Quantitative determination and pharmacokinetic study of aurantio-obtusin in rat plasma by liquid chromatography-mass spectrometry.

A simple and sensitive liquid chromatography-tandem mass spectrometric method was developed and validated to measure aurantio-obtusin content in rat plasma using rhein as internal standard (IS). The analytes were extracted from plasma by a simple liquid-liquid extraction technique using ethyl acetate as extraction solvent. Chromatographic separation was performed on a Zorbax XDB-C18 column (50 mm × 4.6 mm, 2.1 µm particle size) using the mobile phase consisting of methanol-water (70 : 30, v/v). The detection was achieved by negative ion electrospray ionization in selected reaction monitoring mode, monitoring the transitions m/z 329.1 → 299.2 and m/z 283.1 → 183.0 for aurantio-obtusin and IS, respectively. The assay was linear over a concentration range of 4-4,000 ng/mL with a lower limit of quantification of 4.00 ng/mL for aurantio-obtusin. The intra- and inter-day precision was <6.8%, and the accuracy values were between -1.7 and 7.1%. The validated method was successfully applied to the pharmacokinetics of aurantio-obtusin following intravenous administrations to rats.