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From Biology-Online Dictionary | Biology-Online Dictionary
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noun, plural: melatonin or melatonins

The hormone involved in the regulation of several physiological mechanisms in living things, such as circadian rhythm in animals, colour changes in the skin of reptiles, reproductive cycles in mammals, and defense against oxidative stress in plants


Melatonin is associated with the regulation of circadian rhythm, colour changes in the skin of reptiles, and reproductive cycles in mammals. As regards circadian rhythm, it is involved in sleep-wake timing, blood pressure regulation, seasonal reproduction, etc. Melatonin is also produced in plants where it is involved in defending plants from oxidative stress.

In humans and other vertebrates, the melatonin is a hormone produced and secreted by the pineal gland. The pineal gland is comprised mainly of pinealocytes, which are the cells that produce melatonin. The secretion of melatonin is regulated by norepinephrine. Melatonin is produced usually at night (darkness). The duration of melatonin production is affected by the differing duration of nighttime. This consequently serves as a signal for photoperiodic biological functions such as mentioned above.

In plants, the melatonin is an efficient protector against stress. In the event of a stress, such as fungal infection and temperature extremes, there is a heightened production of melatonin in plants. It actively scavenges free radicals in plants and can activate antioxidant enzymes. Apart from this, it is also involved in regulating plant growth.

IUPAC name:

  • N-[2-(5-Methoxy-1H-indol-3-yl)ethyl]acetamide

Chemical formula:

  • C13H16N2O2

Also called: N-acetyl-5-methoxy tryptamine See also: