In vitro bile acid-binding ability of black soybean seed coat

Bile acid-binding ability with dietary components is known to modulate cholesterol metabolism. However, the bile acid-binding potential of polyphenols in black soybean (Glycine max L.) seed coat has not yet been fully elucidated. In this study, we quantified the bile acid-binding ability of both black and yellow soybean seed coats and their polyphenols. Suspended seed coat revealed the ability to bind cholic and deoxycholic acids: the binding ability of black soybean seed coat significantly exceeded that of yellow one. This ability was observed in both water-soluble and water-insoluble fractions from black soybean seed coat. The ability of the water-soluble fraction is attributed to anthocyanins and low-molecular-weight proanthocyanidins, whereas that of the water-insoluble fraction is mainly due to highly polymerized proanthocyanidins. These findings suggest that the intake of black soybean seed coat may maintain healthy cholesterol homeostasis through the excretion of bile acids.