Quantification of liensinine in rat plasma using ultra-performance liquid chromatography tandem mass spectrometry and its application to a pharmacokinetic study

• A method for the analysis of liensinine has been developed.
• The method is characterised by a linear range of 10–1000 ng/ml liensinine in plasma.
• The method was successfully used to follow the decrease of liensinine with time in rat plasma after intravenous administration.

An ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method was developed to determine liensinine in rat plasma using carbamazepine as the internal standard (IS). Sample preparation was accomplished through a protein precipitation procedure with acetonitrile to 0.1 ml plasma sample. The analyte and IS were separated on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with the mobile phase of acetonitrile and 0.1% formic acid in water with gradient elution at a flow rate of 0.40 ml/min. The injection volume was 6 μl. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) by multiple reactions monitoring (MRM) of the transitions at m/z 611.6 → 206.2 for liensinine and m/z 237.1 → 194.2 for IS. The linearity of this method was found to be within the concentration range of 10–1000 ng/ml with a lower limit of quantification of 10 ng/ml. Only 3.0 min was needed for an analytical run. The matrix effect was 93.8–107.4% for liensinine. The intra- and inter-day precision (RSD %) were less than 9.9% and accuracy (RE %) was within ±10.5%. The recovery ranged from 76.2 to 86.8%. Liensinine was sufficiently stable under all relevant analytical conditions. The method was also successfully applied to the pharmacokinetic study of liensinine in rats. The pharmacokinetic parameters were demonstrated as followed: t1/2 was 8.2 ± 3.3 h, Cmax was 668.4 ± 156.9 ng/ml, and AUC0→∞ was 1802.9 ± 466.4 ng/ml h.