Gastrointestinal activity of saponins from soy and tomato

Abstract

Saponins, a structurally diverse family of secondary plant metabolites, have been suggested to possess anti‐carcinogenic, hypolipemic, hypocholesterolemic, and immune‐enhancing activities. We have initiated studies to compare the effects of saponins extracted from soy (soyasaponin A and B), tomato, and a commercial mixture of phytosterols (positive control) on GI absorption and metabolism of cholesterol and on interactions between microflora and the gut epithelium. During simulated gastric and small intestinal digestion, saponins from tomato and the phytosterol mix significantly inhibited micellarization of cholesterol (14 µM) from a food matrix (ratio of saponins/phytosterols to cholesterol was approximately 1:6.5). Saponins from soy and tomato, as well as phytosterols, also significantly impaired the transfer of cholesterol from Tween micelles to differentiated cultures of human intestinal Caco‐2 cells. Additionally, as saponins share structural similarity with bile salts that repress the transcription of Salmonella enterica invasion gene regulator sirC, studies examining the influence of dietary saponins on the transcription of sirC and on the influence of the bacterium with Caco‐2 cells are ongoing and will be reported Supported by OARDC and USDA BARD grant.