Melibiose, a Nondigestible Disaccharide, Promotes Absorption of Quercetin Glycosides in Rat Small Intestine

We demonstrated that melibiose, a nondigestible disaccharide composed of galactose and glucose with α-1,6 glycoside linkage, promotes the absorption of water-soluble quercetin glycosides in ligated small intestinal loop of anesthetized rats. Water-soluble quercetin glycoside, a quercetin-3-O-glucoside mixture (Q3GM), includes quercetin-3-O-glucoside (Q3G, 31.9%), mono (21.2%) and di (17.1%), glucose adducts with α-1,4 linkages. After instillation of Q3GM into the intestinal loop with or without melibiose, the plasma concentration of quercetin derivatives in the portal blood was considerably higher in the melibiose group at 60 min. Furthermore, we evaluated the hydrolytic rate of Q3G by the mucosal homogenate of the small intestine with six different disaccharides. Melibiose and isomaltose, which have α-1,6 glycoside linkage, were found to promote Q3G hydrolysis to aglycone. These results suggest that melibiose promotes quercetin glycoside absorption in rats by increasing glycoside hydrolysis in the intestinal lumen and that α-1,6 linkage is involved in this process.