An LC-ESI/MS/MS method for the determination of lupeol via precolumn derivatization and its application to pharmacokinetic studies in rat plasma.

Lupeol, a phytosterol and triterpene, is widely found in edible fruits and vegetables, and has been reported to exhibit a spectrum of pharmacological activities against various disease conditions. In the present study, a derivative generated by the reaction of lupeol with p-toluenesulfonyl isocyanate was ionizable and fragmentable in the negative mode by electrospray ionization/tandem mass spectrometry. Based on this simple chemical derivatization, a liquid chromatography-electrospray ionization/tandem mass spectrometry method was developed and validated for the quantification of lupeol in rat plasma. The calibration curves were linear (r2 > 0.999) over concentrations from 2.5 to 250 ng/ml for lupeol. The method had an accuracy of 96.0-109.4%, and the intra- and inter-day precisions (RSD) were within ± 15%. The stability data showed that no significant degradation occurred under the experimental conditions. The mean recoveries at three quality control levels were within 88.7-95.7%. No significant matrix effects (105.3-109.8%) were observed in rat plasma. This method was successfully applied to the pharmacokinetic study of lupeol in rat plasma after oral administration.