Binding of bile salts to soluble and insoluble dietary fibers of seaweeds

: Soluble and insoluble dietary fibers are recognized to have different physiological responses. Therefore, we worked out a new method for binding of bile salts to soluble and insoluble dietary fibers in seaweeds. Dried and pulverized Porphyra yezoensis, Undaria pinnatifida, Laminaria japonica, and Hizikia fusiformis were suspended in cholate, chenodeoxycholate, or deoxycholate solution, and incubated. After centrifugation and then precipitation with ethanol according to the analytical method of soluble and insoluble dietary fibers, the concentration of cholates not binding to both dietary fibers was measured by enzymatic colorimetry. The percentage of bile salts bound to insoluble dietary fiber was higher than that to soluble dietary fiber, because the amount of insoluble dietary fiber was higher in seaweeds. The binding ability of soluble dietary fiber seemed to be greater than that of insoluble dietary fiber. Adsorption of cholate to seaweeds was lower in comparison with chenodeoxycholate and deoxycholate. Thus, seaweed dietary fibers have a different capacity to adsorb cholates.