Quantitative determination of corosolic acid in rat plasma by LC-MS/MS-ESI: application to a pharmacokinetic study

A sensitive and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of corosolic acid (CRA) in rat plasma. The plasma samples were prepared by a simple protein precipitation treatment. Chromatographic separation was performed on an Agela MG-C18 column (50 mm × 4.6 mm; i.d., 5 μm) at 30°C. The mobile phase consisting of methanol-10 mM ammonium acetate-formic acid (80:20:0.1, v/v/v; pH=3.8) was delivered with a flow rate of 0.6 ml/min and a running time of 2.5 min. Quantification was performed with positive electrospray ionization (ESI) in the multiple-reaction monitoring (MRM) mode at m/z 490 → m/z 205 for CRA, and m/z 471 → m/z 203 for TEOA (internal standard, IS), respectively. Linearity was evaluated over the concentration range of 1.00-1000 ng/ml with a lower limit of quantification (LLOQ) of 1.00 ng/ml. The validated method was successfully applied to the pharmacokinetic study of CRA after the drug was orally administered in Sprague-Dawley rats.