Dual function of (-)-epigallocatechin gallate (EGCG) in healthy human lymphocytes

(-)-Epigallocatechin gallate (EGCG), a catechin polyphenol component, is the main ingredient of green tea extract. Recently, increasing attention has been given to its anti-oxidant effects. However, several studies reported the oxidative effects of EGCG, suggesting that EGCG had a dual function of anti-oxidant and pro-oxidant potentials. In this study, we examined the influences of EGCG on healthy human whole blood lymphocytes and purified blood lymphocytes using a single-cell gel electrophoresis (SCG) assay. The results showed that EGCG suppressed the DNA strand breakage in whole blood lymphocytes at concentrations from 10(-8) to 10(-5) M, while it induced DNA strand breakage at concentration of 10(-3) M. Furthermore, EGCG at concentrations of 10(-6)-10(-4) M suppressed the DNA strand breakage induced by bleomycin (BLM) and H2O2, in whole blood lymphocytes. In the same range of 10(-6)-10(-4) M, EGCG increased DNA strand breakage in purified blood lymphocytes, but suppressed the DNA breakage induced by BLM at lower concentrations from 10(-8) to 10(-7) M. From these findings, we propose that EGCG might have a dual function of anti-oxidant and pro-oxidant in healthy human lymphocytes, which would involved in its inhibitory effects against DNA strand breakage induced by BLM and H2O2. (c) 2006 Elsevier Ireland Ltd. All rights reserved.