Inhibition of monoamine oxidases by benzimidazole chalcone derivatives

Ten benzimidazole chalcone derivatives were synthesized, and their monoamine oxidase (MAO) inhibitory activity was evaluated. Most compounds showed higher inhibitory activity against MAO-B than MAO-A. Compound BCH2 exhibited an IC₅₀ value of 0.80 μM, thereby showing the most potent inhibition amongst all. In addition, BCH2 showed the highest MAO-B selectivity index (SI) with an SI value of 44.11 compared to MAO-A. Among the substituents, the halogen group showed the best MAO-B inhibition, and the ortho-position of the B ring showed better inhibitory activity than the para-site. In comparison with ortho-substituents, the inhibitory activity increased in the order, -Cl > -Br > -F > -H. BCH2 was found to be a competitive inhibitor of the enzyme with optimum inhibition kinetics, where K_i was found to be 0.25 ± 0.014 μM. In the reversibility experiment, BCH2 showed a recovery pattern after MAO-B inhibition, similar to that of lazabemide. Thus, BCH2 is a potent, reversible, and selective MAO-B inhibitor and has been suggested as a candidate for the treatment of neurological disorders.