Synthesis and Characterization of Inulin Derivatives Bearing Urea Groups with Promising Antifungal Activity

The toxicity concerns associated with chemical fungicides currently on the market have resulted in an increased demand for alternative ecofriendly fungicides. As a biodegradable and biocompatible dietary fiber, inulin shows potential as such a compound, given its lack of toxicity. In the current study, seven novel inulin derivatives with promising antifungal activity (BUCAIL, 2CBUCAIL, 3CBUCAIL, 4CBUCAIL, 3,4CBUCAIL, 2FBUCAIL, and 2BBUCAIL) are synthesized via condensation reactions of chloroacetyl inulin (CAIL) with urea groups bearing 4-amino-pyridine. Their structures are confirmed using FT-IR, H-1 NMR, C-13 NMR, and elemental analysis. Their antifungal activity against three kinds of phytopathogen (Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, and Fusarium oxysporum f. sp. cucumebrium Owen) is evaluated using the mycelial growth rate in vitro at concentrations of 0.10, 0.25, 0.50, 0.75, and 1.0 mg mL(-1). Results reveal that all seven inulin derivatives show improved antifungal properties compared with unmodified inulin, and two obvious inhibition rules are found: 3,4CBUCAIL > 4CBUCAIL > 3CBUCAIL > 2CBUCAIL > BUCAIL > CAIL > inulin and 2FBUCAIL > 2CBUCAIL > 2BBUCAIL > BUCAIL > CAIL > inulin. Thus, the introduction of urea groups into inulin derivatives could be key to increasing the antifungal activity of such compounds.