Novel Class of Chalcone Oxime Ethers as Potent Monoamine Oxidase-B and Acetylcholinesterase Inhibitors

Previously synthesized novel chalcone oxime ethers (COEs) were evaluated for inhibitory activities against monoamine oxidases (MAOs) and acetylcholinesterase (AChE). Twenty-two of the 24 COEs synthesized, except and , had potent and/or significant selective inhibitory effects on MAO-B. potently inhibited MAO-B with an IC value of 0.018 µM, which was 105, 2.3, and 1.1 times more potent than clorgyline, lazabemide, and pargyline (reference drugs), respectively. , and were also active against MAO-B, both had an IC value of 0.028 µM, which was 67 and 1.5 times lower than those of clorgyline and lazabemide, respectively. Most of the COEs exhibited weak inhibitory effects on MAO-A and AChE. most potently inhibited MAO-A (IC = 0.88 µM) and also significantly inhibited MAO-B (IC = 0.13 µM), and it could be considered as a potential nonselective MAO inhibitor. and inhibited AChE with IC values of 5.35 and 4.39 µM, respectively. The selectivity index (SI) of for MAO-B was higher than that of (SI = 778.6 vs. 222.2), but the IC value (0.028 µM) was slightly lower than that of (0.018 µM). In reversibility experiments, inhibitions of MAO-B by and were recovered to the levels of reference reversible inhibitors and both competitively inhibited MAO-B, with K values of 0.0075 and 0.010 µM, respectively. Our results show that and are potent, selective MAO-B inhibitors, and is a candidate of dual-targeting molecule for MAO-B and AChE.