Quaternary ammonium and amido derivatives of pyranochromenones and chromenones: synthesis and antimicrobial activity evaluation

Infectious diseases and the development of their resistance to antimicrobial agents are alarming issues worldwide and consistent efforts are being made to develop efficient antimicrobial agents. In this perspective, a series of novel ammonium and amide derivatives of pyranocoumarin and coumarin were synthesized and evaluated for their antimicrobial activity. Among them, six compounds exhibited significant activity against gram-positive bacteria Bacillus cereus (MTCC 430) and Bacillus subtilis (MTCC 121) and a gram-negative bacterium Pseudomonas aeruginosa (MTCC 741). The compound N,N,N-triethyl-10-(4,8,8-trimethyl-2-oxo-2,6,7,8-tetrahydropyrano[3,2-g]chromen-10-yloxy)decan-1-aminium bromide (16) exhibited the highest antibacterial activity with MIC value of 5 μg/ml in MDA. Compounds 17 and 18 exhibited modest antifungal activity with MIC of 6.25 μg/ml against Trichophyton rubrum (clinical isolate) in MDA. Haemolytic assay results demonstrated that three out of six compounds were safe at their respective MIC values. These results provide insights for further optimization of the scaffolds for designing the next generation of compounds as lead antimicrobial agents.