of a high-protein diet.

Clinical trials that used HMB for the treatment of muscle wasting have involved the administration of 3 grams of HMB per day under different dosing regimens. According to one review, an optimal dosing regimen is to administer it in one 1 gram dose, three times a day, since this ensures elevated plasma concentrations of HMB throughout the day; however, as of 2016 the best dosing regimen for muscle wasting conditions is still being investigated.

Some branded products that contain HMB (i.e., certain formulations of Ensure and Juven) are medical foods that are intended to be used to provide nutritional support under the care of a doctor in individuals with muscle wasting due to HIV/AIDS or cancer, to promote wound healing following surgery or injury, or when otherwise recommended by a medical professional. Juven, a nutrition product which contains 3 grams of HMB-Ca, 14 grams of -arginine, and 14 grams of -glutamine per two servings, has been shown to improve lean body mass during clinical trials in individuals with AIDS and cancer, but not rheumatoid cachexia. Further research involving the treatment of cancer cachexia with Juven over a period of several months is required to adequately determine treatment efficacy.

### Enhancing performance

With an appropriate exercise program, dietary supplementation with 3 grams of HMB per day has been shown to increase exercise-induced gains in muscle size, muscle strength and power, and lean body mass, reduce exercise-induced skeletal muscle damage, and expedite recovery from high-intensity exercise. Based upon limited clinical research, HMB supplementation may also improve aerobic exercise performance and increase gains in aerobic fitness when combined with high-intensity interval training. These effects of HMB are more pronounced in untrained individuals and athletes who perform high intensity resistance or aerobic exercise. In resistance-trained populations, the effects of HMB on muscle strength and lean body mass are limited. HMB affects muscle size, strength, mass, power, and recovery in part by stimulating myofibrillar muscle protein synthesis and inhibiting muscle protein breakdown through various mechanisms, including the activation of mechanistic target of rapamycin complex 1 (mTORC1) and inhibition of proteasome-mediated proteolysis in skeletal muscles.

The efficacy of HMB supplementation for reducing skeletal muscle damage from prolonged or high-intensity exercise is affected by the time that it is used relative to exercise. The greatest reduction in skeletal muscle damage from a single bout of exercise has been shown to occur when HMB-Ca is ingested 1–2 hours prior to exercise or HMB-FA is ingested 30–60 minutes prior to exercise.

In 2006, only about 2% of college student athletes in the United States used HMB as a dietary supplement. As of 2017, HMB has found widespread use as an ergogenic supplement among athletes. As of 2018, HMB has not been banned by the National Collegiate Athletic Association, World Anti-Doping Agency, or any other prominent national or international athletic organization.

## Side effects

The safety profile of HMB in adult humans is based upon evidence from clinical trials in humans and animal studies. In humans, no adverse effects in young adults or older adults have been reported when HMB is taken in doses of 3 grams per day for up to a year. Studies on young adults taking 6 grams of HMB per day for up to 2 months have also reported no adverse effects. Studies with supplemental HMB on young, growing rats and livestock have reported no adverse effects based upon clinical chemistry or observable characteristics; for humans younger than 18, there is limited data on the safety of supplemental HMB. The human equivalent dose of HMB for the no-observed-adverse-effect level (NOAEL) that was identified in a rat model is approximately 0.4 g/kg of body weight per day.

Two animal studies have examined the effects of HMB supplementation in pregnant pigs on the offspring and reported no adverse effects on the fetus. No clinical testing with supplemental HMB has been conducted on pregnant women, and pregnant and lactating women are advised not to take HMB by Metabolic Technologies, Inc., the company that grants licenses to include HMB in dietary supplements, due to a lack of safety studies.

## Pharmacology

### Pharmacodynamics

Several components of the signaling cascade that mediates the HMB-induced increase in human skeletal muscle protein synthesis have been identified in vivo. Similar to HMB's metabolic precursor, -leucine, HMB has been shown to increase protein synthesis in human skeletal muscle via phosphorylation of the mechanistic target of rapamycin (mTOR) and subsequent activation of , which leads to protein biosynthesis in cellular ribosomes via phosphorylation of mTORC1's immediate targets (i.e., the p70S6 kinase and the translation repressor protein 4EBP1). Supplementation with HMB in several non-human animal species has been shown to increase the serum concentration of growth hormone and insulin-like growth factor 1 (IGF-1) via an unknown mechanism, in turn promoting protein synthesis through increased mTOR phosphorylation. Based upon limited clinical evidence in humans, supplemental HMB appears to increase the secretion of growth hormone and IGF-1 in response to resistance exercise.

As of 2016, the signaling cascade that mediates the HMB-induced reduction in muscle protein breakdown has not been identified in living humans, although it is well-established that it attenuates proteolysis in humans in vivo. Unlike -leucine, HMB attenuates muscle protein breakdown in an insulin-independent manner in humans. HMB is believed to reduce muscle protein breakdown in humans by inhibiting the 19S and 20S subunits of the ubiquitin–proteasome system in skeletal muscle and by inhibiting apoptosis of skeletal muscle nuclei via unidentified mechanisms.

