PROTEIN SAPONIN INTERACTION AND ITS INFLUENCE ON BLOOD-LIPIDS

Protein source and saponins have been shown to influence lipid metabol ism; however, little is known regarding the chemical interactions betw een proteins and saponins or the impact of addition of dietary saponin s to different proteins on cholesterolemia. In the present study, quil laja saponin was added to casein and to isolated soy protein (ISP) and the saponin-protein interaction was investigated by gel electrophores is and fluoroscopy. The impact on cholesterol metabolism also was inve stigated in gerbils. Results from the interaction studies showed that high molecular weight complexes were formed gradually between saponins and caseins, with beta-casein being most susceptible. The resulting c omplexes differed drastically in charge and molecular weight. In contr ast, soy proteins formed in soluble aggregates during heating independ ently of the presence of added quillaja saponin. Data from the animal study showed that addition of saponin to ISP did not affect serum lipi ds, while addition of saponin to casein resulted in significant decrea ses of LDL cholesterol and LDL/HDL ratios, resulting in values similar to those of ISP-fed animals. These results indicate that the effect o f saponins on serum lipid profiles is dependent on the source of dieta ry protein. This could be explained by the finding that quillaja sapon in reacted differently with caseins as compared to soy protein isolate .