The reaction of melatonin with peroxynitrite: formation of melatonin radical cation and absence of stable nitrated products.
Peroxynitrite is capable of hydroxylating and nitrating aromatic species. However, nitromelatonin is not found as a final product when melatonin was allowed to react with peroxynitrite either in the presence or absence of added bicarbonate. In the absence of bicarbonate, the two major products formed are 6-hydroxymelatonin and 5-methoxy-2-hydro-pyrroloindole, and the latter is the only major product with excess bicarbonate. A transient purple intermediate with a maximum absorbance at about 520 nm is observed upon mixing solutions containing peroxynitrite and melatonin. These observations indicate that the melatoninyl radical cation is formed in the peroxynitrite/melatonin reaction, providing a direct evidence for the one-electron oxidation ability of peroxynitrite. The melatoninyl radical cation also is observed with excess bicarbonate.
Zhang
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The Biodynamics Institute, Louisiana State University, Baton Rouge, Louisiana, 70803-1800, USA.
Squadrito
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Pryor
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D001639:Bicarbonates / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism*; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism*
D001639:Bicarbonates; D005609:Free Radicals; D009566:Nitrates; C039642:peroxynitric acid; D008550:Melatonin