Synthesis and Preliminary Antifungal Evaluation of Acetylated Glucopyranoside Amidrazones against Pythium aphanidermatum , Rhizoctonia solani and Fusarium solani in Cucumber

Soilborne damping-off caused by Pythium aphanidermatum, Rhizoctonia solani, and Fusarium solani remains a major constraint to cucumber production and shows the need for new chemistries with tractable safety profiles. We synthesized and characterized eight acetylated glucopyranoside amidrazones (AM 1–AM 8) and conducted a preliminary antifungal screen. In dual-culture assays on PDA, halogenated analogues (AM 2:4Br; AM 6:3,5Cl2; AM 7:3Cl) produced the largest inhibition zones against R. solani and F. solani, whereas P. aphanidermatum was less responsive. Scanning electron microscopy revealed wrinkled, shrunken, and fragmented hyphae at the treatment front, and bulk electrolyte leakage increased with concentration and time, which is consistent with the loss of membrane integrity as a contributing mode of action. In a greenhouse seedling screen, AM 2 and AM 7 increased survival to ∼60–67% in Fusarium- and Rhizoctonia-infested soil (vs 0% in inoculated controls), while responses to Pythium were lower; compound-only pots showed 70–90% survival, and AM 6 produced shorter, yellowish seedlings, indicating a potential phytotoxicity signal at the tested rate that warrants dose optimization. This first-round evaluation did not include commercial fungicide comparators or EC50 determinations; therefore, we frame these amidrazones as lead scaffolds. We outline in the methods how potency benchmarking (poisoned-agar EC50 vs reference fungicides) and crop-safety bracketing will be implemented to guide next-step structure optimization and mechanism studies. Together, these results nominate acetylated glucopyranoside amidrazones as promising starting points rather than definitive chemical controls.