Bio-metabolism of green S and indigo carmine through caecal microflora of rats.

Bio-metabolism of two permitted food colours viz., Green S and Indigo Carmine, through caecal microflora of rats was investigated. Incubation of Green S with caecal flora resulted in one coloured and two fluorescent metabolites with the corresponding Rf values of 0.83, 0.33, 0.22, respectively. Indigo carmine was metabolized by caecal microflora to four [corrected] fluorescent metabolites with Rf values of 0.09, 0.27, 0.5 and 0.72. The DI 50 value of Green S was considerably higher (456 min) as compared to that of Indigo carmine (54 min). These results suggest that Green S and Indigo carmine are biotransformed to a variety of metabolites by rat caecal microflora.