Sweetgrass, a plant used in traditional medicine, contains compounds that can repel mosquitoes. 
 
 To keep mosquitoes at bay, all it may take is a bit of planting. 
 
 New research finds that sweetgrass, a meadow grass native to northern climates, contains chemicals that work as well as DEET in fending off the blood-sucking insects. 
 
 Charles Cantrell and his team at the U.S. Department of Agriculture, in collaboration with researchers at the University of Guelph and the University of Mississippi, put the plant’s oil to the test. 
 
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 First they extracted the oil from the sweetgrass using steam distillation. Then they filled vials of a red-colored, human blood-like solution and covered the vials with thin membranes – mimicking human skin. Each vial’s membrane was coated with one of three substances — the sweetgrass oil, sweetgrass extracts taken without steam distillation, DEET, and a control of ethanol. 
 
 Then they offered up the vials to the mosquitoes — and counted how many mosquitoes went for each vial. 
 
 “Then you take the mosquitoes and squish them on some paper,” Cantrell explained in a press release. “If they have the blood mimic in them, you see it right there on the paper.” 
 
 The final tally showed that the vials coated with steam distilled sweetgrass oil and the ones coated in DEET worked best and got the fewest bites. 
 
 But what chemicals in the oil was fending off the mosquitoes? To test that, Cantrell and his team purified the oil into 12 fractions and checked each part’s ability to ward off the bugs. 
 
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 They identified two key chemicals present in the three most effective vials — phytol and coumarin. Coumarin is a chemical already used in some bug repellents and phytol has already been cited as an effective repellent in scientific literature. 
 
 So while the sweetgrass chemicals had already been identified as effective mosquito repellents, now there’s proof that nature packs its own natural bug repellent in the natural aroma of sweetgrass. 
 
 The research is being presented at a meeting this week of the American Chemical Society in Boston. 

 BOSTON, Aug. 17, 2015 --Native North Americans have long adorned themselves and their homes with fragrant sweetgrass (Hierochloe odorata), a native plant used in traditional medicine, to repel biting insects, and mosquitoes in particular. Now, researchers report that they have identified the compounds in sweetgrass that keep these bugs at bay. 
 
 The team will describe their approach in one of more than 9,000 presentations at the 250th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society, taking place here through Thursday. 
 
 Mosquitoes and other insects remain a pesky part of everyday life in many parts of the world, and their bites are linked to a range of serious diseases, such as malaria. To add to the arsenal of insect repellents, Charles Cantrell, Ph.D., investigates the components of plants used in traditional therapies. "We found that in our search for new insect repellents, folk remedies have provided good leads." 
 
 Sweetgrass is a meadow grass that is a native to northern climates, Cantrell says. "It gives off a sweet aroma that repels mosquitoes." 
 
 He therefore suspected that the active insect-repelling chemicals must waft off sweetgrass at ambient temperatures and, like essential oils from lavender and other plants, could be extracted using a process known as steam distillation. This method involves passing hot steam through plant material, then lowering the temperature. The condensed liquid then separates into oil and water, with the oil fraction containing the volatile chemicals of interest. So, Cantrell's team at the U.S. Department of Agriculture, in collaboration with researchers at the University of Guelph and the University of Mississippi, performed steam distillation on sweetgrass samples and evaluated its oil for the ability to deter mosquitoes from biting. 
 
 To test the mosquitoes' aversion to the oil, the researchers filled small vials with a red-colored feeding solution that mimicked human blood and covered the vials with a thin membrane. Then, they coated the membranes with different substances: the sweetgrass oil, alternative sweetgrass extracts obtained without steam distillation, the gold-standard insect repellent N,N-diethyl-m-toluamide (DEET) or the ethanol solvent control. Then, the bugs got the chance to either bite the membranes to get to the blood or pass them by. The researchers observed what the insects did, counting how many mosquitoes went for a bite of each type of "blood" vat. 
 
