Abstract: To develop a LC-MS method for the determination of glycyrrhetic acid in human plasma and for evaluation of its pharmacokinetic characteristics．Methods Glycyrrhetic acid in plasma was extracted with ethyl acetate， separated on a C18 column with a mobile phase of methanol(5mmol/L ammonium acetate)water(85∶15，V/V) and analyzed by the LCMS method with ursolic acid(UA) as the internal standard．The target ions were m/z 469.5 for glycyrrhetic acid and m/z 455.6 for internal standard. The fragmentor voltages were 200V for glycyrrhetic acid and 100V for the internal standard. ResultsThe calibration curve was linear over the range of 0.5 to 200ng/mL (r=0.9974). The quantitative limit for glycyrrhetic acid in plasma was 0.5ng/mL, the recovery rate was 76.0% to 80.0%, and the interday and intraday derivations (RSD) were less than 12%. The Cmax and Tmax of glycyrrhetic acid were (95.57±43.06)ng/mL and (10.95±1.32)h after oral administration. Conclusion The assay proved to be sensitive，accurate and convenient and can be applied in the determination of glycyrrhetic acid in human plasma and its pharmacokinetic study．

Key words: Diammoniu glycyrrhizinate, Glycyrrhetic acid, High performance liquid chromatographymass spectrometry, Pharmacokinetics