Discovery and evaluation of 3-(2-isocyanobenzyl)-1-indole derivatives as potential quorum sensing inhibitors for the control of infections .

Quorum sensing (QS) inhibition stands out as an innovative therapeutic strategy for combating infections caused by drug-resistant pathogens. In this study, we assessed the potential of 3-(2-isocyanobenzyl)-1-indole derivatives as novel quorum sensing inhibitors (QSIs). Initial screenings of their QS inhibitory activities were conducted against PAO1 and CV026. Notably, six 3-(2-isocyanobenzyl)-1-indole derivatives (4, 12, 25, 28, 32, and 33) exhibited promising QS, biofilms, and pyocyanin inhibitory activities under minimum inhibitory concentrations (MICs) against PAO1. Among them, 3-(2-isocyano-6-methylbenzyl)-1-indole (IMBI, 32) emerged as the most promising candidate, demonstrating superior biofilm and pyocyanin inhibition. Further comprehensive studies revealed that derivative 32 at 25 μg mL inhibited biofilm formation by 70% against PAO1, as confirmed by scanning electron microscopy (SEM). Additionally, derivative 32 substantially increased the susceptibility of mature biofilms, leading to a 57% destruction of biofilm architecture. In terms of interfering with virulence factors in PAO1, derivative 32 (25 μg mL) displayed remarkable inhibitory effects on pyocyanin, protease, and extracellular polysaccharides (EPS) by 73%, 51%, and 37%, respectively, exceeding the positive control resveratrol (RSV). Derivative 32 at 25 μg mL also exhibited effective inhibition of swimming and swarming motilities. Moreover, it downregulated the expressions of QS-related genes, including , , , , , , , , and , by 1.82- to 10.87-fold. Molecular docking, molecular dynamics simulations (MD), and energy calculations further supported the stable binding of 32 to LasR, RhlI, RhlR, EsaL, and PqsR antagonizing the expression of QS-linked traits. Evaluation of the toxicity of derivative 32 on HEK293T cells CCK-8 assay demonstrated low cytotoxicity. Overall, this study underscores the efficacy of derivative 32 in inhibiting virulence factors in . Derivative 32 emerges as a potential QSI for controlling PAO1 infections and an anti-biofilm agent for restoring or enhancing drug sensitivity in drug-resistant pathogens.