Attenuating effect of plumbagin on Chromobacterium violaceum quorum sensing and biofilm formation: an in-vitro and in-silico approach.

The increasing problem of antibiotic resistance over recent decades calls for alternative methods to reduce bacterial pathogenicity. Targeting quorum sensing (QS) is gaining attention as a promising alternative treatment. This study investigates the potential of plumbagin, a natural naphthoquinone derived from Plumbago species, to inhibit quorum sensing and biofilm formation in Chromobacterium violaceum using both in vitro and in silico methods. In vitro assays revealed that sub-minimum inhibitory concentrations of plumbagin significantly suppressed QS-regulated traits compared to controls. These included a reduction in violacein production by up to 40%, exopolysaccharide levels by up to 30%, and swarming motility and biofilm formation, which were reduced by up to 40%. Quantitative real-time PCR analysis demonstrated that plumbagin (at 2.42 μg/ml, corresponding to 1/4th MIC) decreases the expression of key QS genes (with relative fold changes of 0.36 ± 0.06, 0.35 ± 0.06, and 0.18 ± 0.01 for cviI, cviR, and vioA, respectively), indicating interference with bacterial communication pathways. Furthermore, the hemocompatibility assay demonstrated that the plumbagin concentrations used in this study are safe. Complementary in-silico molecular docking and dynamic simulations confirmed stable interactions between plumbagin and the QS regulatory protein CviR, suggesting its plausible mechanism of action. These results highlight plumbagin as a promising anti-QS agent that could be developed into alternative antibacterial therapies.