A total of 35 new quinazolinone derivatives bearing the 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole scaffold and the 4-piperidinyl linker were designed, prepared, and assessed for their antibacterial and antifungal activities. Among these derivatives, the chemical structure of compound F5 was clearly verified via single-crystal X-ray diffraction analysis. The experimental results revealed that some of the compounds displayed good even excellent inhibitory effects toward the tested phytopathogenic bacteria. For instance, compound F33 was capable of strongly inhibiting Xanthomonas oryzae pv. oryzae (Xoo) in vitro with an EC₅₀ (half-maximal effective concentration) value of 4.1 μg/mL, about 16-fold more effective than the commercialized bactericide bismerthiazol. Significantly, this compound also effectively suppressed the proliferation of Xoo in the potted rice plants, showing a good in vivo protection efficacy of 47.6% at 200 μg/mL. Subsequently, the antibacterial mechanisms of compound F33 were explored by means of different biophysical and biochemical methods. Last, some of the compounds were found to possess relatively good antifungal activities in vitro, like compound F19 against Phytophthora nicotianae (with an inhibition rate of 67.2% at 50 μg/mL). In a word, the current experimental results imply that the 4-piperidinyl-bridged quinazolinone-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole derivatives possess potential as lead compounds for developing more efficient anti-Xoo bactericides.

中文翻译：

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含有 1,2,4-三唑并[3,4-b][1,3,4]噻二唑部分和 4- 的新型 Quinazolin-4(3H)-one 衍生物的合成、X 射线晶体结构和抗菌研究哌啶基接头

设计、制备了总共 35 种带有 1,2,4-三唑并[3,4- b ][1,3,4]噻二唑支架和 4-哌啶基连接基的新型喹唑啉酮衍生物，并评估了它们的抗菌和抗真菌作用活动。在这些衍生物中，化合物F5的化学结构通过单晶X射线衍射分析得到了清晰的验证。实验结果表明，部分化合物对受试植物病原菌表现出良好甚至优异的抑制作用。例如，化合物F33能够强烈抑制米黄单胞菌pv。米曲霉( Xoo ) 体外的 EC ₅₀（半最大有效浓度）值为 4.1 μg/mL，比商品化杀菌剂双甲噻唑有效约 16 倍。值得注意的是，该化合物还有效抑制了盆栽水稻中Xoo的增殖，在 200 μg/mL 浓度下表现出 47.6% 的良好体内保护功效。随后，通过不同的生物物理和生化方法探讨了化合物F33的抗菌机制。最后，部分化合物在体外具有较好的抗真菌活性，如化合物F19对烟草疫霉（50 μg/mL时抑制率为67.2%）。总之，目前的实验结果表明，4-哌啶基桥联喹唑啉酮-1,2,4-三唑并[3,4- b ][1,3,4]噻二唑衍生物具有作为先导化合物开发更高效的先导化合物的潜力。抗Xoo杀菌剂。