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 miz 526 channel. The calibration curve was linear over the range from 0.05 mu g mL(-1) to 10 mu g 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%.