Inhibitory activity and mechanism of aryl furan thioesters containing 1,3,4-thiadiazole against Erwinia amylovora.

The Gram-negative bacterium Erwinia amylovora induces fire blight disease in Rosaceae hosts, severely damaging pome fruit trees including pear, apple, and hawthorn cultivars. Traditional control methods, such as antibiotics and copper-based agents, are associated with plant damage and the emergence of resistant bacterial strains, and present significant challenges. This study aims to design and synthesize a novel eco-friendly bactericide. In this study, we designed and synthesized 30 small-molecule compounds by combining 1,3,4-thiadiazole, a key moiety of zinc thiazole, with 5-phenyl-2-furan. Structural characterization of these compounds was performed using 1H and 13C NMR spectroscopy, complemented by elemental composition analysis. Compound II-10 was identified as the most promising compound in initial screenings, with a median effective concentration (EC50) of 9.04 μg/mL. Inoculation experiments demonstrated that at a concentration of 200 μg/mL, II-10 effectively inhibited E. amylovora and controlled pear fire blight, with its protective activity exceeding its curative effects. Furthermore, fluorescence microscopy, flow cytometry and scanning electron microscopy analysis revealed a potential mechanism of antimicrobial action involving reactive oxygen species generation, apoptosis and changes in bacterial morphology. Toxicity assessment showed that II-10 was non-toxic to zebrafish, earthworm and silkworm. This study established that II-10 was a lead scaffold for the development to control pear fire blight, providing theoretical support for optimizing small-molecule compounds.