(-)-EPIGALLOCATECHIN GALLATE, A POLYPHENOLIC TEA ANTIOXIDANT, INHIBITS PEROXYNITRITE-MEDIATED FORMATION OF 8-OXODEOXYGUANOSINE AND 3-NITROTYROSINE

Reaction with peroxynitrite at pH 7.4 and 37 degrees C was found to in crease the 8-oxodeoxyguanosine levels in calf thymus DNA 35-38-fold. T his oxidation of deoxyguanosine, as well as the peroxynitrile-mediated nitration of tyrosine to 3-nitrotyrosine, was significantly inhibited by ascorbic acid, glutathione and (-)-epigallocatechin gallate, a pol yphenolic antioxidant present in tea. For 50% inhibition of the oxidat ion of deoxyguanosine to 8-oxodeoxyguanosine, 1.1, 7.6 or 0.25 mM asco rbate, glutathione or (-)-epigallocatechin gallate, respectively, was required. For 50% inhibition of tyrosine nitration, the respective con centrations were 1.4, 4.6 or 0.11 mM. Thus, (-)-epigaliocatechin galla te is a significantly better inhibitor of both reactions than either a scorbate or glutathione. Reaction of (-)-epigallocatechin gallate with peroxynitrite alone resulted in the formation of a number of products . Ultraviolet spectra of two of these suggest that the tea polyphenol and/or its oxidation products are nitrated by peroxynitrite.