Effects of green tea extract and its components on antioxidant status and activities of xenobiotic metabolizing enzymes of rats

: Dietary administration of green tea extract (GTE) or epigallocatechin gallate (EGCG), quercetin (Qu) or caffeine (Cf) in doses equal to their concentration in GTE led to an increase of serum and liver antioxidant capacity and strengthening stability of microsomal and lysosomal membranes in rats. The antioxidant efficiency of EGCG and Qu was considerably higher than that of GTE. There were significant differences in the effects of EGCG, Qu and GTE on the activities and expression of mRNA for CYP1A1, CYP1A2 and CYP3A1. But feeding both GTE and Cf to rats results in similar elevated activities of CYP1A1, CYP1A2, UDP-glucuronosyl transferase and glutathion transferase. Our results suggest that Cf is the main contributor to GTE effects on activities of xenobiotic metabolizing enzymes.