 "Then you take the mosquitoes and squish them on some paper," says Cantrell. "If they have the blood mimic in them, you see it right there on the paper." Of the sweetgrass extracts, the steam-distilled oil got the fewest mosquito bites, matching the repellent potency of DEET. 
 
 The next step was to figure out the exact chemicals that give the sweetgrass oil its anti-mosquito power. The researchers purified the oil into 12 fractions and again checked their ability to ward off the bugs. They found three fractions that repelled mosquitoes as well as the oil. Using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry, the researchers identified two chemicals in these active fractions that seemed to be responsible for putting off mosquitoes: phytol and coumarin. 
 
 Coumarin is an ingredient in some commercial anti-mosquito products, he adds, while phytol is reported to have repelling activity in the scientific literature. So although Cantrell didn't find brand-new insect deterrents in this experiment, he is happy to have demonstrated that "we were able to find constituents that are known to act as insect repellents in a folk remedy, and now we understand that there's a real scientific basis to this folklore." 
 
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 A press conference on this topic will be held Tuesday, Aug. 18, at 10:30 a.m. Eastern time in the Boston Convention & Exhibition Center. Reporters may check-in at Room 153B in person, or watch live on YouTube http://bit. ly/ ACSLiveBoston . To ask questions online, sign in with a Google account. 
 
 Cantrell acknowledges that the study was supported in part by a Deployed War-Fighter Protection research program grant funded by the U.S. Department of Defense through the Armed Forces Pest Management Board. 
 
 The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 158,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio. 
 
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 Note to journalists: Please report that this research is being presented at a meeting of the American Chemical Society. 
 
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 Title 
 
 Isolation and Identification of Potential Biopesticidal Compounds from the North American Insect Repelling Folk Remedy Plant, Sweetgrass, Hierochloe odorata (L.) P. Beauv. 
 
 Abstract 
 
 Native North Americans used sweetgrass, Hierochloe odorata, in a variety of ceremonies and rituals. It has also been used to repel biting insects by making a loop from strands of the grass to be worn around the neck or kept in a satchel hung in homes. This investigation was conducted to evaluate this practice and systematically identify chemical constituents responsible for the mosquito repelling effect by utilizing a mosquito (Aedes aegypti) biting deterrent bioactivity-directed purification approach. Fresh steam distilled oil was found to be the most active crude extract generated from sweetgrass and was used in fractionation studies providing 12 distinct fractions. Fractions identified as having activity equivalent to N,N-diethyl-m-toluamide (DEET) contained the compounds phytol and coumarin. Ae. aegypti biting deterrent results will be reported for the active fraction and pure compounds.
– Native North Americans have long used the fragrant herb sweetgrass to ward off biting insects like mosquitoes, and new research shows how the traditional repellent works chemically. About to share their findings with the American Chemical Society, researchers at the US Department of Agriculture, the University of Guelph, and the University of Mississippi report in a press release that sweetgrass contains two chemicals, phytol and coumarin, that appear to be responsible. "Traditional or folk remedies have been a good source of leads for natural things that may be effective in repelling insects," says Charles Cantrell, who works at the USDA's Natural Products Utilization Research Unit; he's also studied breadfruit, beautyberry, and Jatropha, reports the Smithsonian. Unfortunately, many essential oil repellents only work for 20 or so minutes, he says, and "what we're ideally looking for is something natural and nontoxic that's just as effective as DEET, that will work as an effective repellent for 10 or 12 hours like DEET." Sweetgrass is a meadow grass native to northern climates, reports Discovery. Cantrell's team needs to study the chemicals phytol and coumarin further to see if they will be effective for as long as DEET is, and while sweetgrass didn't turn out to have any previously unknown repelling chemicals (coumarin is already in some commercial repellents while phytol has already been reported on in other studies), at least "now we understand that there's a real scientific basis to this folklore," Cantrell says. (Lemon eucalyptus and black pepper plants may also rival DEET.)