Pharmacokinetic Study of Swertisin by HPLC-MS/MS After Intravenous Administration in Rats

A sensitive and reliable high-performance liquid chromatography with tandem mass spectrometry was developed and validated for the quantification of swertisin in rat plasma. The samples were prepared with methanol by protein precipitation. Swertisin was separated by using an Agilent Poroshell 120 EC-C₁₈ column (4.6 mm × 50 mm, 2.7 μm) with the mobile phase consisted of acetonitrile and water containing 0.1% formic acid running at a flow rate of 0.3 mL/min for 5 min. The analytes were detected with the multiple reaction monitoring in the negative electrospray ionization source for quantitative response of swertisin [M-H]^- (445.1→281.7) and puerarin (internal standard) [M-H]^- (415.1→295.0). Precision (relative standard deviation, RSD%) of the inter-day and the intra-day was <9.89% and 11.34% while accuracy (relative error, RE%) ranged from -6.01% to 4.92% and -3.97% to 4.39%, respectively. Interestingly, the expression of the γ-aminobutyric acid (GABA) receptor subunits (GABA_Aα₁, GABA_Aα₅ and GABA_Aβ₁) mRNAs was enhanced in the rat hippocampal neurons treated with swertisin as analyzed by real-time polymerase chain reaction. Moreover, the method was successfully applied to determine the pharmacokinetic of swertisin in rats after tail vein injection with 4.0 mg/kg of the compound. Our results provide useful pharmacokinetic information for swertisin in vivo and suggest that the sedative function of this compound may be through inducing the expression of the GABA_A receptor subunits.