Resolution of saturated and unsaturated 5 beta-cholanoic acids by gas-liquid and thin-layer chromatography

The thin-layer and gas-liquid chromatographic properties of the methyl ester acetates were determined for a series of 20 monounsaturated 5 beta-cholanoic acids representing the simple chemical and enzymic dehydration products of the common bile acids. The unsaturated acids were generally indistinguishable from their saturated analogues by thin-layer chromatography on plain silica gel, but resolution was achieved on silica gel impregnated with silver nitrate for compounds having sterically exposed double bonds. The gas-liquid chromatographic behaviour of the unsaturated bile acids on the OV-225, SE-30, and Poly-S-179 liquid phases was closely similar to that observed for the saturated bile acids. The 5 beta-cholenoic acids obeyed the general rules of chromatographic mobility based on the overall shape of the molecule and the number and configuration of functional groups, with a constant retention factor attributable to the olefinic bond. The structural information provided by the chromatographic behaviour of the standard unsaturated bile acids allows a distinction to be made among most of the isomeric 5 beta-cholenoates. A complete identification of all isomeric olefins is possible when chromatographic and mass spectrometric data are combined.