Antioxidant activities and lipid lowering effects of isoflavone in male rabbits

Dietary flavonoids appear to play a role in the prevention of a number of chronic diseases such as cancer and cardiovascular disease and the soy isoflavones have been the focus of particular. Consumption of soy isoflavones may reduce the risk of cardiovascular disease both through reduction in serum lipids and by the antioxidant properties. We have therefore investigate the effects of either 2.5 or 5 mg/kg B.W. doses of isoflavones on the levels of free radicals, lipids and lipoproteins in male New Zealand White rabbits. Animals were orally given 2.5 or 5 mg/kg B.W. doses of isoflavones. The tested doses were given to rabbits every other day for 13 weeks. Treatment with isoflavones caused significant (P<0.05) decrease in the concentrations of free radicals in plasma by 33% and 35%, liver by 18% and 27%, brain by 12% and 33%, testes by 40% and 21%, and kidney by 38% and 20% for 2.5 or 5 mg/kg B.W. doses, respectively, as compared to the control. On the other hand, the activity of glutathione S-transferase (GST) did not change in treated animals as compared to control. Also, results showed that isoflavones caused a significant decrease (P<0.05) in the levels of plasma total lipids (TL) by 16% and 19%, total cholesterol by 20% and 20%, triglyceride (TG) by 18% and 23%, low density lipoprotein (LDL) by 19%, 22%, very low density lipoprotein (VLDL) by 18% and 23%, and LDL:HDL ratio by 36% and 39% for 2.5 or 5 mg/kg B.W. doses, respectively, as compared to the control. While the level of high density lipoprotein (HDL) increased by 29% and 32%. The present results showed that the 5 mg/kg dose of isoflavone seemed to be related to a better plasma lipid and lipoprotein profiles and antioxidant activity.