[Detection of an inhibition of benzo(a)pyrene and sodium azide induced mutagenesis by extracts from human feces].

Low levels of mutagenic activities were detected in only 5-25% of the feces of people on a normal mixed-western diet, when feces were extracted by solvents and extracts were analyzed for mutagenicity with Ames' standard Salmonella/microsome assay. Since mutagens are know to be present in this type of diet and may be synthesized endogenously by bacteria in the large bowel, the question is if antimutagenic compounds mask the presence of genotoxic substances. We therefore tested the inhibition of known mutagens--benzo(a)-pyrene and sodium azide--by acetone/ethyl-acetate extracts of lyophilized feces in model experiments. These extracts completely suppressed the mutagenicity of benzo(a)pyrene and reduced the mutagenicity of sodium azide by about 60%, but were non-cytotoxic. Using gel filtration over Sephadex LH-20 and subsequent silica gel column chromatography we found that the inhibitors were polar organic compounds with molecular weights about 500 or more. The inhibitory effect could not be changed by esterification or saponification methods but was completely abolished by alkaline potassium permanganate oxidation. We therefore conclude that the antimutagenic activities might be identical with bile pigments.