Determination and Pharmacokinetic Study of Pachymic Acid by LC-MS/MS

Poria cocos is a well-known medicinal plant widely used in China and other East Asian countries owing to its various therapeutic effects. Pachymic acid (PA) is a bioactive lanostrane-type triterpenoid from Poria cocos. In this paper, a method of high-performance liquid chromatographic (LC) coupled with triple quadrupole tandem mass spectrometry (QQQ-MS/MS) was developed and validated to investigate the concentration of PA in rat plasma. Samples were prepared by a liquid-liquid extraction, and chromatographic separation was achieved with a Phenomenex Gemini C18 column (50 mm×2.0 mm i.d.) using a mobile phase consisting of acetonitrile and 0.05% formic acid (85 : 15, v/v) at a flow rate of 0.3 mL/min. The detection was performed on an Applied Bio-Systems API 4000 MS/MS with an electrospray ionization (ESI) inlet in negative multiple reaction monitoring (MRM) mode. Standard curves of samples in plasma were linear (R(2)=0.9948) over the concentration range of 5-500 ng/mL, and acceptable accuracy and precision were achieved. The lower limit of quantification and detection were 5 and 0.5 ng/mL, respectively. The method was used successfully to study the pharmacokinetics of PA in rats for oral administration. The main pharmacokinetic parameters of elimination half-life (t1/2), area under the plasma concentration-time curve from time zero to infinity (AUC0→∞), plasma clearance (CL), and apparent volume of distribution (Vd) for the PA group were 4.96±1.33 h, 1466.9±361.7 ng·h/mL, 6.82±1.73 L/h, and 48.85±9.47 L, respectively. This LC-MS/MS method can be developed further for clinical investigation of PA-containing products.