Based upon animal studies, HMB appears to be metabolized within skeletal muscle into cholesterol, which may then be incorporated into the muscle cell membrane, thereby enhancing membrane integrity and function. The effects of HMB on muscle protein metabolism may help stabilize muscle cell structure. One review suggested that the observed HMB-induced reduction in the plasma concentration of muscle damage biomarkers (i.e., muscle enzymes such as creatine kinase and lactate dehydrogenase) in humans following intense exercise may be due to a cholesterol-mediated improvement in muscle cell membrane function.

HMB has been shown to stimulate the proliferation, differentiation, and fusion of human myosatellite cells in vitro, which potentially increases the regenerative capacity of skeletal muscle, by increasing the protein expression of certain myogenic regulatory factors (e.g., myoD and myogenin) and gene transcription factors (e.g., MEF2). HMB-induced human myosatellite cell proliferation in vitro is mediated through the phosphorylation of the mitogen-activated protein kinases ERK1 and ERK2. HMB-induced human myosatellite differentiation and accelerated fusion of myosatellite cells into muscle tissue in vitro is mediated through the phosphorylation of Akt, a serine/threonine-specific protein kinase.

### Pharmacokinetics

#### Comparison of pharmacokinetics between dosage forms

The free acid (HMB-FA) and monohydrated calcium salt (HMB-Ca) forms of HMB have different pharmacokinetics. HMB-FA is more readily absorbed into the bloodstream and has a longer elimination half-life (3 hours) relative to HMB-Ca (2.5 hours). Tissue uptake and utilization of HMB-FA is 25–40% higher than for HMB-Ca. The fraction of an ingested dose that is excreted in urine does not differ between the two forms.

#### Absorption of HMB-Ca

After ingestion, HMB-Ca is converted to β-hydroxy β-methylbutyrate following dissociation of the calcium moiety in the gut. When the HMB-Ca dosage form is ingested, the magnitude and time at which the peak plasma concentration of HMB occurs depends on the dose and concurrent food intake. Higher HMB-Ca doses increase the rate of absorption, resulting in a peak plasma HMB level (Cmax) that is disproportionately greater than expected of a linear dose-response relationship and which occurs sooner relative to lower doses. Consumption of HMB-Ca with sugary substances slows the rate of HMB absorption, resulting in a lower peak plasma HMB level that occurs later.

#### Excretion of HMB-Ca

HMB is eliminated via the kidneys, with roughly 10–40% of an ingested dose being excreted unchanged in urine. The remaining 60–90% of the dose is retained in tissues or excreted as HMB metabolites. The fraction of a given dose of HMB that is excreted unchanged in urine increases with the dose.

#### Metabolism

The metabolism of HMB is catalyzed by an uncharacterized enzyme which converts it to β-hydroxy β-methylbutyryl-CoA (HMB-CoA). HMB-CoA is metabolized by either enoyl-CoA hydratase or another uncharacterized enzyme, producing β-methylcrotonyl-CoA (MC-CoA) or hydroxymethylglutaryl-CoA (HMG-CoA) respectively. MC-CoA is then converted by the enzyme methylcrotonyl-CoA carboxylase to methylglutaconyl-CoA (MG-CoA), which is subsequently converted to HMG-CoA by methylglutaconyl-CoA hydratase. HMG-CoA is then cleaved into acetyl-CoA and acetoacetate by HMG-CoA lyase or used in the production of cholesterol via the mevalonate pathway.

### Biosynthesis

HMB is synthesized in the human body through the metabolism of -leucine, a branched-chain amino acid. In healthy individuals, approximately 60% of dietary -leucine is metabolized after several hours, with roughly 5% (2–10% range) of dietary -leucine being converted to .

The vast majority of -leucine metabolism is initially catalyzed by the branched-chain amino acid aminotransferase enzyme, producing α-ketoisocaproate (α-KIC). α-KIC is mostly metabolized by the mitochondrial enzyme branched-chain α-ketoacid dehydrogenase, which converts it to isovaleryl-CoA. Isovaleryl-CoA is subsequently metabolized by isovaleryl-CoA dehydrogenase and converted to MC-CoA, which is used in the synthesis of acetyl-CoA and other compounds. During biotin deficiency, HMB can be synthesized from MC-CoA via enoyl-CoA hydratase and an unknown thioesterase enzyme, which convert MC-CoA into HMB-CoA and HMB-CoA into HMB respectively. A relatively small amount of α-KIC is metabolized in the liver by the cytosolic enzyme 4-hydroxyphenylpyruvate dioxygenase (KIC dioxygenase), which converts α-KIC to HMB. In healthy individuals, this minor pathway – which involves the conversion of -leucine to α-KIC and then HMB – is the predominant route of HMB synthesis.

## Chemistry

β-Hydroxy β-methylbutyric acid is a monocarboxylic β-hydroxy acid and natural product with the molecular formula C5H10O3. At room temperature, pure β-hydroxy β-methylbutyric acid occurs as a transparent, colorless to light yellow liquid which is soluble in water. β-Hydroxy β-methylbutyric acid is a weak acid with a pKa of 4.4. Its refractive index ($\mathit{n}_\text{25°C}^\mathrm{\lambda=589nm}$) is 1.42.

