HPLC-ESI-MS/MS validation and pharmacokinetics of kalopanaxsaponin A in rats

Kalopanaxsaponin A (KPS-A) is a potential anti-tumor active compound isolated from the stems of Stauntonia obovatifoliola Hayata subsp. intermedia. A rapid and accurate high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was firstly developed and validated for the quantification of KPS-A in rat plasma. The plasma samples were pretreated by a simple protein precipitation (PPT) procedure with methanol : acetonitrile (1 : 1, v/v). Chromatographic separation was successfully accomplished on an Agilent Zorbax XDB C-18 column (2.1 mm x 50 mm, 3.5 mu m) with a gradient elution system composed of a 0.1% formic acid aqueous solution and 0.1% formic acid in an acetonitrile solution. The flow rate was set to be 0.50 mL min(-1). The multiple reaction monitoring (MRM) was based on the transitions of m/z = 749.4 -> 585.5 for KPS-A and 268.9 -> 158.8 for genistein (IS). The assay was validated to demonstrate the selectivity, linearity, recovery, accuracy, precision and stability. The lower limit of quantification (LLOQ) was 0.50 ng mL(-1) in 25 mu L of rat plasma. The developed and validated method has been successfully applied to the quantification and pharmacokinetic study of KPS-A in rats after intravenous and oral administration of KPS-A. The oral absolute bioavailability (F) of KPS-A was calculated to be 0.006 +/- 0.002%, suggesting its very poor absorption and/or strong metabolism in vivo.