Cytoprotective properties of melatonin: presumed association with oxidative damage and aging

For years melatonin, a molecule widely produced in both the plant and animal kingdom, was thought to function exclusively as a synchronizer of seasonal reproduction, adjuster of the biological clock, sleep-inducing agent, and immune system stimulator. More recently melatonin has also been found to be a free-radical scavenger and antioxidant. Although pharmacologic levels (higher than those normally present endogenously) of melatonin possess substantial protective activity against molecular damage inflicted by free radicals, its role as a physiologic antioxidant is currently under active investigation. Toxic free radicals have been implicated in a variety of age-associated degenerative diseases, as well as in aging itself. Because melatonin production falls substantially during aging, the loss of this antioxidant is theorized to be instrumental in the degenerative processes associated with advanced age. The exogenous administration of melatonin has been found to be effective in reducing macromolecular damage that is normally seen in experimental models of age-related diseases. How effective melatonin will be in terms of deferring aging, however, must await the outcome on subsequent studies.