Antimutagenic activity of isoflavones from soybean seeds (Glycine max Merrill)

Two isoflavones, daidzein (1) and genistein (2), were isolated from soybean hypocotyls. Daidzein and genistein showed a suppressive effect on umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK1002 ag ainst the mutagen 3-amino-1,4-dimethyl-5H-pyrido[4,3b]indole (Trp-P-1), whi ch requires liver metabolizing enzymes. Compound 1 suppressed 73% of the SO S-inducing activity at concentrations <0.74 mu mol/mL, and the ID50 value w as 0.37 mu mol/mL. Compound 2 suppressed 95% of the SOS-inducing activity a t concentrations <0.74 mu mol/mL, and the ID50 value was 0.17 mu mol/mL. Co mpounds 1 and 2 were also assayed with the mutagen 2-(2-furyl)-3-(5-nitro-2 -furyl)acrylamide (furylfuramide) and activated Trp-P-1. In addition to the antimutagenic activities of daidzein and genistein against Trp-P-1, frylfu ramide and activated Trp-P-1 were assayed by an Ames test using S. typhimur ium TA100.