Abstract: AIM: To observe the effects of soy isoflavones (SI) on serum lipids, malondialdehyde(MDA)and superoxide dismutase (SOD)of blood and liver in rats fed with high cholesterol diet, and the protective effects of genistein on H2O2 injured ECV304 cell in vitro. METHODS: According to serum cholesterol(TC)level, fifty male Wistar rats were divided into 5 groups, normal control group (NC), high cholesterol control group (HC) and three SI treatment groups. three SI treatment groups were administrated with SI 30, 60, 120 mg/kg intragastrically (ig), and the two control groups were administrated with solvent for 9 weeks. At the end of 2, 4, 9 weeks, serum TC, triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein(LDL)were measured. At the end of treatment, SOD activities in RBC and liver, serum and hepatic MDA levels were measured. Hepatic pathological changes were also observed. We also detected survival rate of ECV304 on H2O2 injure after incubated with different concentrations of genistein with MTT assay. RESULTS: SI 30, 60, 120 mg/kg could not reduce serum lipids levels. Hepatic pathological results were also in consistent with serum lipids. But SOD activities in RBC and liver were improved and serum and hepatic MDA levels were decreased in SI treatment groups (P<0.05, P<0.01). In our study, we also observed that genistein 25, 50, 100μmol/L could protect ECV304 cells injured by H2O2 dose-dependenly. CONCLUSION: Soy isoflavones could not improve serum lipids and prevent hepatic fatty degeneration in cholesterol-fed rats. However, they have antioxidative effects both in vivo and in vitro.

Key words: soy isoflavones, genistein, serum lipids, malondialdehyde, superoxide dismutase, ECV304 cell, hydrogen peroxide