Determination of isotoosendanin in rat plasma by liquid chromatography-tandem mass spectrometry: application to pharmacokinetics study.

A rapid, sensitive and accurate liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed and validated for the quantification of isotoosendanin, an important bioactive component isolated from Meliae cortex. A Capcell PAK C18 column (100 × 4.6 mm) was used for the chromatographic elution using methanol-10 mM ammonium acetate-formic acid (80:20:0.1, v/v/v) as mobile phase at the flow rate of 0.6 mL/min. MS-MS analysis was performed on a triple quadrupole mass spectrometer equipped with an atmospheric pressure chemical ionization source in positive ion mode. Extraction of isotoosendanin and genistein (internal standard, IS) from rat plasma was determined by precipitating protein treatment. Quantification was performed by MS in the multiple reaction monitoring mode with positive ionization at m/z 557 → 437 for the analyte and m/z 271 → 215 for IS, respectively. Linear isotoosendanin calibration curves were obtained between 2.0-2,000 ng/mL with a correlation coefficient greater than 0.99. Acceptable precision and accuracy were acquired for concentrations over the standard curve range. Satisfactory results were achieved for sensitivity, specificity, recovery, freeze/thaw and stability. This analytical method was successfully applied to determine the pharmacokinetic parameters of isotoosendanin after an oral administration of 200 mg/kg to rats.

Development and validation of an LC-MS-MS method for determination of methyl kulonate in rat plasma.

A sensitive, rapid and specific LC-MS-MS method was established and validated for determination of methyl kulonate, a major bioactive constituent isolated from Meliae Cortex, in rat plasma. Plasma samples were treated by precipitating protein with methanol and were chromatographed using a Capcell Pak C18 column (100 x 4.6 mm, 5 µm) with the mobile phase comprising a mixture of methanol, 10 mM ammonium formate and formic acid (95:5:0.1, v/v/v). Detection and quantification were performed by mass spectrometry in the multiple reaction monitoring mode with positive atmospheric ionization at m/z 467 --> 311 for methyl kulonate, and m/z 469 --> 451 for dubione B (internal standard), respectively. A good linear response was observed over the concentration range 1.00-500 ng/mL with the lower limit of quantification 1.00 ng/mL in rat plasma. The method also afforded satisfactory results base on sensitivity, specificity, precision, accuracy, recovery, freeze-thaw and long-time stability. The validated method was successfully applied to determine the pharmacokinetic properties of methyl kulonate in rats after oral administration at dose of 100 mg/kg. This pharmacokinetic study of methyl kulonate is reported here for the first time.