Determination of Glycyrrhizin in Dog Plasma by Liquid Chromatography—Mass Spectrometry and its Application in Pharmacokinetic Studies

A sensitive liquid chromatography–electrospray ionization–mass spectrometry (LC-ESI-MS) method was established and validated for the determination of glycyrrhizin in dog plasma. After treatment with methanol to precipitate proteins, plasma samples were analyzed on a reversed-phase C18 (ODS) column with a mobile phase of methanol:1% formic acid solution (75:25, v/v). MS determination was performed using negative electrospray ionization (negative ESI) in the selected ion monitoring mode. Glycyrrhizin was monitored at the m/z 821 channel and the internal standard (gliquidone) at the m/z 526 channel. The calibration curve was linear over the range from 0.05 μg mL⁻¹ to 10 μg mL⁻¹ with a correlation coefficient above 0.99. This method was successfully applied to the pharmacokinetic studies in beagle dogs. The absolute bioavailability of glycyrrhizin in beagle dogs was 3.24%.