Preparation of Glycyrrhetinic Acid Monoglucuronide by Selective Hydrolysis of Glycyrrhizic Acid via Biotransformation

ObjectiveTo search for the microorganisms which have the high selectivity of hydrolyzing glycyrrhizic acid (GL) into 18β-glycyrrhetinic acid-3-O-β-D-glucuronide (GAMG) without glycyrrhetinic acid (GA) byproduct.MethodsGL was biotransformed by Aspergillus sp., the products were separated by chromatography on reverse phase C18 column and semi-preparative HPLC, and their structures were elucidated on the basis of HR-ESI-MS, 1D NMR (1H-NMR, 13C-NMR, and NOESY) and 2D NMR (1H-1H COSY, HSQC, and HMBC) spectral analyses.ResultsAspergillus sp. could partially hydrolyze GL into GAMG (3), along with two minor byproducts, 3-O-β-D-glucurono-pyranosyl-18β-liquiritic acid (1) and 3-O-β-D-glucuronopyranosyl-24-hydroxy-18β-glycyrrhetinic acid (2).ConclusionAspergillus sp. has the high selectivity of hydrolyzing GL into GAMG without GA byproduct and the yield of GAMG is about 60%. The complete assignments of 1H-NMR and 13C-NMR data for compounds 1 and 2 are reported for the first time.