Antimicrobial effects of new designed 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives against some pathogenic microbial strains

Chromenes, also called benzopyrane derivatives and chromene-4-one, are natural compounds which have several biological effects. The aims of the present study were to synthesize 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives and to evaluate their antibacterial effects against selected bacterial strains. Nine 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives were designed and synthesized. Each synthesized derivative was dissolved in dimethyl sulfoxide and diluted using distilled water. Then, serial dilutions of 64, 32, 16, 8, 4, 2, 1, 0.5, 0.25, and 0.125 μg/ml were prepared and added to the Mueller-Hinton agar medium. The minimum inhibitory concentration (MIC) of derivatives was determined against routine pathological strains of bacteria including Staphylococcus epidermidis, Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, Serratia marcescens, Pseudomonas aeruginosa, and Klebsiella pneumoniae on the basis of growth on the each plate. Only two compounds of 2-amino-5,6,6,1-tetrahydro-5-oxo-4-(3-pyridinyl)-4H-chromene-3-carbonitrile and 2-amino-5,6,6,1-tetrahydro-6,6-dimethyl-5-oxo-4-(3-pyridinyl)-4H-chromene-3-carbonitrile showed antibacterial activity especially against M. luteus and B. subtilis. Some of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives had stronger antibacterial effects which may be due to substituted pyridine ring. Therefore, these compounds are a candidate as the new choices of antibacterial drugs.