Antibiotic resistance is a growing threat worldwide, causing serious problems in the treatment of microbial infections. The
discovery and development of new drugs is urgently needed to overcome this problem which has greatly undermined the clinical
effectiveness of conventional antibiotics. An intricate cell-cell communication system termed quorum sensing (QS) and the
coordinated multicellular behaviour of biofilm formation have both been identified as promising targets for the treatment and
clinical management of microbial infections. QS systems allow bacteria to adapt rapidly to harsh conditions, and are known to
promote the formation of antibiotic tolerant biofilm communities. It is well known that biofilm is a recalcitrant mode of growth
and it also increases bacterial resistance to conventional antibiotics. The pharmacological properties of coumarins have been well
described, and these have included several that possess antimicrobial properties. More recently, reports have highlighted the
potential role of coumarins as alternative therapeutic strategies based on their ability to block the QS signalling systems and to
inhibit the formation of biofilms in clinically relevant pathogens. In addition to human infections, coumarins have also been
found to be effective in controlling plant pathogens, infections in aquaculture, food spoilage and in reducing biofouling caused by
eukaryotic organisms. Thus, the coumarin class of small molecule natural product are emerging as a promising strategy to combat
bacterial infections in the new era of antimicrobial resistance
