查看文章

This survey summarizes the findings, accumulated within the last 2 years, concerning melatonin's role in defending against toxic free radicals. Free radicals are chemical constituents that have an unpaired electron in their outer or‐bital and, because of this feature, are highly reactive. Inspired oxygen, which sustains life, also is harmful because up to 5% of the oxygen (O₂) taken in is converted to oxygen‐free radicals. The addition of a single electron to O₂ produces the superoxide anion radical (O₂); C₂: is catalytic‐reduced by superoxide dismutase, to hydrogen peroxide (H₂O₂). Although H₂O₂ is not itself a free radical, it can be toxic at high concentrations and, more importantly, it can be reduced to the hydroxyl radical (OH). The OH is the most toxic of the oxygen‐based radicals and it wreaks havoc within cells, particularly with macromolecules. In recent in vitro studies, melatonin was shown to be a very efficient …