Soybean soluble polysaccharide enhances absorption of soybean genistein in mice

This study was designed to probe the promoting effects of soybean soluble polysaccharide (SSPS) on bioavailability of genistein in mice and the underlying molecular mechanism. Male Kunming mice (n = 8) were administered intragastrically with either saline, SSPS (5 mg/kg bw), genistein (100 mg/kg bw), or SSPS (5 or 50 mg/kg bw) together with genistein (100 mg/kg bw) for consecutive 28 days. UPLC-qTOF/MS analysis showed that co-administration of SSPS and genistein in mice caused significant elevation in the urinary levels of genistein and its metabolites (p < 0.05). Furthermore, the fecal excretion of genistein was also enhanced by co-administration of SSPS. However, the feces level of dihydrogenistein, a characteristic metabolite of genistein degraded by gut microorganism, was dose-dependently decreased by the combined treatment of SSPS. Additionally, co-treatment of SSPS with genistein also decreased the small intestinal levels of uridinediphosphate-glucuronosyltransferase (UGT), sulfotransferase (SULT), P-glycoprotein (P-gp), multidrug resistance-associated protein-1 (MRP1), and multidrug resistance-associated protein-2 (MRP2) in mice. These findings suggest that the inhibition of SSPS against small intestinal first-pass metabolism of genistein is involved in the promoting effect of genistein bioavailability in mice.