Abstract
β-Glucuronidases of mammalian tissues metabolized glycyrrhizin (18β-glycyrrhetinic acid, β-D-glucuronyl α-D-glucuronic acid, GL) to glycyrrhetinic acid (GA) via 18β-glycyrrhetinic acid α-D-glucuronic acid (GAMG); they hydrolyzed β-glucuronic acid conjugates better than α-glucuronic acid conjugates. However, human intestinal bacteria directly metabolized GL to GA, and minorly to GA via GAMG. Bacteroides J-37, isolated from human intestinal bacteria, transformed GL or GAMG to GA, but not baicalin; it produced α-glucuroniase, which hydrolyzed the α-linkage of glucuronic acid conjugates. α-Glucuronidase of Bacteroides J-37 hydrolyzed α-glucuronic acid conjugates better than β-glucuronic acid conjugates. β-Glucuronidase from E. coli, a human intestinal bacterium, hydrolyzed baicalin to baicalein, but did not transform GL.
