Design, Synthesis And Biological Activity Study Of New Coumarin Fungicides Containing Isopropanolamine Structur

Emerging pesticide-resistant phytopathogenic bacteria have become a stumbling block for the development and use of pesticides.Therefore,it is extremely imperative to excavate some“greener”agrochemicals with novel action mechanism.Fortunately,quorum-sensing blockers,which interfere with production of bacterial virulence,are regarded as a compelling strategy to manage plant disease without resistance.Herein,a series of isopropanolamine-decorated coumarins derivates were designed and synthesized.Their antibacterial activities and quorum-sensing interference potency were investigated.Notably,compound A₅ exhibited the most bioactivity with half-maximal effective concentration(EC₅₀)values of 6.75,3.11,and 8.85 mg L^-1against Xanthomonas oryzae pv.oryzae（Xoo）,X.axonopodis pv.citri（Xac）and Xanthomonas oryzae pv.oryzicola（Xoc）,respectively.Further biochemical studies on pattern strain Xoo revealed that compound A₅could disturb biofilm formation and suppress bacterial virulence factors（such as flagella）.Moreover,compound A₅ was verified to have inhibitory potency on the gene expression levels regulated by quorum sensing.More interestingly,anti-Xoo bioassay in vivo revealed that compound A₅could effectively manage bacterial leaf blight disease,affording with bioactivity including curative activity（53.2%）and protective activity（43.6%）at the dosage of200 mg L^-1.Overall,this study proposed an advisable tactics for development of efficient bactericide candidates to control plant bacterial diseases by interfering with QS.