Development and validation of an LC-ESI-MS/MS method for the determination of nitidine chloride in rat plasma

A new liquid chromatography-electrospray ionization-mass/mass spectrometry (LC-ESI-MS/MS) assay method has been developed and validated for the quantification of nitidine chloride (NC), an anti-cancer bioactive substance of Zanthoxylum nitidum (Roxb.) DC. plants, in rat plasma using carbamazepine as an internal standard (I.S.). The NC and I.S. were extracted from rat plasma by acetonitrile protein procedure. Chromatographic separation was carried out with a C(18) column (2.1 mm × 150 mm, 3 μm) with a security guard C₁₈ column (4 mm × 20 mm, 3 μm). The mobile phase consisted of acetonitrile-10 mM ammonium acetate buffer solution-formic acid (35:65:0.2, v/v/v) and delivered at the flow rate of 0.25 mL/min. LC-ESI-MS/MS was performed on a triple-quadrupole mass spectrometry equipped with electrospray ionization (ESI) and positive multiple reaction monitoring (MRM). Target ions were monitored at [M](+)m/z 348.2 for NC and [M]⁺ m/z 237.2 for I.S. The method was linear over the concentration range of 5.0-1500.0 ng/mL. The intra- and inter-day relative standard deviations of the assay were less than 5.0%. The lower limit of quantification was 5.0 ng/mL. The developed method was successfully applied to the estimation of the pharmacokinetic parameters of NC by intravenous administration to rats.