THE INTERACTION OF BILIAR ACIDS WITH 2-HYDROXYPROPYL-BETA-CYCLODEXTRIN IN SOLUTION AND IN THE SOLID-STATE

The interaction of two biliar acids (chenodeoxycholic acid and cholic acid) with 2-hydroxypropyl-beta-cyclodextrin (HP beta CD) in solution and in the solid state was studied using different techniques. The for mation of an inclusion complex with a 1 : 1 stoichiometry was suggeste d by the phase solubility studies. Both differential scanning calorime try and X-ray diffractometry exhibited the amorphous state of the comp lex. The inclusion of both biliar acids into the HP beta CD cavity was confirmed by the C-13-NMR studies. Cholic acid showed a weaker affini ty with respect to chenodeoxycholic acid probably owing to the presenc e of a hydroxyl group on C(12) (12 alpha) close to the complexation si te.