Melatonin

Melatonin is an indoleamine neurohormone whose levels vary in a daily cycle, thereby allowing the entrainment of the circadian rhythms of several biological functions in animals, plants, and microbes. Many biological effects of melatonin are transduced through melatonin receptors, including the MT1, MT2, and MT3 subtypes. Glutathione peroxidase, superoxide dismutases, and catalase are upregulated by melatonin.