The metabolic pathway of sennoside A and B in tied-off gastrointestinal segments of the rat was investigated. The excretion of anthracene derivatives in urine and faeces of the rat after oral administration of the glycosidic compounds has also been studied. For the quantitative determination of rhein in biological samples, a densitometric method on thin-layer chromatograms has been developed.
Sennoside A and B seem to be hydrolyzed by the intestinal microorganisms into the aglycones sennidin A and B, which in turn are metabolised into rhein-9-anthrone and rhein. These metabolites are excreted with the faeces. In the urine, sennidin, rhein and rheinmonoglucuronide were found.