Potent antimutagenic and their anti-lipid peroxidative effect of kaikasaponin III and tectorigenin from the flower of Pueraria thunbergiana

The MeOH extract of Pueraria thunbergiana (Leguminosae) flowers and its fractions were subjected to Ames test to test the antimutagenicity. EtOAc fraction (1 mg/plate) decreased the number of revertants of Salmonella typhymurium TA100 by 95% against aflatoxin B-1 (AFB(1)). Phytochemical isolation of the EtOAc fraction afforded four isoflavonoids (tectorigenin, glycitein, tectoridin and glycitin) and one saponin (kaikasaponin III). Though the three isoflavonoids other than tectoridin showed significant antimutagenicity, the activity of kaikasaponin III was the most potent. Kaikasaponin III (1 mg/plate) decreased the number of revertants of S. typhymurium TA100 by 99% against AFB(1) but by 75% against N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Tectodgenin (1 mg/plate) inhibited the AFB(1)-induced mutagenicity by 90% and MNNG-induced one by 76%. Glycitein and glycitin were less active than tectorigenin and kaikasaponin III. This result suggested that kaikasponin III prevents the metabolic activation of AFB(1) and scavenge electrophilic intermediate capable of mutation. The two components with potent activities, tectorigenin and kaikasaonin III, significantly prevented the malondialdehyde formation caused by bromobenzene in the rat.