Ultrahigh-performance liquid chromatography/tandem mass spectrometry method for evaluating enzyme activity and screening inhibitors of cyclooxygenase-2

RATIONALE: Prostaglandin E-2 is an important biomarker in many biological systems. The development of sensitive and reliable analytical methods for monitoring PGE(2) contents in various samples is of great interest. Here we developed an improved method for evaluating the enzyme activity and screening COX-2 inhibitors using ultrahigh-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) combined with PGE(2) derivatization. METHODS: Girard's reagent-T was used as the derivatization reagent and the reaction conditions were optimized. The established method was performed to screen the COX-2 inhibitors from effective constituents of herbs and detect the concentration of PGE(2) in biological tissue samples (liver and kidney). The IC50 values of celecoxib, rofecoxib, sinomenine, bulleyaconitine A, tetrandrine, fangchinoline, berberine hydrochloride and sophocarpidine towards COX-2 were determined. RESULTS: This method improves the quantitative ability for PGE(2), including the linearly dependent coefficient, linearity range and limit of detection. After derivatization, the derivatized PGE(2) could be detected in positive ion mode of electrospray ionization (ESI), which improves the detection sensitivity 10-fold compared to that of the direct detection of underivatized PGE(2) in negative ESI mode. Besides the positive control, sinomenine (IC50=113 mu M) and bulleyaconitine A (IC50=53 mu M) were found to be potent COX-2 inhibitors. CONCLUSIONS: All the results indicate that the present derivatization quantification method of PGE(2) could be used as the detection method of COX-2 enzyme activity and as the screening method for COX-2 inhibitors. Copyright (C) 2014 John Wiley & Sons, Ltd.