Rapid screening and identification of monoamine oxidase-A inhibitors from Corydalis Rhizome using enzyme-immobilized magnetic beads based method

Monoamine oxidase-A (MAO-A) is considered an important therapeutic target in depression. In order to rapidly screen and identify novel MAO-A inhibitors from natural products, a magnetic bead (MB) based drug discovery tool was developed in this study. MAO-A was first immobilized onto the surface of MBs, and the resulting MAO-A-immobilized MBs (MAO-A-MBs) were then applied to ligand fishing by combining them with high-performance liquid chromatography (HPLC) coupled with quadrupole time-of-flight tandem mass spectrometry (Q-TOF-MS/MS). The inherent catalytic activity and kinetic parameters of the immobilized-MAO-A were determined by measuring the peak area of the oxidation product. The immobilized MAO-A activity was found to remain over 80% after storage at 4 °C for about 7 days. Seven compounds (tetrahydrocolumbamine, protopine, jatrorrhizine, glaucine, tetrahydropalmatine, palmatine, dehydrocorydaline) with high binding affinity to MAO-A were fished out from the ethyl acetate fraction extract of Corydalis Rhizome . Their MAO-A inhibitory activity was further verified by enzymatic inhibition assay. These results show that the developed approach using MAO-A-MBs combined with HPLC-Q-TOF-MS/MS is suitable for the fast screening and identification of MAO-A inhibitors in complex mixtures.