A simple and accurate liquid chromatography coupled with tandem mass spectrometry method was developed for determination and in vivo pharmacokinetic studies of vitexin rhamnoside in rat plasma. After protein precipitation using methanol, the analytes were separated by a Luna C(18) column with an isocratic elution and analyzed by mass spectrometry in multiple reaction monitoring mode using the respective negative ion at m/z 577.2-293.0 for vitexin rhamnoside and m/z 593.2-413.0 for internal standard (IS) vitexin glucoside. The method was validated systematically within the concentration range 5-5000 microg/L (R > 0.996) and the lower limit of quantitation was 5 microg/L. Acceptable precision and accuracy were acquired for concentrations over the standard curve range. It was further applied to assess pharmacokinetics and bioavailability of vitexin rhamnoside after intravenous and oral administration to rats. The oral bioavailability of vitexin rhamnoside was only 3.57%, which indicated that vitexin rhamnoside had poor absorption or underwent extensive first-pass metabolism. Practical utility of this new LC/MS/MS method was confirmed in pilot pharmacokinetic studies in rats following both intravenous and oral administration.
(c) 2007 John Wiley & Sons, Ltd.