Mutagenicity of 4-aminoazobenzene, N-hydroxy-4-aminoazobenzene, 4-nitrosoazobenzene, 4-nitroazobenzene, and their ring methoxylated derivatives on Salmonella.

The mutagenicities of 4-aminoazobenzene (AAB), N-hydroxy-4-aminoazobenzene, 4-nitroazobenzene, and their 2-, 3-, 4'-methoxyl and 2,5-dimethoxyl derivatives, and 2- and 3-methoxy-4-nitrosoazobenzene were examined on Salmonella typhimurium TA98 and TA100. The activities of AAB dyes upon S-9 metabolic activation were related to their carcinogenic activities in the rat. The potent carcinogen 3-methoxy-AAB was a potent mutagen for both tester strains. The moderate or weak carcinogens 4'-methoxy-AAB and AAb were moderate or weak mutagens for one or both of the tester strains. The non-carcinogens 2-methoxy-AAB and 2,5-dimethoxy-AAB were non-mutagenic. In contrast to AAB dyes, N-hydroxy-AAB dyes showed greater mutagenicity than the mother AAB dyes, without S-9 treatment. 4-Nitroazobenzene dyes and 4-nitrosoazobenzene dyes showed mutagenicity without S-9 treatment, and the activities were related to those of the corresponding N-hydroxy-AAB dyes. All 4-nitroazobenzene dyes were mutagenic in the presence of S-9, suggesting the production of mutagens other than N-hydroxy-AAB dyes by the S-9 treatment. The cytotoxicity of azo dyes to bacteria had no apparent relation to the mutagenic activity of the azo dyes. Incubation of 4-nitroazobenzene dyes with TA100 bacteria yielded N-hydroxy-AAB dyes. The synthesis and properties of new N-hydroxy-AAB dyes, 4-nitroazobenzene dyes and 4-nitrosoazobenzene dyes are described.