DETERMINATION OF MOLECULAR ASSOCIATIONS OF SOME HYDROPHOBIC AND HYDROPHILIC BILE-ACIDS BY INFRARED AND RAMAN-SPECTROSCOPY

The aim of this study was to analyse the Raman and infrared spectra of eight common mammalian bile acids in order to identify intermolecular interactions between hydroxyl and carbonyl groups. The results are co nsidered in the light of the new hydrophilic/hydrophobic classificatio n of bile acids. The alcohol OH group of the hydrophobic bile acids fo rms different intermolecular bonds. The most hydrophobic bile acid, li thocholic acid forms polymers, and this may explain its very low water solubility. The hydrophilic bile acids have some of their alcohol OH groups free of any intermolecular interaction. The strongly hydrophili c murideoxycholic acid also forms dimers, again consistent with a very low water solubility. The proposed structural arrangements are in agr eement with published crystallographic studies.