A method for the quantitative analysis of cudratricusxanthone B (CXB) in rat plasma by high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) has been developed and validated. The method involved liquid-liquid extraction from plasma, simple chromatographic conditions on a Venusil XBP-PH C(18) column with the mobile phase of 0.5% formic acid in methanol, and mass spectrometric detection using an API-3000 instrument. Multiple reaction monitoring (MRM) mode was used to monitor precursor/product ion transitions of m/z 397.1/285.0 for CXB and m/z 381.6/269.2 for the internal standard (I.S.) cudraxanthone H. The standard curves were linear over the concentration range of 1-500 ng/mL for CXB in rat plasma. The intra- and inter-batch accuracy for CXB at four concentrations was 89.4-99.5% and 89.4-100.8%, respectively. The RSDs were less than 7.92%. The lower limit of quantification for CXB was 1.0 ng/mL using 100 microL of plasma. The average extraction recoveries of CXB ranged from 80.1 to 95.4% at the concentrations of 2, 50 and 500 ng/mL, respectively. This method was successfully applied to the pharmacokinetic study after an intravenous administration of CXB in male Sprague-Dawley (SD) rats.
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