Abstract: AIM: To quantify magnesium isoglycyrrhizinate(MGL) and glycyrrhetic acid in the plasma of dog by develoPa simple, rapid, sensitive high-performance liquid chromatography (HPLC-UV) method.METHODS: HPLC-UV methods with wavelength 252 nm were used for the quantitation of MGL and GA in plasma.The concentration of MGL and GA were assayed on a Kromasil ODS-1 C18 column with the column temperature 25 ℃.The mobile phase was a gradient system with 0.1 % diethylamine in water (pH 4.60) and acetonitrile at a flow rate of 1.0 ml·min^-1.RESULTS: There was a good linear response range of 0.2 -2.5 mg·L^-1and 2.5 -100 mg·L^-1, while the limit of quantification was 0.2mg·ml^-1.The relative recovery rate of MGL was 94.3 %-101.9 %, GA 96.4 %-101.9 % (n =5);the absolute recovery rate was MGL 78.7 % -87.0 %, GA 77.5 %-87.7 % (n =5).The intra-day and inter-day variations were all less than 15 % (n =5).The plasma samples preserved in refrigerator is stable at -20 ℃ for 14 days, freeze thawing 3 times and at room temperature for 10 h without degradation.CONCLUSION: This method is shown to be specific, sensitive, reliable and suitable for the quantitative determination of magnesium isoglycyrrhizinate following oral administration in biological sample.

Key words: magnesium isoglycyrrhizinate, glycyrrhetic acid, HPLC-UV, gradient elution