Melatonin: Helping cells cope with oxidative disaster
Sergio Damian Paredes Royano, RusseL J Reiter
Melatonin possesses the capability of donating electrons, consequently reducing the reactivity of molecules with an unpaired electron in their valence orbital, i.e. free radicals. A plethora of studies support the role of this indoleamine in diminishing molecular damage associated with massive free radical generation both in vitro and in vivo. Melatonin protects against neurodegenerative disorders, ischemia/reperfusion injury, acts as a radio protector, and counteracts herbicide and metal toxicity due to its essential role in antioxidant protection. At the intracellular level, it reduces electron leakage from the mitochondrial respiratory chain complexes as well as scavenging radicals generated in the cytosol (exclusive of its actions in mitochondria) and nucleus. Comparative studies with other well-known naturally occurring antioxidants show that melatonin’s efficacy is equal to or better in neutralizing highly toxic oxygen and nitrogen-reactants. However, not only melatonin but a series of its metabolites are also capable of detoxifying free radicals and related species in what is referred to as the antioxidative cascade. Thus, melatonin may be actually seen as a prodrug for a family of other molecules that also have the capability of reducing oxidative/nitrosative stress. Taken together, the results reviewed here indicate that melatonin is a key element in antioxidative medicine in the context of the antioxidative defense system.
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