Characterization of [6]‐gingerol metabolism in rat by liquid chromatography electrospray tandem mass spectrometry

[6]‐Gingerol is a structural analog of capsaicin, an agonist of the transient receptor potential channel vanilloid 1, which is known to have therapeutic properties for the treatment of pain and inflammation. A selective and sensitive quantitative method for the determination of [6]‐gingerol by HPLC‐ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray tandem mass spectrometry. The chromatographic separation was achieved using a Thermo 100 × 2.1 mm C 8 column combined with an isocratic mobile phase composed of acetonitrile, water and formic acid (80:20:0.1) at a flow rate of 250 μL/min. The mass spectrometer was operating in SRM mode and an analytical range set at 20–5000 ng/mL was used to construct a calibration curve in rat plasma. The interbatch precision (%CV) and accuracy (%NOM) observed were 2.9–10.8% and 98.1–102.1% in rat plasma. Similarly, precision and accuracy in rat liver microsomal suspension were also evaluated at nominal concentrations of 1, 25 and 100 μ m; the precision (%CV) was <3.4% and the accuracy (%NOM) observed ranged from 89.7 to 109.4%. An in vitro metabolic stability study using rat liver microsomes was performed to determine intrinsic clearance of [6]‐gingerol. The results show slow degradation with a T 1/2 of 163 min and relatively low intrinsic clearance suggesting that phase I metabolism may not be a major contributor of the drug clearance. Further analyses were performed to characterize in vitro and in vivo metabolites. Three main phase I metabolites and four phase II metabolites were identified by HPLC‐MS/MS and HPLC‐MSD TOF. However, the results suggest that glucuronidation of hydroxylated [6]‐gingerol is the primary metabolite excreted in rat urine. Copyright © 2011 John Wiley & Sons, Ltd.