Flavonoidler are widely recognized as a naturally occuring antioxidant that can inhibit lipid peroxidation in biological membrane. In this study, the effects of soy isoflavones on the liver damage and the level of plasma paraoxonase with arylesterase activities were investigated on the CCL₄-induced liver damage in rats.

Total of twenty eight male rats were used in the experiments:Group1 (n=7) (control,basal diet for five weeks), group2 (n=7) (basal diet plus oral soyisoflavones (100mg/kg of diet) for five weeks), group3 (n=7) (treated with three times/week i.p.CCL₄ (0.15 ml/100gr of body weight) and basal diet for five weeks,group4 (n=7) (treated with three times/week i.p.CCL₄ (0.15 ml/100gr of body weight) and basal diet plus oral soy isoflavones (100mg/kg of diet)for five weeks.

Plasma Malondialdehyde (MDA) and paraxonase, arylesterase and biochemical parameters were measured with appropriate methods.

The level of MDA was higher in plasma of group3 than group1,2 and group4(respectively P<0.01, P<0.01, P<0.05). The level of liver tissue MDA was significantly increased in group2 compared to group1,2 and group4 (P<0.01). There was a significant reduction in plasma and liver MDA in group4 compared to group3 (P<0.05). The level of plasma paraoxonase and arylesterase activities were lower in group3 than group1 and group4 (p<0.05).There was a inverse correlation between level of plasma MDA and paroxonase in group3 and group4 (r:-0.537, P<0.01, r: -487 P<0.01).

Our findings suggest that soy isoflavones, have an antioxidative effect, soy isoflavones treatment helped to prevent oxidative injury by stimulating some antioxidant enzymes, paraoxanase.