Effects of (+)catechin and (−)epicatechin on heterocyclic amines-induced oxidative DNA damage

Abstract

The aim of the present study was to evaluate the protective effect of (+)-catechin and (-)-epicatechin against 2-amino-3,8- dimethylimidazo[4,5-f]quinoxaline (8-MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]-quinoxaline (4,8-diMeIQx) and 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP)-induced DNA damage in human hepatoma cells (HepG2). DNA damage (strand breaks and oxidized purines/pyrimidines) was evaluated by the alkaline single-cell gel electrophoresis or comet assay. Increasing concentrations of 8-MeIQx, 4,8-diMeIQx and PhIP induced a significant increase in DNA strand breaks and oxidized purines and pyrimidines in a dose-dependent manner. Among those, PhIP (300 µm) exerted the highest genotoxicity. (+)-Catechin exerted protection against oxidized purines induced by 8-MeIQx, 4,8-diMeIQx and PhIP. Oxidized pyrimidines and DNA strand breaks induced by PhIP were also prevented by (+)-catechin. Otherwise, (-)-epicatechin protected against the oxidized pyrimidines induced by PhIP and the oxidized purines induced by 8-MeIQx and 4,8-diMeIQx. One feasible mechanism by which (+)-catechin and (-)-epicatechin exert their protective effect towards heterocyclic amines-induced oxidative DNA damage may be by modulation of phase I and II enzyme activities. The ethoxyresorufin O-deethylation (CYP1A1) activity was moderately inhibited by (+)-catechin, while little effect was observed by (-)-epicatechin. However, (+)-catechin showed the greatest increase in UDP-glucuronyltransferase activity. In conclusion, our results clearly indicate that (+)-catechin was more efficient than (-)-epicatechin in preventing DNA damage (strand breaks and oxidized purines/pyrimidines) induced by PhIP than that induced by 8-MeIQx and 4,8-diMeIQx.