Melatonin
This is an ACS Molecule of the Week (7-11-11)
"Melatonin, or N-acetyl-5-methoxytryptamine, is a hormone that is secreted by the pineal gland in mammals; it is also found in other animals, plants, and microorganisms. It helps regulate the circadian rhythms of biological functions. A. B. Lerner and co-workers isolated melatonin from cattle pineal glands in 1958 and characterized it a year later. The following year, J. Szmuszkovicz et al. published two laboratory syntheses of melatonin."