Mutagenicity of metabolites of carcinogenic aminoazo dyes

The mutagenicity of 8 azo dyes and 6 p-phenylenediamine derivatives, which comprised the metabolites of carcinogenic 4-aminoazobenzene derivatives, was studied on Salmonella typhimurium TA98 and TA100. 4'-Hydroxy-N-methyl-4-aminoazobenzene and its O-sulfate and O-glucuronide, and 3-hydroxy-4-aminoazobenzene were mutagenic on TA98 in the presence of S-9 mix. p-Phenylenediamine and its o-methoxyl derivative were definitely mutagenic on TA98 with the addition of S-9 mix. All metabolites tested were non-mutagenic on TA100, although the mother azo dyes were mutagenic both on TA98 and TA100 in the presence of S-9 mix. These results rule out a possibility that the mutagenicity, at least on TA100 microbes, of carcinogenic 4-aminoazobenzene derivatives may be mediated by any of the ring-hydroxyl or azo reduction metabolites and their conjugates produced from the azo dyes by incubation with S-9 mix.