In vitro binding of bile acids by soy bean ( Glycine max), black eye bean ( Vigna unguiculata), garbanzo ( Cicer arietinum) and lima bean ( Phaseolus lunatus)

Abstract

The in vitro binding of bile acids by soy bean ( Glycine max), black eye bean ( Vigna unguiculata), garbanzo ( Cicer arietinum) and lima bean ( Phaseolus lunatus) was determined, using a mixture of bile acids secreted in human bile at a duodenal physiological pH 6.3. Six treatments and two blank incubations were conducted, testing substrates on an equal protein basis. Considering cholestyramine as 100 bound, the relative in vitro bile acid bindings for the soy bean, black eye bean, garbanzo and lima bean, on equal protein basis, were 6%, 14%, 47% and 17%, respectively. Relative bile acid binding on equal dry matter (DM), total dietary fibre (TDF) and insoluble dietary fibre (IDF) basis were for soy bean, 2%, 10% and 12%, black eye bean, 3%, 21% and 25%, garbanzo 10%, 68% and 80%, and lima bean 4%, 19% and 23%, respectively. Except for garbanzo, where values were much higher, bile acid bindings by soy bean, black eye bean and lima bean appear to be related to their DM content. These results indicate that bile acid binding by garbanzo > black eye beans=lima beans > soy beans shows their relative health-promoting potential. Incorporation of garbanzo, black eye and lima bean in diets should be encouraged. Data suggest that, of all four kinds of beans tested, bile acid binding may be related to phytochemical (flavonoid, tannin, estrogenic content), anionic, cationic, physical and chemical structure, composition and metabolites, or their interaction with active binding sites. Animal studies are in progress to validate relationship of in vitro binding of various beans observed herein to lipids, cholesterol-lowering and atherosclerosis amelioration.