Title:The Universal Nature, Unequal Distribution and Antioxidant Functions of Melatonin and Its Derivatives
VOLUME: 13 ISSUE: 3
Author(s):Russel J. Reiter, Dun-Xian Tan, Sergio Rosales-Corral and Lucien C. Manchester
Affiliation:Department of Cellular and Structural Biology, UT Health Science Center, San Antonio, Texas, USA.
Keywords:Animals, plants, intracellular concentrations, melatonin, free radicals, oxidative stress
Abstract:Melatonin is an uncommonly widely distributed molecule. It is found throughout the plant and animal
kingdoms, i.e., perhaps in every living organism. Within vertebrate organisms, melatonin also has an extremely wide
distribution, seemingly being capable of entering every cell and all subcellular compartments. So-called morphophysiological
barriers, e.g., the blood-brain barrier, are no impediment to the passage of melatonin and it has a multitude of confirmed
functions. We have hypothesized that melatonin originally evolved as a free radical scavenger and during evolution it
acquired other important and essential actions. Due to the multi-faceted actions of melatonin and its metabolites as direct
free radical scavengers and indirect antioxidants, these agents have been used to abate oxidative damage in a diverse
variety of experimental models where free radical destruction is a component. When compared with classic, better-known
antioxidants, melatonin is better in terms of limiting destruction of intracellular macromolecules when the damage is a
consequence of excessive oxygen or nitrogen-based toxic reactants. Considering the vast array of experimental data that
has accumulated which documents melatonin’s high efficacy and lack of, or minimal, toxicity over a very wide dose
range, it is essential that the usefulness of this agent be more thoroughly tested at the clinical level. The findings from
experimental models of numerous diseases overwhelming confirm that this indoleamine would likely have great benefit in
aiding humans suffering with conditions that have as their basis tissue and molecular damage resulting from oxygen and
nitrogen-based reactants.
