C-13 CP MAS NMR-STUDY OF THE INTERACTION OF BILE-ACIDS WITH BARLEY BETA-D-GLUCAN/

Dietary beta-D-glucan is associated with low blood cholesterol levels due to increased excretion of bile acids, but there is little evidence for the mechanism involved in enhanced bile acid clearance. Solid-sta te C-13 NMR spectroscopy has now been used to investigate the possibil ity of specific binding between a representative bile acid salt, glyco cholic acid, and barley beta-glucan. From the similarity in chemical s hift values for beta-D-glucan in the solid and solution states, it is concluded that the beta-D-glucan adopts the same conformation in both states. The dye Congo red is known to form a complex with beta-D-gluca n that can precipitate from aqueous solution. In this case, the format ion of a complex involving specific binding was evidenced by the appea rance in the solid-state spectrum of resonances characteristic of the dye molecule, that otherwise would not be present. In contrast, no res onances characteristic of the bile acid were observed in the solid-sta te NMR spectrum of the mixture of beta-D-glucan and the bile acid salt . These results suggest that the hypocholesterolemic property of beta- D-glucan does not involve a simple binding of bile acid salt molecules to specific sites on the beta-D-glucan polymer. Copyright (C) 1996 El sevier Science Ltd