Screening of food dyes for genotoxic activity

Abstract

Twenty-five dyes, selected from the major structural classes of synthetic food colours, currently or previously used in foods, were studied for their abilities to cause DNA damage and mutations in bacterial assay systems, with and without rat-liver microsomal activation. DNA damage, detected as significantly greater toxicity to repair-deficient Escherichia coli strains than to a repair-proficient strain, was induced by phloxine without microsomes and by Red 2G with microsomes. The induction of mutations was studied in liquid fluctuation tests using a tryptophan-requiring E. coli strain (sensitive to base substitutions) and a histidine auxotroph of Salmonella typhimurium (strain TA1538, specific for frameshifts). Brown FK induced base substitutions without activation, and substitutions and frameshifts after activation. Red 2G reverted the E. coli strain only and this specificity for base-substitution induction was verified by testing with S. typhimurium TA1535. The mutagenicity of Red 2G was dependent upon microsomal activation. All the other colourings screened did not induce any detectable effects. The significance of the data is discussed with respect to other information on the mutagenicity and carcinogenicity of food colours.