Pharmacokinetic comparisons of different combinations of Shaoyao-Gancao-Decoction in rats: Simultaneous determination of ten active constituents by HPLC–MS/MS

A specific HPLC–MS/MS method was developed and validated for simultaneous determination of ten constituents including albiflorin, oxypaeoniflorin, paeoniflorin, liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, ononin, glycyrrhizin and glycyrrhetinic acid in rat plasma using genistein as an internal standard (IS). The rat plasma samples were prepared by a one-step direct protein precipitation procedure with methanol. HPLC separation was achieved on a Zorbax XDB-C18 column (2.1 mm × 50 mm i.d., 3.5 μm) with gradient elution (A: 0.1% aqueous formic acid; B: methanol with 0.1% formic acid) at a flow rate of 0.5 mL/min in a run time of 7 min. All analytes and IS were detected by multiple reaction monitoring scanning with electrospray ionization in the negative ion mode. Calibration curves showed good linearity (r > 0.998) over a wide concentration range for all analytes. The intra- and inter-day precisions were all within 15% and the accuracies were in the range of −6.2% to 10.1%. The validated method was successfully applied to determination and comparative pharmacokinetics investigation of the ten constituents in rat plasma after oral administration of different combinations (Radix Paeoniae Alba:Glycyrrhiza uralensis = 1:1 or 4:1) of Shaoyao-Gancao-Decoction (SGD) extracts. Pharmacokinetic parameters were evaluated by a compartment model. There were perceptible differences in pharmacokinetic parameters (Cmax, AUC0−t, CL) of the analytes except for liquiritin between the two groups of SGD.