Paper
Synthesis, antioxidant, and antimicrobial activities of new 2-(1,5,6-trimethyl-1H-benzo[d]imidazole-2-carbonyl)-2,3-dihydro-1H-pyrazole-4-carbonitriles, (1,3,4-oxadiazol-2-yl)-1H-benzo[d]imidazol-5-yl)(phenyl)methanones, and (1,3,4-oxadiazol-2-yl)-1,5-dihydro-[1,2,4]triazolo[1,5-a]pyridine-8-carboni
Published Dec 1, 2012 · F. Bassyouni, H. A. Tawfik, A. Hamed
Egyptian Pharmaceutical Journal
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Abstract
Objectives A new series of 2-(1,5,6-trimethyl-1H-benzo[d]imidazole-2-carbonyl)-2,3-dihydro-1H-pyrazole-4-carbonitrile ( 6a , b ), (1,3,4-oxadiazol-2-yl)-1H-benzo[d]imidazol-5-yl)(phenyl) methanone ( 9 – 11 ), and (1,3,4-oxadiazol-2-yl)-1,5-dihydro-[1,2,4]triazolo[1,5- a ]pyridine-8-carbonitrile ( 14 – 16 ) derivatives were synthesized and evaluated for their antioxidant and antimicrobial activities; in addition, their quantitative structure–activity relationships and molecular docking were investigated. Methods The target compounds 6a , b were synthesized by the following method: reaction of 5,6-dimethyl-1H-benzoimidazole-2-carbohydrazide ( 2 ) with 4-(dimethyl amino)benzaldehyde or anthracene-9-carbaldehyde yielded Schiff’s bases 3a , b , which were reacted with ethyl cyanoacetate to yield 1H-pyrazole-4-carbonitriles 4a , b ; N -methylation of 4a , b afforded 5a , b , which reacted with 4-aminoantipyrine to give 6a , b . In addition, 5-benzoyl-1H-benzo[d]imidazole-2-carbohydrazide ( 8 ) or 8-cyano-6-isocyano-5-oxo-7-phenyl-1,5-dihydro-[1,2,4]triazolo[1,5- a ]pyridine-2-carbohydrazide ( 13 ) reacted with different carboxylic acids such as crotonic acid, 3,4-diaminobenzoic acid, and 6-hydroxy-4-methoxybenzofuran-5-carboxylic acid to form compounds 9 – 11 and 14 – 16 , respectively. The synthesized compounds were evaluated for their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, and the diffusion plate method for antimicrobial activity. Results and conclusion Among other tested compounds, compounds 15 , 11 , and 10 possessed the highest antioxidant activity, whereas compounds 4a , 5b , 6b , 10 , and 11 displayed high activity against Staphylococcus aureus , Salmonella typhimurium , and Candida albicans . The quantitative structure–activity relationships of the studied compounds 4a , 4b , 5b , 6b , 10 , 11 , 14 , 15 , and 16 indicated a high correlation ( r 2 =0.82) between the predicted and actual activities as obtained from molecular descriptors and the inhibitory activity of this set of tested molecules measured as antioxidant activity. Moreover, the three-dimensional (3D) pharmacophore was generated, and docking of the most active antibacterial compound 4a against the dihydropteroate synthase enzyme gave comparable scores for hydrogen bond interaction (−13.5 kcal/mol) and binding mode to the reference antibiotic sulfamethoxazole (−13.00 kcal/mol).
New compounds synthesized from 2-(1,5,6-trimethyl-1H-benzo[d]imidazole-2-carbonyl)-2,3-dihydro-1H-pyrazole-4-carbonitriles show promising antioxidant and antimicrobial properties.
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