Protective Effect of Soybean Saponins and Major Antioxidants Against Aflatoxin B1-Induced Mutagenicity and DNA-Adduct Formation

Abstract

Saponins from various plant sources have ben suggested as possible anticarcinogens. Majordietary sources of saponins include legumes such as soybeans. This study was performed todetermine the effect of soybean saponins on aflatoxin B 1(AFB1) induced mutagenicity andAFB1-DNA aduct formation using Salmonella typhimurium and human liver hepatoma(HepG2) cells, respectively. Major antioxidants including L-ascorbic acid, a-tocopherol, all-trans-retinol, and butylated hydroxytoluene (BHT), previously reported to possess antimuta-genic activity, were used as test materials to evaluate the relative effectiveness of saponins.Results indicated antimutagenicity was in the order of BHT . saponins . a-tocopherol .L-ascorbic acid. Soybean saponins exerted a significant effect, inhibiting the mutagenicity ofAFB1 by 52%, 64%, and 81% at concentrations of 60, 90, and 1,20 mg per plate, respectively.The amount of tritiated AFB 1 metabolites DNA aducts formed in HepG2 cells was signif-icantly reduced when cells were preincubated with 10 or 30 mg/ml of test materials. Soybeansaponins inhibited AFB 1-DNA aduct formation by 50.1% at a concentration of 30 mg/ml,whereas L-ascorbic acid and BHT reduced aduct formation by 38.4% and 32.6%, respectively,at the same concentrations. These results indicate that soybean saponins possess not only asignificant antimutagenic activity but a strong inhibitory action against carcinogen-inducedDNA damages. Soybean saponins possibly block the initiation stage of carcinogenesis, andfurther studies are required to elucidate the mechanisms of action.235