Simultaneous Determination of Oridonin, Ponicidin and Rosmarinic Acid from Herba Isodi Rubescentis Extract by LC–MS-MS in Rat Plasma

An analytical method was developed for the simultaneous quantification of oridonin, ponicidin and rosmarinic acid in rat plasma using liquid chromatography-tandem mass spectrometry with electrospray ionization in positive and negative ion modes of operation. Multiple reaction monitoring was used for quantification using the precursor to product ion pairs of m/z 359.100 → 160.9 (rosmarinic acid), m/z 150.1 → 106.9 (acetaminophen as internal standard 1), m/z 365.1 → 347.3 (oridonin), m/z 363.3 → 345.2 (ponicidin) and m/z 258.3 → 201.0 (dextrorphan as internal standard 2). Optimum chromatographic separation was achieved with a BDS Hypersil C18 column (100 × 2.1 mm, 2.4 µm) and a mobile phase consisting of acetonitrile-5mM ammonium acetate containing 0.1% acetic acid (25:75, v/v). The analytes were extracted from rat plasma using a single liquid-liquid extraction technique and the calibration curve was linear within the concentration range of 2-1,000.0 ng/mL for three analytes. The extraction recovery was above 70%, the intra-day and inter-day precision of the quality control (QC) samples was less than 12.45% and the accuracy of the QC samples was 96.99-105.79% of the nominal values. The method was sensitive and reliable and was successfully applied to a pharmacokinetic and bioavailability study of Herba Isodi Rubescentis extract in rats.