Synchronous measuring of triptolide changes in rat brain and blood and its application to a comparative pharmacokinetic study in normal and Alzheimer's disease rats.

Triptolide, a major active ingredient of Tripterygium wilfordii Hook F, provides anti-inflammatory and neuroprotective activities. In this study, a microwave-assisted stable isotope labeling derivatization-magnetic dispersive solid phase extraction (MA-SILD-MDSPE) combined with ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method has been developed for the determination of the triptolide in rat microdialysates. A pair of SILD reagents (d0-/d3-3-N-methyl-2'-carboxyl Rhodamine 6G, d0-/d3-MCR6G) were used to label triptolide in real samples and standards under mild conditions. The introduction of SILD reagents enhanced the sensitivity of MS/MS detection and ensured accurate quantification. A novel molecularly imprinted polymer coating with d0-MCR6G labeled triptolide as template was firstly synthesized by precipitation polymerization method, and used to selectively extract the labeled triptolides from complex matrices. The purified d0-/d3-MCR6G-triptolides were determined by UHPLC-MS/MS analysis. Using the proposed method, a good linearity (R2>0.995), low limits of detection (LOD, 0.45-0.50 pg/mL) and quantification (LOQ, 3.0 pg/mL) were achieved. The intra- and inter-day precision and accuracy were within the acceptable ranges. No significant matrix effect was observed. The derivatization efficiency was more than 96 %. The validated method was successfully applied to a comparative pharmacokinetic study of triptolide synchronously in brain and blood of normal and Alzheimer's disease rats by in vivo microdialysis sampling technique.