HPLC study on ion-pairing ability of deoxycholic acid epimers

In line with the postulate that the physiological functions of bile acids, in particular their contribution to the regulation of the fat metabolism, may be related to their ion-pairing ability, this paper provides data on the chromatographic aspects related to their ion-pairing ability. The paper provides data about the chromatographic aspects of this subject. The ion-pairing (i.e. HPLC-retention-increasing) effects of the therapeutically applied deoxycholic acid epimers (7-deoxycholic acid, DOG; chenodeoxycholic acid, ChDOC; and ursodeoxycholic acid, UDOC) were studied in a reversed-phase HPLC system. As cationic partner substances, nine quaternary ammonium drug compounds were used as cationic partners The ion-pairing activities of the deoxycholic acids were found to be very strong, and much better than those of anionic ion-pairing agents such as pentanesulfonic acid and caproic acid. The natures of the binding of the DOC epimers by the C-18 surface were also determined. While DOC and ChDOC formed double layers on the surface, UDOC was bound only in a monolayer. The differences in chromatographic behavior are interpreted on a stereochemical basis.