EVIDENCE FOR DIRECT-ACTING OXIDATIVE GENOTOXICITY BY REDUCTION PRODUCTS OF AZO DYES

The intestinal flora forms a complex ecosystem that metabolizes dietar y and endogenous nutrients under primarily anaerobic conditions. The i ngestion of azo dyes has been proposed as one source of potential geno toxic agents. Many intestinal bacteria are able to reduce the azo bond (termed azofission), which liberates the substituted naphthol compoun ds. The standard Ames test has not demonstrated mutagenicity either by various common food colorings or by their reduced end products in Sal monella typhimurium strains TA98 and TA100. In contrast, genetic toxic ity was demonstrated in the Escherichia coli differential kill assay a nd in S. typhimurium TA102 for the reduced dyes. The superoxide free r adical was produced by the azo dyes only after reduction by the intest inal bacteria Enterococcus faecalis and Bacteroides thetaiotaomicron.