Objective The increasing recognition of the role for oxidative stress in hepatic disorders has led to extensive investigation on the protection by exogenous antioxidants against hepatic injury.In this study,we choose two typical polyphenol,quercetin and rutin,to investigate the mechanism of induction of cellular antioxidants and phase 2 enzymes in human HepG2 cells.Methods The HepG2 cells were treated with various concentrations of quercetin and rutin for 6 h and 24 h.The activities of NAD(P)H:quinone oxidoreductase(NQO1)in HepG2 cells were measured by 2,6-dichloroindophenol reduction method.The content of superoxide dismutase(SOD)was determined with the method of chemical colorimetry.The protein expressions of NQO1 and NF-E2-related factor 2(Nrf2)in HepG2 cells were detected by Western blotting.Results Incubation of HepG2 cells with quercetin and rutin resulted in a marked concentration-and time-dependent induction of a number of cellular antioxidants and phase 2 enzymes,including NQO1,SOD.Quercetin and rutin treatment of HepG2 cells also caused increase in protein expressions of NQO1 and Nrf2.Conclusions This study demonstrates that a series of phase 2 enzymes in HepG2 cells can be induced by quercetin and rutin in a concentration-and time-dependent fashion by upregulation the protein expression of nrf2. Objective The increasing recognition of the role for oxidative stress in hepatic disorders has led to intense investigation on the protection by exogenous antioxidants against hepatic injury.In this study, we choose two typical polyphenol,quercetin and rutin,to investigate the mechanism of induction of cellular The antioxidants and phase 2 enzymes in human HepG2 cells.Methods The HepG2 cells were treated with various concentrations of quercetin and rutin for 6 h and 24 h.The activities of NAD(P)H:quinone oxidoreductase(NQO1) in HepG2 cells were measured by The 2,6-dichloroindophenol reduction method. The content of superoxide dismutase (SOD) was determined with the method of chemical colorimetry. The protein expressions of NQO1 and NF-E2-related factor 2 (Nrf2) in HepG2 cells were detected by Western blotting. Results Incubation of HepG2 cells with quercetin and rutin resulted in a marked concentration-and time-dependent induction of a number of cellular antioxidants and phase 2 enzymes, including NQO 1, SOD.Quercetin and rutin treatment of HepG2 cells also caused increase in protein expressions of NQO1 and Nrf2.Conclusions this study demonstrates that a series of phase 2 enzymes in HepG2 cells can be induced by quercetin and rutin in a concentration-and time- Dependent fashion by upregulation the protein expression of nrf2.