Integrated strategy for the screening of cyclooxygenase-2 inhibitors from triterpenoid saponins in Clematis tangutica

INTRODUCTION

Screening of novel cyclooxygenase-2 (COX-2) inhibitors from complex natural products is not an easy task.

OBJECTIVES

To establish an efficient and feasible strategy for screening COX-2 inhibitors from triterpenoid saponins (TPSs) in Clematis tangutica.

METHODS

Taking TPSs in C. tangutica as example, an optimized macroporous resin (MR) method was established for the enrichment of TPSs. High-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOFMS) was performed to establish the phytochemical profiling of TPSs. Molecular docking was performed to predict the ligand-target interactions and discover the active substances. Chemometric techniques were performed to visualize the structure-effect relationships. High-speed countercurrent chromatography and preparative HPLC were performed to prepare the targets. In vitro activity experiment of COX-2 was performed to verify the virtual screening results.

RESULTS

TPSs in C. tangutica were well enriched with the recovery rate of (80.22 ± 2.37)%. Thirty-four kinds of TPSs of oleanane type were deduced by HPLC-QTOFMS. Five TPSs of clematangoside C, clematangoside D, clematangoticoside J, hederoside H₁ , and hederasaponin B showed stronger binding abilities with COX-2. The structure with more sugar groups at C-28 may be more conducive to the combination with COX-2. Targets were prepared with purities all above 98%. The IC₅₀ values of target TPSs were 6.03 ± 0.24, 12.44 ± 0.15, 9.36 ± 0.19, 4.78 ± 0.13, and 2.59 ± 0.11 μmol/L, respectively.

CONCLUSION

The integrated strategy using MR, HPLC-QTOFMS, molecular docking, chemometrics, target preparation, and in vitro verification was feasible for rapidly screening COX-2 inhibitors from TPSs in C. tangutica.