The identification of microbial metabolites of sulfolithocholic acid.

Sulfolithocholate a major detoxified form of lithocholic acid, is biotransformed by human intestinal microflora to four major metabolites. Purification of crude extracts by Sephadex LH-20 chromatography gave three major radioactive peaks, after incubation studies, which were characterized by thin-layer and gas--liquid chromatography, as well as combined gas--liquid chromatography--mass spectrometry. Peak I has a polarity similar to that for 3 beta-palmitoyl-isolithocholic acid and transesterification of the metabolite showed that it was a mixture of palmitoyl, palmitoleyl, stearyl, and oleyl esters of isolithocholate. Peak II was identified as chol-3-en-24-oic acid and Peak III was a mixture of lithocholic (mainly) and isolithocholic acids. The fatty acyl derivatives of isolithocholate and delta 3-cholenate are new microbial metabolites of sulfolithocholate and represent unique classes of bile acids that should be included in routine fecal analysis of bile acids.