Development and validation of a liquid chromatography/tandem mass spectrometry assay for the quantification of methyl protodioscin in rat plasma: application to a pharmacokinetic study

A high performance liquid chromatography/tandem mass spectrometry assay was first developed and validated for the quantification of methyl protodioscin (MPD), a natural furostanol saponin with distinct antitumor activity, in rat plasma with 17 α ‐ethinylestradiol as internal standard (IS). Methanol‐mediated protein precipitation was employed for plasma sample pretreatment. The separation was achieved on a C 18 column (150 × 4.6 mm, i.d., 5 µm) by isocratic elution with methanol–water (72:28, v/v) as mobile phase at a flow rate of 1.0 mL/min. Ion acquisition was performed in selective reaction monitoring positive mode by monitoring the transition of m/z 1085.7 → 1053.7 for MPD, and in selective ion monitoring negative mode by monitoring the deprotonated ion m/z 295.5 for IS. The assay was linear over the concentration range of 2.024–270.0 µg/mL with 2.024 µg/mL as the lower limit of quantification. It was specific, accurate, precise and reproducible with intra‐ and inter‐run RSD <8.3% and RE between −11.5 and 12.8%. The assay was successfully applied to a preclinical pharmacokinetic study after an intravenous dose of 40 mg/kg MPD to rats. Copyright © 2007 John Wiley & Sons, Ltd.