The determination of glycyrrhizic acid in Glycyrrhiza uralensis Fisch ex DC. (Zhi Gan Cao) root and the dried aqueous extract by LC-DAD

A rapid, sensitive and specific reversed phase high-performance liquid chromatographic (LC) method with photodiode array detection (DAD) has been developed for the determination of glycyrrhizic acid in both the raw herb and a commercially prepared dried aqueous extract of Glycyrrhiza uralensis Fisch. ex DC. root (Zhi Gan Cao, liquorice). It was determined that extracting the raw herb in aqueous methanol (50:50 v/v) by sonication for 2 x 30 min was the most efficient sample preparation. Baseline resolution of the glycyrrhizic acid peak was achieved on a Varian Polaris RP C18-A (250 mm x 4.6 mm, 5 mu m packing) column using an isocratic mobile phase consisting of 0.5 v/v aqueous phosphoric acid and acetonitrile in the ratio 60:40v/v. Chromatograms were monitored between 200 and 400nm for peak purity assessments, with quantitation performed at 254 nm. Glycyrrhizic acid calibration curves in the concentration range of 14-558 mu g/ml were prepared on the day of analysis. Curve fitting was by the least-squares method, with correlation coefficients of >0.9998 obtained each time. The average recovery at three spike levels (50, 100, 200%) was of 95.91 +/- 1.05% and 98.36 +/- 3.45% (+/- S.D., n = 7) for the spiked raw herb and dried aqueous extract respectively. The limit of detection and limit of quantitation was 0.52 and 1.72 mg/g respectively for the raw herb, and 0.75 and 2.51 mg/g respectively for the dried aqueous extract. Identity confirmation of the chromatographic peak was achieved by (-) electrospray ionisation tandem mass spectrometry. The concentration of glycyrrhizic acid in the root and dried aqueous extract was found to be 31.1 +/- 0.2 and 40.4 +/- 0.3 mg/g (+/- S.D., n = 7) respectively. (C) 2008 Elsevier B.V. All rights reserved.