Determination of oxaceprol in rat plasma by LC-MS/MS and its application in a pharmacokinetic study

A sensitive method for the quantification of oxaceprol in rat plasma using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. Sample pretreatment involved a simple protein precipitation by the addition of 60 μL of acetonitrile-methanol (1:2, v/v) to 20 μL plasma sample volume. Separation was achieved on a Dikma ODS-C18 (5 μm, 150 mm × 4.6mm) reversed-phase column at 40 °C with acetonitrile/0.1% formic acid-4mM ammonium acetate in water (35:65,v/v) at a flow rate of 0.6mL/min. Detection was performed using an electrospray ionization (ESI) operating in negative ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 172 → 130 (oxaceprol) and m/z 153 → 109 (protocatechuic acid, internal standard). The calibration curve of oxaceprol in plasma showed good linearity over the concentration range of 1.25-800 ng/mL. The limit of detection and limit of quantification were 0.400 ng/mL and 1.25 ng/mL, respectively. Intra- and inter-day precisions in all samples were within 15%. There was no matrix effect. The validated method was successfully applied to a preclinical pharmacokinetic study of oxaceprol in rats. After oral administration of 20mg/kg oxaceprol to rats, the main pharmacokinetic parameters T(max), C(max), T(1/2), V(z/F) and AUC(0-t) were 1.4h, 1.2 μg/mL, 2.3h, 19.7 L/kg and 3.4 mg h/L, respectively.