Pharmacokinetic study of multiple active constituents from Kushen–Gancao Decoction after oral administration in rat by HPLC–MS/MS

Kushen–Gancao Decoction (KGD) is a classic traditional Chinese herb combination in treating viral hepatitis and chronic liver diseases. This study aims to investigate the pharmacokinetic (PK) study of matrine (MT), oxymatrine (OMT), glycyrrhizic acid (GL) and glycyrrhetinic acid (GA) following oral administration of KGD in rats. A rapid, sensitive and reliable HPLC–MS/MS method was successfully developed for the simultaneous determination of MT , OMT, GL and GA in rat plasma. A Inertsil C 18 analytical column was used with a gradient mobile phase system of methanol-ammonium acetate (5   mM) with a flow rate of 0.5   mL/min. The analysis was performed on a positive and negative ionization electrospray mass spectrometer via multi reaction monitoring (MRM). Linear calibration curves were obtained for the following concentration range: 10–5000   ng/mL for MT, OMT and GL, 50–15,000   ng/mL for GA in rat plasma ( R 2   >   0.99). The lower limit of quantification (LLOQ) was 5   ng/mL (MT, OMT and GL) and 20   ng/mL (GA). The intra- and inter-day accuracies ranged from −7.91 to 9.10% and precisions (RSD) were within 15%. The analytes were found to be stable under short-term temperature conditions, post-preparative temperature conditions, and after three freeze-thaw cycles conditions. The validated method was successfully applied to a pharmacokinetic study in rats after oral administration of KGD.