Quantitative determination of glaucocalyxin A in rat plasma by LC-MS/MS: Application to a preclinical pharmacokinetic study

A rapid and sensitive LC-MS/MS method for the determination of glaucocalyxin A (GLA) in rat plasma using oridonin as an internal standard was developed and validated. Chromatogram separation was performed on a reversed phase C18 column, using acetonitrile: 2 mM ammonium acetate containing 0.05% formic acid (45:55, v/v) as the mobile phase. Detection and quantification were carried out using a mass spectrometer by the multiple reaction monitoring (MRM) mode with negative electrospray ionization at m/z 331.1 → 313.3 for glaucocalyxin A and m/z 363.3 → 345.4 for IS, respectively. The calibration curves were linear over the range of 5-5000 ng mL^-1, with the limit of quantification (LOQ) 5 ng mL^-1. The intra- and inter-day precisions were less than 12% in terms of relative standard deviation (RSD), and the accuracy was within -1.96 to 8.17 % in terms of relative error (RE). The extraction recoveries ranged from 78.4% to 84.7% for rat plasma and no matrix effect was found in this method. The method was successfully applied to the characterization of the pharmacokinetic profile of glaucocalyxin A (GLA) in rats after following a single intravenous dose (15 mg kg^-1) and three different oral doses (7.5 mg kg^-1, 15 mg kg^-1, and 30 mg kg^-1).