RESUMO
Objective: To investigate the action of low level soybean isoflavones (genistin, genistein and daidzein) on the oxidative modification of lipoproteins in serum. Methods: After a system of lipoprotein oxidation mediated by Cu 2+ was established in a dilute serum, the effects of soybean isoflavones on the course and the end of lipoprotein oxidation could be reflected by monitoring the production of conjugated dienes and thiobarbituric acid-reactive substances (TBARS) respectively when isoflavones were added. Results: After 0.5-10 ?mol/L genistein, daidzein, genistin or ?-tocopherol was added into the lipoprotein system respectively before the oxidation initiated by Cu 2+ , the production of conjugated dienes or TBARS in the system was significantly reduced with a dose-dependent relationship. When the lipoprotein oxidation was initiated by Cu 2+ at 37 ℃ for 1 h or 1.5 h, soybean isoflavones also revealed strong inhibition on the oxidation in a weakening way. In comparison with soy isoflavones, ?-tocopherol had smaller inhibition on the production of conjugated dienes, but had promotion on the increase of TBARS. Conclusion: Lipoprotein oxidative modification in serum was weakened by low level soybean isoflavones, and its action after the oxidation initiated was more effective than that of ?-tocopherol.
