NMR ANALYSIS AND HYDROLYSIS STUDIES OF GLYCYRRHIZIC ACID, A MAJOR CONSTITUENT OF GLYCYRRHIA GLABRA

From the commercial extract of the roots of Glycyrrhia glabra, a triterpene glycoside was isolated which was characterized as 18β-glycyrrhetinic acid-3-O-β-D-glucuronopyranosyl-(1→2)-β-D-glucuronide; also known as Glycyrrhizic acid or Glycyrrhizin. The complete 1H and 13C NMR assignments of Glycyrrhizin were achieved by the extensive 1D and 2D NMR (1H and 13C, COSY, HMQC, and HMBC) as well as mass spectral data. Further, hydrolysis studies were performed on Glycyrrhizin to identify aglycone and sugar residues in its structure. Further, configuration of sugar moieties in the triterpene obtained during the course of acid hydrolysis studies were confirmed by preparing their corresponding thiocarbamoyl-thiazolidine carboxylate derivatives with L-cysteine methyl ester and O-tolyl isothiocyanate and in comparison of their retention times with standard sugars.