Comparison of in-vitro binding of bile salt by pectins from various sources

Binding of bile salts by dietary fiber is believed to promote their excretion and hence to reduce the serum cholesterol level in man and experimental animals. In this study, the binding efficiency of soluble pectin from various sources, i.e., apple, citrus and pomelo, was examined. Sodium deoxycholate and sodium cholate hydrate were used as a model to represent bile salt in human body. The binding efficiency was assayed by acid reaction, thin layer chromatography (TLC) and enzyme cycling method. The results demonstrated that enzyme cycling method was the most suitable for assaying the in-vitro binding of bile salts while the TLC was not very sensitive, i.e., low amount of bile salts cannot be detected by TLC. Excess pectin from binding test could also interfere the acid reaction method even though the centrifugation was used to remove the excess pectin. When the concentration of pectin was increased, the binding efficiency with sodium deoxycholate increased. However, at 1% w/w of pectin, the binding efficiency decreased. The exception is for pomelo pectin in which the binding efficiency increased when the pectin concentration increased. With sodium cholate hydrate, only slight difference in binding efficiency was observed for all types and concentrations of pectin. The results indicate that the ability to bind bile salts of pectin might be responsible for its hypocholesterolemic action observed in experimental animals and humans.