Monoamine oxidase inhibitory activity of 2-aryl-4H-chromen-4-ones.

A series of twenty 2-aryl-4H-chromen-4-one (flavones) derivatives (3a-3s) were synthesized and tested for hMAO inhibitory activity. Fifteen compounds (3a, 3c, 3e-3h, 3j-3p, 3r, 3s) were found to be selective towards MAO-B, while 3d was selective towards MAO-A, and 3b, 3i and 3q were non-selective. Experimental Selectivity Index for MAO-B ranges from 2.0 (3g, 3p) to 30.0 (3j). Compound 3j, which is carrying 3,4-di-OMeC6H3 groups at R position on the molecule, was found to be potent MAO-B inhibitor amongst the fifteen with Ki value for MAO-B of 0.16±0.01 µM comparable to that of standard drug, Selegiline (Ki for MAO-B is 0.16±0.01 µM). Compound 3j also appeared as the most selective MAO-B inhibitor according to its best selectivity index (30.0), which is comparable to that of Selegiline (SIMAO-B=35.0). Molecular docking and molecular dynamics simulation studies were carried out using Autodock-4.0 and Amber12 to understand the molecular level interaction and energy relation of MAO isoforms with selective inhibitors (3d and 3j). Simulation results are in good agreement with the experimental results. Leads identified may further be explored to develop potent isoform specific inhibitors of MAO.

Monoamine oxidase inhibitory activity of 3,5-biaryl-4,5-dihydro-1H-pyrazole-1-carboxylate derivatives.

Ethyl and phenyl carbamate derivatives of pyrazoline (3a-3h) were synthesized and tested for their MAO inhibitory activity. All the compounds were found to be selective towards MAO-A. Phenyl carbamates (3e-3h) were better than ethyl carbamates (3a-3d) and displayed the best selectivity index. Compound 3f (KiMAO-A; 4.96 ± 0.21 nM) was found to be equally potent as that of standard drug, Moclobemide (KiMAO-A; 5.01 ± 0.13 nM) but with best selectivity index (8.86 × 10(-5)). Molecular docking studies with R &S conformer of 3f revealed S-enantiomer is better than R-enantiomer as reported earlier by other groups. It is proposed that VdW's radii of the substitution (bulkiness) in ring B determine the potency of phenyl carbamates.

Monoamine oxidase inhibitory activities of novel 3,4-dihydroquinolin-(1H)-2-one derivatives.

Three 3,4-dihydroquinoline-(1H)-2-one derivatives were synthesized and their monoamine oxidase (MAO) inhibitory activities were evaluated. The calculated IC(50) values revealed that compound Q (N-amino-3,4-dihydroquinoline-(1H)-2-one), which carries a free amine group in the molecule, inhibited rat liver MAO-B competitively and reversibly suggesting that this relatively small compound may interact with the active site channel of the enzyme while the compounds QB (1-(benzlyden-amino)-3,4-dihydroquinoline-(1H)-2-one), PCN (2-(3-cyano-2-oxo-4-phenyl-2H-quinolin-1-yl-N-cyclohexyl-2-(4'-chlorophenyl) acetamide) and MG (tert-butyl-N-[cyclohexylcarbamoyl-(3-hydroxyphenyl)methyl]-N-(2-benzoylphenyl)-carbamate) inhibited rat liver MAO-B non-competitively and irreversibly, suggesting that these compounds may interact with another hydrophobic binding region outside of the active site of the enzyme.

Interaction of rat lung SSAO with the novel 1-N-substituted thiocarbamoyl-3-substituted phenyl-5-(2-pyrolyl)-2-pyrazoline derivatives.

Interactions of twelve new synthesized 1-N-substituted thiocarbamoyl-3-substituted phenyl-5-pyrolyl-2-pyrazoline derivatives with rat lung semicarbazide-sensitive amine oxidase (SSAO) were assessed. Pyrazoline derivatives were synthesized according to previous methods and SSAO was purified from the crude microsomal fractions of rat lung.Three compounds (3e, 3f, 3k) with a p-methoxy group at the phenyl ring inhibited rat lung SSAO non-competitively and irreversibly, and showed higher affinity towards SSAO when expressed in terms of IC(50) for SSAO/Monoamine oxidase B (MAO-B). Since these novel pyrazoline derivatives have been found to act as suicide inhibitors of SSAO, the semicarbazide group in these molecules may be responsible for the SSAO inhibitory action. It is suggested that these compounds cannot enter the first small active site cavity of SSAO and may interact tightly with another binding site or with some other reactive groups present in the molecule. Compound 3e showed the highest inhibitory activity on rat lung SSAO. The novel pyrazoline derivatives may be used to discriminate between Cu- and FAD-containing amine oxidases and may have promising features as anti-Parkinson agents if the SSAO-inhibitory effects can be supported by in vivo studies.