The beta-carotene is firstly cleaved into beta-carotene 15-15-monooxygenase through site 1 double bond oxidized to epoxide. The epoxide is attacked by water to form diol in site 1. NADH, as a reduction agent, reduce the alcohol group to aldehydes. History
Tretinoin was co-developed for its use in acne by James Fulton and Albert Kligman when they were at University of Pennsylvania in the 1960s. Phase I trials, the first conducted on human subjects, were performed on inmates at Holmesburg Prison during a long-running regime of non-therapeutic and unethical testing on prison inmates at Holmesburg. The University of Pennsylvania held the patent for Retin-A, which it licensed to pharmaceutical companies.Treatment of acute promyelocytic leukemia was first introduced at Ruijin Hospital in Shanghai by Wang Zhenyi in a 1988 clinical trial. Etymology
The origin of the name tretinoin is uncertain, although several sources agree (one with probability, one with asserted certainty) that it probably comes from trans- + retinoic [acid] + -in, which is plausible given that tretinoin is the all-trans isomer of retinoic acid. The name isotretinoin is the same root tretinoin plus the prefix iso-. Regarding pronunciation, the following variants apply equally to both tretinoin and isotretinoin. Given that retinoic is pronounced , it is natural that  is a commonly heard pronunciation. Dictionary transcriptions also include  (tri-TIN-oh-in) and .
Research
Tretinoin has been explored as a treatment for hair loss, potentially as a way to increase the ability of minoxidil to penetrate the scalp, but the evidence is weak and contradictory.It has been used off-label to treat and reduce the appearance of stretch marks. It has also been studied in skin aging. References
External links
"Tretinoin". Drug Information Portal. U.S. National Library of Medicine. "Tretinoin Topical". MedlinePlus.