Determination of songorine in rat plasma by UPLC-MS/MS: Assay development and application to pharmacokinetic study

An ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed and validated for the determination and pharmacokinetic investigation of songorine in rat plasma. Sample preparation was accomplished through a simple one-step deproteinization procedure with 0.2mL of acetonitrile to a 0.1mL plasma sample. Plasma samples were separated by UPLC on an Acquity UPLC BEH C18 column using a mobile phase consisting of acetonitrile-0.1% formic acid in water with gradient elution. The total run time was 3.0min and the elution of songorine was at 1.68min. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with positive-ion electrospray ionization (ESI) by multiple reaction monitoring (MRM) of the transitions at m/z 358.3→340.3 for songorine and m/z 237.2→194.3 for carbamazepine (internal standard). The calibration curve was linear over the range of 1-1000ng/mL with a lower limit of quantitation (LLOQ) of 1.0 ng/mL. Mean recovery of songorine in plasma was in the range of 75.2-87.5%. The intra- and inter-day precision (RSD) was between 3.1-8.5% and 4.3-9.6% and the intra- and inter-day accuracy (RE) ranged from -4.0 to 8.9% and -9.0 to 6.7%. This method was successfully applied in pharmacokinetic study after intravenous administration of 5.0mg/kg songorine in rats.