A small library of 4-(alkylamino)-3-nitrocoumarin derivatives with potent antimicrobial activity against gastrointestinal pathogens

Abstract

Due to a confirmed antimicrobial activity of both natural and synthetic coumarin derivatives, the present study was envisaged to provide a further insight into the antimicrobial potential of coumarins through a screening of a designed library of nine 4-(alkylamino)-3-nitrocoumarins against a panel of 24 laboratory strains and resistant (isolates) bacterial and fungal pathogens. All compounds showed some degree of strain-selective activity, that was, in some cases, very pronounced, reaching the value of 0.04 nmol/ml (i.e. 12 ng/ml) for the minimal inhibitory concentration against Candida albicans. The observed activity was higher against Gram-negative strains, among which the most susceptible strain, among both ATCC strains and clinical isolates, was Salmonella enteritidis. These results point out to a high potential of these coumarins as antimicrobials for the treatment of gastrointestinal and other infections caused by highly resistant microbial strains. Finally, a multivariate statistical analysis of the herein obtained and previous results on the antimicrobial activity of related selected coumarins was performed to allow an easier structure-activity discussion.