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Melatonin (Molecule of the Month for June 2016)

biological clock

Melatonin is a hormone found in all living creatures. It is naturally synthesized from the amino acid tryptophan, via synthesis of serotonin, by the enzyme 5-hydroxyindole-O-methyltransferase. Nobel Prize laureate Julius Axelrod performed many of the seminal experiments that elucidated the role of melatonin and the pineal gland in regulating sleep-wake cycles (circadian rhythms). In humans, melatonin is produced by the pineal gland, a gland about the size of a pea, that is located in the center of the brain. Normally, the production of melatonin by the pineal gland is inhibited by light and permitted by darkness. For this reason melatonin has been called "the hormone of darkness". The secretion of melatonin peaks in the middle of the night, and gradually falls during the second half of the night. Until recent history, humans in temperate climates were exposed to up to eighteen hours of darkness in the winter. In this modern world, artificial lighting typically reduces this to eight hours or less per day all year round.

In animal models, melatonin has been demonstrated to prevent the damage to DNA by some carcinogens, stopping the mechanism by which they cause cancer. The antioxidant activity of melatonin may reduce damage caused by some types of Parkinson's disease, may play a role in preventing cardiac arrhythmia and may increase longevity; it has been shown to increase the average life span of mice by 20% in some studies.

Melatonin appears to have some use against circadian rhythm sleep disorders, such as jet lag and delayed sleep phase syndrome. The primary motivation for the use of melatonin as a supplement is as a natural aid to better sleep, with other incidental benefits to health and well-being due to its role as an antioxidant and its stimulation of the immune system and several components of the endocrine system.

Formal Chemical Name (IUPAC)



Picture of Melatonin

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Melatonin structure
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Picture of Melatonin


Update by Karl Harrison
(Molecule of the Month for June 2016 )