Oxidation of melatonin by taurine chloramine.

Melatonin is widely known for its antioxidant, immunomodulatory, and anti-inflammatory effects. Hypochlorous acid (HOCl) is one example of an endogenous oxidant that is promptly neutralized by melatonin. Melatonin also inhibits myeloperoxidase, the enzyme that catalyzes the oxidation of chloride to HOCl.

Oxidation of melatonin by AAPH-derived peroxyl radicals: evidence of a pro-oxidant effect of melatonin.

Background: Melatonin is well-established as a powerful reducing agent of oxidant generated in the cell medium. We aimed to investigate how readily melatonin is oxidized by peroxyl radicals ROO generated by the thermolysis of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) and the role of glutathione (GSH) during the reaction course.

Methods: Chromatographic, mass spectroscopy, and UV-visible spectrometric techniques were used to study the oxidation of melatonin by ROO or horseradish peroxidase (HRP)/H2O2.