Quorum sensing inhibition activity of garlic extract and p-coumaric acid

Aims: The goal of this work was to investigate the influence of DMSO, garlic extract and p-coumaric acid on bacterial quorum sensing (QS). Methods and Results: The decreases in the QS responses of QS reporter strains Escherichia coli pSB401 and pSB536, Agrobacterium tumefaciens NTL4, Chromobacterium violaceum 5999 and wt 494, Pseudomonas putida IsoF/gfp and environmental Pseudomonas chlororaphis were quantified in relation to growth inhibitory effects. DMSO showed no significant QS-specific effects on the strains tested even at close-to-lethal concentrations. Garlic extracts antagonized the activity of QS receptors LuxR, AhyR and TraR, but were toxic at higher concentrations. P-coumaric acid fully inhibited QS responses of 5999, NTL4 and P. chlororaphis, with no influence on cell viability. Conclusions: The quorum sensing inhibition activity of garlic was extended to novel receptors, and p-coumaric acid was found to possess previously undescribed QS antagonist properties. Significance and Impact of the Study: The results suggest that p-coumaric acid might act as QS inhibitor. Further studies are required to understand its role in the regulation of QS and investigate structurally related compounds.