Interaction of .BETA.-cyclodextrin with bile salts in aqueous solutions.

Abstract

.beta.-Cyclodextrin (.beta.-CD) forms inclusion complexes with bile salts (sodium cholate, sodium deoxycholate, sodium glycocholate and sodium taurocholate) in aqueous solutions. In the presence of bile salts, the gest molecules of .beta.-CD complexes are excluded from the cavity of .beta.-CD and the free molecules increase with the concentration of bile salt up to cmc. Above cmc they are partitioned between the aqueous and micellar phases. Below cmc the exchange reaction proceeds depending on the formation constants of the guest molecule with .beta.-CD and the concentration of bile salt. Above cmc, the free molecules in aqueous phase decrease with increasing concentration of bile salt because of the partitioning to the micellar phase. These results may be related to the absorption of .beta.-CD complexes administered orally and also the matabolism of cholesterol when the complexes are administered orally for a long period of time.