Synthesis and antagonistic evaluation of fluorinated imidazolium salt [1-(2,6-diisopropylphenyl)-3-(2-fluoro-benzyl)-1H-imidazol-3-ium bromide] against significant phytopathogens in agriculture

The current investigation evaluated the in vitro bioefficacy of a newly synthesized unsymmetrical imidazolium salt [1-(2,6-diisopropylphenyl)-3-(2-fluoro-benzyl)-1H-imidazol-3-ium bromide] that contains the electron- withdrawing fluorine atom at the ortho position against agriculturally significant phytopathogens. The molec ular structure of the imidazolium salt was characterized by various spectroscopic techniques such as 1H, 13C, and 19F NMR, FTIR, and high-resolution mass spectrometry (HRMS). Antimicrobial bioassay of the compound has been tested against two Gram-negative, bacterial phytopathogens namely Ralstonia solanacearum (Rs) (Gen Bank accession no. OQ743450) [causal agent: bacterial wilt of solanaceous crops], and Xanthomonas citri pv. citri (Xcc) (Gen Bank accession no. OR7036310) [causal agent: citrus canker in citrus trees] and two fungal phytopathogens namely Fusarium solani (Gen Bank accession no. OR140825) [causal agent: Fusarium die-back in tea] and Pseudopestalotiopsis chinensis (Gen Bank accession no. OR140826) [causal agent: grey blight in tea]. Different concentrations of imidazolium salt was tested against the target phytopathogens using the in vitro antimicrobial bioassay through disc diffusion method. The imidazolium salt demonstrated a maximum percentage inhibition of 16.70 and 21.78 against the bacterial phytopathogens R. solanacearum, and X. citri pv. citri, respectively, at a concentration of 2000 ppm over negative control. Similarly, the compound demonstrated promising antagonism against the tea fungal pathogens F. solani and P. chinensis (percentage inhibition up to 61.43 and 80.84, respectively at 2000 ppm) over negative control. Five replications were maintained in each of the cases. The present investigation demonstrated the potential of fluorinated imidazolium salt as commercial antimicrobial agent in integrated disease management schedule to control significant phytopathogenesis in agriculture including in tea.本研究评估了一种新合成的不对称咪唑鎓盐[1-(2,6-二异丙基苯基)-3-(2-氟苄基)-1H-咪唑-3-鎓溴盐]的体外生物活性，该盐在邻位带有吸电子氟原子，可对抗农业重要植物病原菌。该咪唑鎓盐的分子结构通过¹H、¹³C、¹⁹F核磁共振波谱（NMR）、傅里叶变换红外光谱（FTIR）以及高分辨质谱（HRMS）等多种波谱技术进行了表征。本研究针对两种革兰氏阴性细菌性植物病原菌——青枯劳尔氏菌（Ralstonia solanacearum，Rs，GenBank登录号：OQ743450，其为茄科作物青枯病的致病菌）以及柑橘黄单胞菌柑橘致病变种（Xanthomonas citri pv. citri，Xcc，GenBank登录号：OR7036310，其为柑橘树柑橘溃疡病的致病菌），还有两种真菌性植物病原菌——茄病镰刀菌（Fusarium solani，GenBank登录号：OR140825，其为茶树茄病枯萎病的致病菌）以及中国拟盘多毛孢（Pseudopestalotiopsis chinensis，GenBank登录号：OR140826，其为茶树灰斑病的致病菌），对该化合物开展了抗菌生物活性测定。采用纸片扩散法的体外抗菌生物测定法，测试了不同浓度的该咪唑鎓盐对目标植物病原菌的抑制效果。在2000 ppm浓度下，相较于阴性对照组，该咪唑鎓盐对细菌性植物病原菌青枯劳尔氏菌和柑橘黄单胞菌柑橘致病变种的最大抑菌率分别为16.70%和21.78%。同样，相较于阴性对照组，该化合物对茶树真菌病原菌茄病镰刀菌和中国拟盘多毛孢表现出良好的拮抗活性，在2000 ppm浓度下的抑菌率分别可达61.43%和80.84%。所有实验均设置5次生物学重复。本研究表明，含氟咪唑鎓盐具备作为商用抗菌剂应用于综合病害防控方案的潜力，可用于防治包括茶树病害在内的多种农业重要植物病害。