Antimicrobial activities of pyridinium-tailored pyrazoles bearing 1,3,4-oxadiazole scaffolds

Herein, a series of pyridinium-tailored 5-trifluoromethylpyrazoles containing 1,3,4-oxadiazole moieties were constructed through coupling key pharmaceutical fragments of pyridinium, pyrazole, and 1,3,4-oxadiazole scaffolds in single molecular architecture. Antimicrobial results suggested that this kind of compounds exhibited significant activities against three types of pathogenic bacteria and six fungal strains in vitro. The minimal EC50 values of designed compounds against Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Xanthomonas axonopodis pv. citri could reach to 0.467, 1.04, and 0.600 μg/mL, respectively, through tuning and optimizing N-substituents, bridging atom, and alkyl length of the tailor. Antifungal assays revealed that all title molecules possessed considerable activity against Botrytis cinerea with the minimal EC50 value up to 2.71 μg/mL; and compounds I-8, I-10, I-12, II-12, and IV-12 showed the strongest growth suppression toward Rhizoctonia solani with EC50 values ranging from 10.2 to 24.0 μg/mL. Given the above results, this kind of compounds could serve as new lead compounds in the research of antimicrobial chemotherapy.