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Melatonin is a hormone produced in the brain by the pineal gland from the amino acid tryptophan. The synthesis and release of melatonin are stimulated by darkness and suppressed by light, suggesting the involvement of melatonin in circadian rhythm and regulation of diverse body functions. Levels of melatonin in the blood are highest prior to bedtime. Synthetic melatonin supplements have been used for a variety of medical conditions, most notably for disorders related to sleep. Melatonin possesses antioxidant activity, and many of its proposed therapeutic or preventive uses are based on this property. New drugs that block the effects of melatonin are in development, such as BMS-214778 or luzindole, and may have uses in various disorders.
The term ginseng refers to several species of the genus Panax . For more than 2,000 years, the roots of this slow-growing plant have been valued in Chinese medicine. The two most commonly used species are Asian ginseng ( Panax ginseng C. A. Meyer), which is almost extinct in its natural habitat but is still cultivated, and American ginseng ( P . quinquefolius L.), which is both harvested from the wild and cultivated. Panax ginseng should not be confused with Siberian ginseng ( Eleutherococcus senticosus ). In Russia, Siberian ginseng was promoted as a cheaper alternative to ginseng and was believed to have identical benefits. However, Siberian ginseng does not contain the ginsenosides found in the Panax species, which are believed to be active ingredients and have been studied.
Evening primrose oil (EPO) contains an omega-6 essential fatty acid, gamma-linolenic acid (GLA), which is believed to be the active ingredient. EPO has been studied in a wide variety of disorders, particularly those affected by metabolic products of essential fatty acids. However, high-quality evidence for its use in most conditions is still lacking.