Determination of bullatacin in rat plasma by liquid chromatography-mass spectrometry

A liquid chromatography-mass spectrometry method has been developed and validated for the quantification of bullatacin, a bistetrahydrofuran annonaceous acetogenin, in rat plasma. Squamostatin-A was selected as the internal standard. Analytes were extracted from rat plasma by liquid/liquid extraction using ethyl acetate with high efficiency. The chromatographical separation was performed on an Agilent Zorbax SB-C₁₈ column (150 mm × 2.1 mm, 5 μm). The mobile phase consisted of methanol and deionized water (95:5, v/v) containing 0.01% (v/v) formic acid. The chromatographic run time was 7 min per injection and flow rate was 0.2 mL/min. The retention time was 3.22 and 5.23 min for internal standard and bullatacin, respectively. The elutes were detected under positive electrospray ionization and the target analytes quantified by selected ion monitoring mode (645.9 m/z for bullatacin and 661.9 m/z for squamostatin-A). The method was sensitive with the limit of quantitation at 0.5 ng/mL in 100 μL of rat plasma. Good linearity (r²=0.9998) was obtained covering the concentration of 0.5-2000 ng/mL. The intra- and inter-day assay precision ranged from 3.2 to 8.7% and 2.7 to 9.2%, respectively. In addition, the stability, extraction recovery and matrix effect involved in the method were also validated. This method was applied to measure the plasma bullatacin concentrations after a single tail vein intravenous administration of bullatacin in rats.