A sensitive LC-MS/MS-based bioanalytical method for quantification of salviaflaside and rosmarinic acid in rat plasma and its application in a pharmacokinetic study

A selective and sensitive liquid chromatography tandem mass spectrometry method was developed for the simultaneous determination of salviaflaside and rosmarinic acid in rat plasma. Sample preparation was carried out through liquid-liquid extraction with ethyl acetate using curculigoside as internal standard (IS). The analytes were determined by selected reaction monitoring operated in the positive ESI mode. Chromatographic separation was performed on an Agilent Eclipse Plus C-18 column (100x4.6mm, 1.8m) with a mobile phase consisting of methanol-water-formic acid (50:50:0.1, v/v/v) at a flow rate of 0.3mL/min. The run time was 1.9min per sample and the injection volume was 5L. The method had an LLOQ of 1.6ng/mL for salviaflaside and 0.94ng/mL for rosmarinic acid in plasma. The linear calibration curves were fitted over the range of 1.6-320ng/mL for salviaflaside and 0.94-188ng/mL for rosmarinic acid in plasma with correlation coefficients (r(2)) >0.99. Intra- and inter-day precisions (relative standard deviation) were<13.5%, and accuracies (relative error) were between -8.6% and 14.5% for all quality control samples. The method was validated and applied to the pharmacokinetics of salviaflaside and rosmarinic acid in plasma after oral administration of Prunella vulgaris extract to rats.