Determination of Rhynchophylline in Rat Plasma by Liquid Chromatography Mass Spectrometry and Its Application

A sensitive and selective liquid chromatography mass spectrometry method was developed for the determination of rhynchophylline in rat plasma. After the addition of estazolam as the internal standard (IS), protein precipitation by acetonitrile was used for sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 column (2.1 x 150 mm, 5 mu m) with acetonitrile-0.1% formic acid as the mobile phase with gradient elution. The electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring mode was used for quantification by using target fragment ions m/z 385 for rhynchophylline and m/z 295 for the IS. Calibration plots were linear over the range of 5-500 ng/mL for rhynchophylline in plasma. The lower limit of quantification for rhynchophylline was 5 ng/mL. The mean recovery of rhynchophylline from plasma was in the range of 87.7-92.6%. The coefficients of variation of intra-day and inter-day precision were both less than 11%. This method is sensitive and selective enough to be used in pharmacokinetic research for the determination of rhynchophylline in rat plasma.