Identification of glucosinolate congeners able to form DNA adducts and to induce mutations upon activation by myrosinase

Abstract

Juices from Brassicales are mutagenic in Salmonella typhimurium and characteristic adducts are formed with the endogenous DNA in Brassicales homogenates. These effects require myrosinase activity, suggesting an involvement of breakdown products of glucosinolates (GLs). We aimed to identify GLs congeners producing these effects. We investigated twelve individual GLs for mutagenicity in S. typhimurium TA104 and TA100 and for adduct formation with herring sperm DNA using the 32P-postlabelling/thin-layer chromatography method. All bacteriotoxic and mutagenic effects observed required the presence of myrosinase. Neoglucobrassicin, 4-methoxyglucobrassicin and sinalbin showed mutagenicity over wide concentration ranges, with neoglucobrassicin being the most potent congener. Six other GLs led to modest increases in the number of revertants in a small concentration range, before toxicity overshadowed this effect. The remaining three GLs showed some toxicity, but no mutagenicity. However, all twelve GLs formed DNA adducts. Clearly the highest adduct levels were detected with the indole GLs tested. They matched the major adduct spots formed in Brassicales homogenates. The observation that GLs are genotoxic demands follow-up studies on possible genotoxic and carcinogenic effects of these common food compounds in animal models and humans. Our study may be used to prioritize the congeners in further studies.