Interactions of alfalfa plant and sprout saponins with cholesterol in vitro and in cholesterol-fed rats.

The in vitro interactions of saponins from alfalfa plant and alfalfa sprouts with cholesterol and the effects of alfalfa plant and sprout and saponin-free alfalfa plant on diet-induced liver cholesterol accumulation, bile acid excretion, and jejunal and colonic morphology were examined. Cholesterol-saponin interactions have been suggested as mechanisms for the observed hypocholesterolemic effects of alfalfa as well as the changes in intestinal morphology. Alfalfa plant saponins bound significant quantities of cholesterol both from ethanol solution and from micellar suspension. Alfalfa sprout saponins interacted with cholesterol to a lesser but significant extent. Sprout saponins also inhibited growth of Trichoderma viride significantly, another measure of saponin-cholesterol interaction. Bile acid adsorption was greatest for alfalfa plant and was not reduced by removal of saponins from the plant material. The ability of alfalfa to reduce liver cholesterol accumulation in cholesterol-fed rats was enhanced by removal of saponins and alfalfa sprouts did not prevent accumulation. Removal of saponins from alfalfa reduced the changes in intestinal morphology previously reported, but interaction with membrane cholesterol did not appear to be the cause of this effect of saponins. Saponin-cholesterol interaction is an important part of the hypocholesterolemic action of alfalfa but interaction of bile acids with other components of alfalfa may be of equal importance.