Carcinogenic azo dyes--detection of new metabolites of 3'-methyl-4-(methylamino)azobenzene in rat bile.

Metabolism of 3'-methyl-4-(methylamino)azobenzene (3'-Me-MAB) in the rat has been investigated by an ion cluster technique. A mixture of non-labeled and deuterium labeled 3'-Me-MAB in cottonseed oil was administered orally with a stomach tube. After administration, the rat bile was collected for 24 hr and enzymically hydrolyzed. This sample was applied to an Amberlite XAD-2 column and the column was washed with water. The metabolites were eluted with methanol and were separated by thin-layer chromatography. The mass spectrum of each metabolite was measured. By means of this technique, the metabolites oxidized at the 3'-methyl group were newly detected in the bile in addition to the N-demethylated, arly hydroxylated, and their azo-reduced metabolites. The effect of the ring methyl group on the carcinogenic action of aminoazo dyes is also discussed.