A solution and solid state study on 2-hydroxypropyl-beta-cyclodextrin complexation with hyodeoxycholic acid

Hyodeoxycholic acid (HDCA) is a 6-alpha dihydroxylated natural bile acid capable of preventing gallstone formation by reducing the bile cholesterol saturation. However, any attempt to enrich the bile acid pool with HDCA have failed owing to the poor solubility of the molecule. To resolve the bioavailability problems, the complexation of HDCA into the HP beta CD cavity was studied in solution (solubility methods, C-13- and H-1-NMR spectroscopy and circular dichroism) and in the solid state (IR spectroscopy, X-ray diffractometry and thermal analysis). According to the results, the HDCA inclusion took place with 1 : 1 stoichiometry. The influence of different preparation methods of the solid complex was evaluated for its potential use in appropriate pharmaceutical formulations to improve the bioavailability of HDCA.