Functionalized magnetic nanoparticles coupled with mass spectrometry for screening and identification of cyclooxygenase-1 inhibitors from natural products.

Development of simple and effective methods for high-throughput, high-fidelity screening and identification of cyclooxygenase-1 (COX-1) inhibitors from natural products are important for drug discovery to treat inflammation and carcinogenesis. Here, we developed a new screening assay based on cyclooxygenase-1 (COX-1) functionalized magnetic nanoparticles (i.e. Fe3O4@SiO2-COX-1) for solid phase ligand fishing, and then mass spectrometry (MS) was applied for structural identification. Incubation conditions were optimized. High specificity for isolating COX-1 inhibitors was achieved by testing positive control, indomethacin, with active and inactive COX-1. Moreover, high stability of immobilized COX-1 (remained 95.3% after ten consecutive cycles) allows the analysis reproducible. When applied to turmeric extract, four curcuminoids (i.e. curcumin, demethoxycurcumin, bisdemethoxycurcumin, and 1-(4-hydroxy-3,5-dimethoxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)-(1E,6E)-1,6-heptadiene-3,5-dione), difficult to be distinguished from original MS spectrum of turmeric extract, were isolated as main COX-1 inhibitors. Their structures were characterized based on their accurate molecular weight and diagnostic fragment ions. The results indicated that the proposed method was a simple, robust and reproducible approach for the discovery of COX-1 inhibitors from complex matrixes.