Acaciaside A and B, two acylated triterpenoid bisglycoside saponins originally isolated from the funicles of Acacia auriculiformis, are known to have antihelmintic activity. In our previous investigation it was suggested that the conjugated unsaturated system of the saponins is involved in producing the damaging effect of saponins, probably by resulting free radicals that induce membrane damage through peroxidation. Here the interaction of saponins and the microsomal membrane was investigated in the presence and absence of superoxide dismutase, catalase and thiourea. Our results showed that superoxide dismutase significantly blocked the effect of saponins-induced membrane damage. Catalase had only a minor effect on saponins-induced membrane damage and thiourea had no effect. The results suggest that in our model, saponins can generate superoxide anions and initiate lipid peroxidation.