INHIBITION OF PEROXYNITRITE-MEDIATED TYROSINE NITRATION BY CATECHIN POLYPHENOLS

Peroxynitrite is a cytotoxic species generated by the reaction between superoxide and nitric oxide. The ability of catechins and their galla te esters to decrease peroxynitrite-induced nitration of tyrosine and to limit surface charge alteration of low density lipoprotein (LDL) wa s investigated. All compounds tested were found to be potent peroxynit rite scavengers preventing the nitration of tyrosine. The ability of t he catechin polyphenols at 10 mu M to minimise tyrosine nitration indu ced by peroxynitrite (500 mu M) was ECG (38.1 +/- 3.6%) approximate to EGCG (32.1 +/- 7.5%) approximate to gallic acid (32.1 +/- 1.9%) > cat echin (23.9 +/- 5.4%) approximate to epicatechin (22.9 +/- 3.3%) appro ximate to EGC (19.9 +/- 2.0%). Trolox (10 mu M) was used as the standa rd for comparative purposes and was found to be less effective than th e polyphenols in inhibiting tyrosine nitration (13.6 +/- 2.9%). The ca techin polyphenols were also found to offer protection from peroxynitr ite-induced modification of critical amino acids of apolipoprotein B-1 00 of LDL which contribute towards its surface charge. (C) 1997 Academ ic Press.