Similar profile of urinary and faecal metabolites of 14C-carmoisine in male and pregnant female rats after oral administration

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-naphthyl-amine-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.

Reduction rate of 14C-Carmoisine by resting cell bacterial suspension from human and rat faeces

14C-Carmoisine (250/ug; 1.25 x 10(6) dpm) was incubated under strictly anaerobic conditions with resting cell suspension from stool specimens collected from male rats and human male healthy adults. The kinetics of azoreduction was determined as amount of naphthionic acid (NA), the stable metabolite of Carmoisine produced by the activity of the anaerobic bacteria. The analytical determinations were performed by radio-HPLC technique. There were no significant qualitative differences in the radiochromatographic profiles of samples obtained from human and rat flora suspensions. The calculated reduction rates were 5.03 +/- 0.18 nmoles of NA/250/ug protein/min, and 1.72 +/- 0.12 nmoles of NA/250/ug protein/min for rat and human faecal resting cells respectively. From our results it seems that the enzymatic reaction, following zero order kinetics, is similar for the two species and only the reduction rate is different.