Thin-layer and gas--liquid chromatographic identification of neutral steroids in human and rat feces

Natural steroids from rat and human feces were fractionated by sequential thin-layer chromatography (TLC) on Florisil, silica gel, and silver nitrate-impregnated silica gel and analyzed by gas--liquid chromatography (GLC). Cholesterol, coprostanol, and coprostanone accounted for more than 95% of the endogenous neutral steroid in human feces, the remainder being predominantly cholestanol. In addition, evidence was obtained for the presence in human feces of trace amounts of epicoprostanol and cholestanone. In rat feces, several cholesterol precursors that probably originated in the skin (and were ingested during fur=licking) were detected in relatively large amounts, accounting for as much as 27% of the total fecal neutral steroids, whereas these steroids were quantitatively trivial in human feces. As with cholesterol, the major dietary plant sterols (sitosterol, campesterol, and stigmasterol) were converted by intestinal bacteria to the corresponding coprostane and ketonic derivatives during intestinal transit in both human beings and rats. This combined use of TLC and GLC provided for the separation of steroids of endogenous and dietary origin that could not be resolved by either system alone. A majority of the fecal steroids could be tentatively identified by their chromatographic behavior in different TCL systems and on GLC, even when reference standards were unavailable.