Benzo[d]thiazole-2-thiol bearing 2-oxo-2-substituted-phenylethan-1-yl as potent selectivelasBquorum sensing inhibitors of Gram-negative bacteria

Abstract

Quorum sensing is a well-known term for describing bacterial cell-cell communication. Bacteria use quorum sensing pathways to respond to external factors such as nutrient availability, defense mechanisms, and coordinate host toxic behaviors such as biofilm formation, virulence production, and other pathogenesis. Discovery of novel compounds which inhibit quorum sensing without being antibiotic are currently emerging fields. Herein, the library of fifteen benzo[d]thiazole/quinoline-2-thiol bearing 2-oxo-2-substituted-phenylethan-1-yl compounds was designed, synthesized and evaluated to find novel quorum sensing inhibitors. Firstly, compounds were evaluated for their growth inhibitory activities at high concentrations up to 1000 μg mL−1towardPseudomonas aeruginosa. Under our conditions, twelve compounds showed moderate growth inhibitory activities in the concentration tested. To our delight, three compounds3,6and7do not affect the growth of the bacteria which were chosen for the evaluation of quorum sensing inhibitor activities. In theLasBsystem, our compounds3,6,7showed promising quorum-sensing inhibitors with IC50of 115.2 μg mL−1, 182.2 μg mL−1and 45.5 μg mL−1, respectively. In thePqsRsystem, no activity observed suggesting that the selectivity of the compound toward theLasBsystem. In addition,7showed the moderate anti-biofilm formation ofPseudomonas aeruginosa. Docking studies revealed that3,6and7binding to the active site ofPseudomonas aeruginosaquorum sensingLasRsystem with better affinity compared to reference compounds4-NPO. Finally, computation calculations suggest that compounds are a good template for further drug development.