Identification of [14C]carmoisine metabolites in bacterial suspension of rat faeces

An in vitro system consisting of a bacterial suspension of human or rat faecal microflora brought about the biological reduction of the red azo dye [ 14C]carmoisine to 1-naphthylamine-4-sulphonic acid (NA) and 2-amino-1-naphthol-4-sulphonic acid (ANA). These metabolites have been unequivocally identified by radio-HPLC, spectroscopic methods, dilution with cold authentic standards and evidence that the specific activity of the diluted compounds remained constant throughout repeated crystallization, acetylation and purification. The results clearly indicated that samples derived from anaerobic incubations have to be processed for analysis in the complete absence of oxygen. In the presence of oxygen, the formation of a complex pattern of compounds in addition to NA was observed as a consequence of the chemical decomposition of ANA.