了解手性农药的立体选择性生物活性对于准确评估其有效性和优化其使用至关重要。异吡拉赞,一种广泛使用的手性SDHI杀菌剂,仅在外消旋水平研究了其抗真菌活性。因此,为了澄清高生物活性的异构体,首次研究了异吡嗪异构体对4种典型植物病原体的立体选择性生物活性。异构体的生物活性等级为反式-1S,4R,9R-(+)-异吡拉赞>顺式-1R,4S,9R-(+)-异吡拉坦>反式-1R,4S,9S-(-)-异吡拉坦>顺式-1S,4R,9S-(-)-异吡拉赞。通过分子对接模拟和实际检测评估SDH活性以确认立体选择性生物活性的原因。结果表明,异吡嗪的立体选择性生物活性在很大程度上取决于每种异构体与SDH泛素结合位点的差异结合能力,位于由铁硫亚基形成的空腔内,细胞色素b560亚基,和细胞色素b小亚基。此外,揭示异吡嗪立体选择性影响菌丝体生长的分子机制,琥珀酸的含量,富马酸,并测量ATP。此外,通过测量外孢子多糖和草酸含量,确定1S,4R,9R-(+)-和1R,4S,9R-()-异吡嗪更强烈地抑制菌核病侵染植物的能力。研究结果为高效异吡嗪杀菌剂的开发提供了必要的数据,并为分析SDHI杀菌剂的对映选择性活性机理提供了方法学参考。
Understanding the stereoselective bioactivity of chiral pesticides is crucial for accurately evaluating their effectiveness and optimizing their use. Isopyrazam, a widely used chiral SDHI fungicide, has been studied for its antifungal activity only at the racemic level. Therefore, to clarify the highly bioactive isomers, the stereoselective bioactivity of isopyrazam isomers against four typical phytopathogens was studied for the first time. The bioactivity ranking of the isomers was trans-1S,4R,9R-(+)-isopyrazam > cis-1R,4S,9R-(+)-isopyrazam > trans-1R,4S,9S-(-)-isopyrazam > cis-1S,4R,9S-(-)-isopyrazam. SDH activity was assessed by molecular docking simulation and actual detection to confirm the reasons for stereoselective bioactivity. The results suggest that the stereoselective bioactivity of isopyrazam is largely dependent on the differential binding ability of each isomer to the SDH ubiquitin-binding site, located within a cavity formed by the iron-sulfur subunit, the cytochrome b560 subunit, and the cytochrome b small subunit. Moreover, to reveal the molecular mechanism of isopyrazam stereoselectively affecting mycelial growth, the contents of succinic acid, fumaric acid, and ATP were measured. Furthermore, by measuring exospore polysaccharides and oxalic acid content, it was determined that 1S,4R,9R-(+)- and 1R,4S,9R-(+)-isopyrazam more strongly inhibited the ability of Sclerotinia sclerotiorum to infect plants. The findings provided essential data for the development of high-efficiency isopyrazam fungicides and offered a methodological reference for analyzing the enantioselective activity mechanism of SDHI fungicides.