Flavonoids as quorum sensing inhibitors: A promising strategy to fight against bacteria

Abstract

Bacterial biofilms are an increasing concern in several areas: in clinics, they cause up to a 1000-fold increase in bacterial antibiotic resistance; in industry, they are a cause of clogging and operative problems; environmentally, they are a first stage in biofouling. Bacterial biofilm formation relies on a process of chemical communication between bacterial cells called quorum sensing (QS) [1]. Since QS blockers do not target bacterial growth, they do not exert a selective pressure on bacterial populations and consequently, they have emerged as a promising alternative to antibiotic and biocidal treatments. Natural products are a major source of chemical diversity and have provided important therapeutic agents for many bacterial diseases [2]. In that context, flavonoids, a family of plant-derived compounds, have been revealed as potential inhibitors of biofilm formation and the production of virulence factors in the pathogenic bacteria by interfering with QS mechanisms [3]. In the present study, nine flavonoids, including seven chalcones and two flavanones, isolated from Piper delineatum (Piperaceaea) and Renealmia alpinia (Zingiberaceae) were screened for their capacity to reduce the production of violacein, a QS-regulated phenotype, in the reporter strain Chromobacterium violaceum CV026. Several compounds exhibited significant QS inhibitory activities. Particularly, a compound of this series exhibited a very promising profile in the µM range. Given that the activities of this family of compounds have been reported at the mM level [4], further studies are in course to characterise the bioactive potential of this molecule.