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

14C-Carmoisine (250 μg; 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 μg protein/min, and 1.72 ± 0.12 nmoles of NA/250 μg 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.