Quantification of leonurine, a novel potential cardiovascular agent, in rat plasma by liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study in rats.

Leonurine (SCM-198), an alkaloid from Herba Leonuri, has been suggested as a novel cardiovascular agent by pharmacology studies in preclinical stage. In present study, we report a simple, rapid and sensitive high-performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS) for determination of leonurine in rat plasma. Leonurine and its internal standard (IS) n-benzoyl-l-arginine ethyl ester (BAEE) were extracted from plasma samples by one-step protein precipitation with perchloric acid. Chromatographic separation was performed on an Agilent Zorbax SB-C₁₈ column (150 × 2.1 mm, 5 µm) using an isocratic elution with acetonitrile-ammonium acetate buffer (10 mm, pH 4.0; 25:75, v/v) as mobile phase at a flow rate of 0.2 mL/min. Analytes were detected by tandem mass spectrometry in positive electrospray ionization (ESI) mode using multiple reaction monitoring (MRM) with the transitions of m/z 312.3 → 181.1 for leonurine and m/z 307.2 → 104.6 for IS. The calibration curves were linear over the range of 4-256 ng/mL with a lower limit of quantitation (LLOQ) of 4 ng/mL. The intra- and inter-day assay precision (as relative standard deviation) were <15%, except which at LLOQ were <20%, with accuracy in the range 98.73-105.42%. The validated HPLC-MS/MS method was successfully applied to the pharmacokinetic study in rats following oral administration of leonurine.