A LC-MS/MS method for the determination of stachyose in rat plasma and its application to a pharmacokinetic study

A sensitive, simple and rapid analytical method based on a liquid chromatography-tandem mass spetrometry (LC-MS/MS) has been established and validated for the determination of stachyose in rat plasma. Plasma samples were prepared by protein precipitation with acetonitrile. Separation of stachyose and nystose (internal standard, IS) was achieved using acetonitrile-water (55:45, v/v) as the mobile phase at a flow rate of 1 ml/min for 6 min on an Asahipak NH2P-50 4E column with an Asahipak NH2P-50G 4A guard column. Detection and quantification were conducted by LC-MS/MS method in the negative ion mode using multiple reaction monitoring (MRM) transitions at m/z [M-H](-) 665.4→383.1 for stachyose and 665.5→485.0 for IS, respectively. The method was linear over the concentration ranges of 100-30000 ng/ml with a lower limit of quantification (LLOQ) of 100 ng/ml. The intra- and inter- day precision were all within 8.7% and the accuracy ranged from 97.2-108.4% and 98.3-102.4%, respectively. Stability studies indicated that stachyose was stable under short-term, long-term and three freeze-thaw storage conditions. The method was successfully applied to a pharmacokinetic study involving pulmonary administration of micronized Rehmannia glutinosa oligosaccharides (RGOS) to rats.