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 gallate esters to decrease peroxynitrite-induced nitration of tyrosine and to limit surface charge alteration of low density lipoprotein (LDL) was investigated. All compounds tested were found to be potent peroxynitrite scavengers preventing the nitration of tyrosine. The ability of the catechin polyphenols at 10 mu M to minimise tyrosine nitration induced 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%) > catechin (23.9 +/- 5.4%) approximate to epicatechin (22.9 +/- 3.3%) approximate to EGC (19.9 +/- 2.0%). Trolox (10 mu M) was used as the standard for comparative purposes and was found to be less effective than the polyphenols in inhibiting tyrosine nitration (13.6 +/- 2.9%). The catechin polyphenols were also found to offer protection from peroxynitrite-induced modification of critical amino acids of apolipoprotein B-100 of LDL which contribute towards its surface charge. (C) 1997 Academic Press.