Probing Interactions between β-Glucan and Bile Salts at Atomic Detail by 1H-13C NMR Assays

Polysaccharides are prospective hosts for the delivery and sequestration of bioactive guest molecules. Polysaccharides of dietary fiber, specifically cereal (1 -> 3)(1 -> 4)-beta-glucans, play a role in lowering the blood plasma cholesterol level in humans. Direct hostguest interactions between beta-glucans and conjugated bile salts are among the possible molecular mechanisms explaining the hypocholesterolemic effects of beta-glucans. The present study shows that H-1-C-13 NMR assays on a time scale of minutes detect minute signal changes in both bile salts and beta-glucans, thus indicating dynamic interactions between bile salts and beta-glucans. Experiments are consistent with stronger interactions at pH 5.3 than at pH 6.5 in this in vitro assay. The changes in bile salt and beta-glucan signals suggest a stabilization of bile salt micelles and concomitant conformational changes in beta-glucans.