Bioactive microbial metabolites from glycyrrhetinic acid

Biotransformation of 18 beta-glycyrrhetinic acid, using Absidia pseudocylinderospora ATCC 24169, Gliocladium viride ATCC 10097 and Cunninghamella echinulata ATCC 8688a afforded seven metabolites, which were identified by different spectroscopic techniques (H-1, C-13 NMR, DEPT, H-1-H-1 COSY, HMBC and HMQC). Three of these metabolites, viz. 15 alpha-hydroxy-18 alpha-glycyrrhetinic acid, 13 beta-hydroxy-7 alpha,27-oxy-12-dihydro-18 beta-glycyrrhetinic acid and 1 alpha-hydroxy-18 beta-glycyrrhetinic acid are new. The C-13 NMR data and full assignment for the known metabolite 7 beta, 15 alpha-dihydroxy-18 beta-glycyrrhetinic acid are described here for the first time. The major metabolites were evaluated for their hepatoprotective activity using different in vitro and in vivo models. These included protection against FeCl3/ascorbic acid-induced lipid peroxidation of normal mice liver homogenate, induction of nitric oxide (NO) production in rat macrophages and in vivo hepatoprotection against CCl4-induced hepatotoxicity in albino mice. (C) 2009 Elsevier Ltd. All rights reserved.