### Chemical structure

β-Hydroxy β-methylbutyric acid is a member of the carboxylic acid family of organic compounds. It is a structural analog of butyric acid with a hydroxyl functional group and a methyl substituent located on its beta carbon. By extension, other structural analogs include β-hydroxybutyric acid and β-methylbutyric acid.

### Synthesis

A variety of synthetic routes to β-hydroxy β-methylbutyric acid have been developed. The first reported chemical syntheses approached HMB by oxidation of alkene, vicinal diol, and alcohol precursors:

- in 1877, Russian chemists Michael and Alexander Zaytsev reported the preparation of HMB by oxidation of 2-methylpent-4-en-2-ol with chromic acid (H2CrO4);
- in 1880 and 1889, Schirokoff and Reformatsky (respectively) reported that the oxidative cleavage of the vicinal diol 4-methylpentane-1,2,4-triol with acidified potassium permanganate (KMnO4) yields HMB – this result is closest related to the first synthesis as cold dilute KMnO4 oxidises alkenes to vicinal cis-diols which hot acid KMnO4 further oxidises to carbonyl-containing compounds, and the diol intermediate is not obtained when hot acidic conditions are used for alkene oxidation. In other words, racemic 4-methylpentane-1,2,4-triol is a derivative of 2-methylpent-4-en-2-ol and β-hydroxy β-methylbutyric acid is a derivative of both; and,
- in 1892, Kondakow reported the preparation of HMB by permanganate oxidation of 3-methylbutane-1,3-diol.

Depending on the experimental conditions, cycloaddition of acetone and ketene produces either β-isovalerolactone or 4,4-dimethyloxetan-2-one, both of which hydrolyze under basic conditions to yield the conjugate base of HMB. The haloform reaction provides another pathway to HMB involving the exhaustive halogenation of the methyl-ketone region of diacetone alcohol with sodium hypobromite or sodium hypochlorite; Diacetone alcohol is readily available from the aldol condensation of acetone. An organometallic approach to HMB involves the carboxylation of tert-butyl alcohol with carbon monoxide and Fenton's reagent (hydrogen peroxide and ferrous iron). Alternatively, HMB can be prepared through microbial oxidation of β-methylbutyric acid by the fungus Galactomyces reessii.

### Detection in body fluids

The concentration of naturally produced HMB has been measured in several human body fluids using nuclear magnetic resonance spectroscopy, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry methods. In the blood plasma and cerebrospinal fluid (CSF) of healthy adults, the average molar concentration of HMB has been measured at 4.0 micromolar (μM). The average concentration of HMB in the intramuscular fluid of healthy men of ages 21–23 has been measured at 7.0 μM. In the urine of healthy individuals of any age, the excreted urinary concentration of HMB has been measured in a range of 0–68 micromoles per millimole (μmol/mmol) of creatinine. In the breast milk of healthy lactating women, HMB and -leucine have been measured in ranges of 42–164 μg/L and 2.1–88.5 mg/L. In comparison, HMB has been detected and measured in the milk of healthy cows at a concentration of \<20–29 μg/L. This concentration is far too low to be an adequate dietary source of HMB for obtaining pharmacologically active concentrations of the compound in blood plasma.

In a study where participants consumed 2.42 grams of pure HMB-FA while fasting, the average plasma HMB concentration increased from a basal level of 5.1 μM to 408 μM after 30 minutes. At 150 minutes post-ingestion, the average plasma HMB concentration among participants was 275 μM.

Abnormal HMB concentrations in urine and blood plasma have been noted in several disease states where it may serve as a diagnostic biomarker, particularly in the case of metabolic disorders. The following table lists some of these disorders along with the associated HMB concentrations detected in urine or blood plasma.

## History

The first reported chemical synthesis of HMB was published in 1877 by the Russian chemists Michael and Alexander Zaytsev. HMB was isolated from the bark of Erythrophleum couminga (a Madagascan tree) in 1941 by Leopold Ružička. The earliest reported isolation of HMB as a human metabolite was by Tanaka and coworkers in 1968 from a patient with isovaleric acidemia.

The effects of HMB on human skeletal muscle were first discovered by Steven L. Nissen at Iowa State University in the mid-1990s. Nissen founded a company called Metabolic Technologies, Inc. (MTI) around the time of his discovery, which later acquired six HMB-related patents that the company has used to license the right to manufacture and incorporate HMB into dietary supplements. When it first became available commercially in the late 1990s, HMB was marketed solely as an exercise supplement to help athletes and bodybuilders build muscle. MTI subsequently developed two HMB-containing products, Juven and Revigor, to which Abbott Nutrition obtained the market rights in 2003 and 2008 respectively. Since then, Abbott has marketed Juven as a medical food and the Revigor brand of HMB as an active ingredient in food products (e.g., certain formulations of Ensure) and other medical foods (e.g., certain formulations of Juven).

## See also

- 3-Aminoisobutyric acid

## Reference notes

Chemical compound