Localization of enzymes involved in metabolism of glycyrrhizin in contents of rat gastrointestinal tract.
Most digested food 2 h after overnight feeding in rat remained in the stomach, duodenum, upper small intestine, lower small intestine, cecum and colon, all of which indicated pH between 4 and 7 and had glycyrrhizin (GL) hydrolyzing activity. This enzyme activity was highest in the cecal and colonic contents among all gastrointestinal contents. Also, 3 alpha-hydroxyglycyrrhetic acid (3 alpha-hydroxyGA) and 3 beta-hydroxyglycyrrhetic acid (3 beta-hydroxyGA) oxidizing enzymes were localized in the same cecal content. Namely, rat gastrointestinal bacteria had the ability to hydrolyze GL to 3 beta-hydroxyGA by glycyrrizin beta-D-glucuronidase and to oxide 3 beta-hydroxyGA and 3 alpha-hydroxyGA to 3-oxoGA by 3 beta-hydroxyglycyrrhetinate dehydrogenase and 3 alpha-hydroxyglycyrrhetinate dehydrogenase, respectively. In medium of pH 1 to pH 10, metabolites 3 beta-hydroxyGA, 3-oxoGA and 3 alpha-hydroxyGA obtained from the metabolism of GL were the highest in pH 8. The intestinal contents of pH 6 or pH 7 were able to produce metabolites 3 beta-hydroxyGA in the metabolism of GL. However, the stomach content at pH 4.2 was lowest in metabolite 3 beta-hydroxyGA. It is unknown whether or not GL is metabolized to 3 beta-hydroxyGA by the stomach content in vivo.
Akao
T
T
Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
D000818:Animals; D004064:Digestive System / Q000201:enzymology* / Q000378:metabolism / Q000382:microbiology; D004798:Enzymes / Q000378:metabolism; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D019695:Glycyrrhizic Acid; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar
D004798:Enzymes; D019695:Glycyrrhizic Acid; D006034:Glycyrrhetinic Acid