Novel Benzothiazole Derivatives as Potential Anti-Quorum Sensing Agents for Managing Plant Bacterial Diseases: Synthesis, Antibacterial Activity Assessment, and SAR Study

Abstract

As quorum sensing (QS) regulates bacterial pathogenicity, antiquorum sensing agents have powerful application potential for controlling bacterial infections and overcoming pesticide/drug resistance. Identifying anti-QS agents thus represents a promising approach in agrochemical development. In this study, the anti-QS potency of 53 newly prepared benzothiazole derivatives containing an isopropanolamine moiety was analyzed, and structure-activity relationships were examined. Compound <b>D</b>_<b>3</b> exhibited the strongest antibacterial activity, with an <i>in vitro</i> EC₅₀ of 1.54 μg mL^-1 against <i>Xanthomonas oryzae</i> pv <i>oryzae</i> (<i>Xoo</i>). Compound <b>D</b>_<b>3</b> suppressed QS-regulated virulence factors (e.g., biofilm, extracellular polysaccharides, extracellular enzymes, and flagella) to inhibit bacterial infection. <i>In vivo</i> anti-<i>Xoo</i> assays indicated good control efficiency (curative activity, 47.8%; protective activity, 48.7%) at 200 μg mL^-1. Greater control efficiency was achieved with addition of 0.1% organic silicone or orange peel essential oil. The remarkable anti-QS potency of these benzothiazole derivatives could facilitate further novel bactericidal compound development.