Synthesis and evaluation of the nematicidal and antifungal efficacy of carboxymethyl chitosan-based furan phenylhydrazone conjugates.

Plant-parasitic nematodes and soil-borne pathogenic fungi pose serious threats to global food security and agricultural sustainable development, representing a severe challenge to global agriculture. To overcome the limitations of traditional single-target control strategies and existing bio-based materials, this study designed and synthesized novel furan phenylhydrazone-functionalized carboxymethyl chitosan derivatives CMCS-Z1 to CMCS-Z4 via Schiff base reaction. Their structures were confirmed by 1H NMR and FT-IR spectroscopy. The degree of substitution, thermal stability, solubility, and cytotoxicity of the carboxymethyl chitosan derivatives were evaluated. Thermogravimetric analysis (TGA/DTG) indicated that chemical modification altered the thermal stability of the materials. The biological activities of the derivatives were systematically assessed. In vitro experiments demonstrated that CMCS-Z4, at a concentration of 1500 μg/mL, achieved inhibition rates of 92% and 94% against root-knot nematodes at 24 h and 48 h, respectively, which were comparable to the commercial nematicide fosthiazate. Validation by the greenhouse test-tube method showed that CMCS-Z4 at 1500 μg/mL resulted in an 81% inhibition rate of root galls on cucumber seedlings, without exhibiting significant phytotoxicity. In contrast, the other derivatives showed varying activities and generally lower root gall inhibition rates. Furthermore, CMCS-Z4 exhibited broad-spectrum antifungal activity against four plant pathogenic fungi (R.solain, F.rhododendron, F.oxysporum, A.alternate). This study confirms that grafting the furan phenylhydrazone pharmacophore onto the carboxymethyl chitosan backbone can successfully construct a novel agent with enhanced activity and dual functionality of nematicidal and antifungal properties, providing a potential candidate material for the integrated management of soil-borne disease complexes.