Ligand fishing and identification of acetylcholinesterase inhibitors in Mahonia bealei (Fort.) Carr. using high performance liquid chromatography-mass spectrometry

Abstract

A fishing platform was developed using immobilized capillary enzyme reactors in combination with liquid chromatography-mass spectrometry (LC-MS) to fish acetylcholinesterase inhibitor (AChEI) from Mahonia bealei (Fort.) Carr. (M. bealei) extract. Four potential AChEIs (columbamine, jatrorrhizine, berberine, and palmatine) were successfully screened out and identified. Their AChE inhibitory activities were further verified by an in vitro assay with IC50 values of 0.93 ± 0.12 μg/mL (columbamine), 3.50 ± 0.15 μg/mL (jatrorrhizine), 2.51 ± 0.12 μg/mL (berberine), and 1.52 ± 0.13 μg/mL (palmatine). A synergy study of these AChEIs was subsequently investigated. In comparison with the IC50 value of M. bealei extract (IC50=0.83 ± 0.21 μg/mL), it can be stated that M. bealei extract is much more active than any single AChEI. Thereafter, the determination of these four alkaloids were investigated and AChE inhibitory effect were compared in terms of the extract and corresponding contents of these four alkaloids. The inhibitory effects of extract at each concentration were stronger than four alkaloids mixture. The results demonstrated that not the four AChEI mixture cause the synergistic effect but rather than the concentrations or ratios of these AChEIs play a vital role in their synergy study.