Monoamine oxidase inhibitory activity of methoxy-substituted chalcones

The MAO-B inhibitory activity of chalcone (1, 3- diphenyl-2-propen-1-one) based compounds arise from its structural similarity with 1, 4-diphenyl-2-butene, a known MAO-B inhibitor. Based on our previous report, the methoxy-substituted with fluorine containing chalcones are promising reversible MAO-B inhibitors, while in the present study, a series of methoxylated chalcones (C1-C9) bearing substitution on the para position of ring B was synthesized and evaluated for their human monoamine oxidase inhibitory activity. With the exception of (2E)-1-(4-methoxyphenyl)-3-(4-nitrophenyl) prop-2-en-1-one (C7), which is a nonselective inhibitor, the chalcones exhibited competitive, selective, and reversible inhibition of hMAO-B. The most potent compound, (2E)-3-[4-(dimethylamino) phenyl]-1-(4-methoxyphenyl) prop-2-en-1-one (C5), showed the best inhibitory activity towards hMAO-B (IC₅₀=0.29±0.011μM;K_i=0.14±0.001μM). The reversibility of MAO-B inhibition by compound C5 was demonstrated by the recovery of enzyme activity after dialysis of mixtures containing enzyme and inhibitor. The reversiblity of C5 was 25.38±1.40 and 92.00±3.87% before and after dialysis, respectively. PAMPA was carried out to evaluate the blood-brain barrier effects of the designated compounds. Moreover, the most potent MAO-B inhibitor, C5, was found to be nontoxic towards cultured hepatic cells at 5 and 25μM, with 97 and 90% viability. Molecular docking study was performed against hMAO-B to observe the binding site interactions of the lead compound.