Novel Inulin Derivatives Modified with Schiff Bases: Synthesis, Characterization, and Antifungal Activity

In this paper, we report chemical modifications of inulin by seven kinds of aromatic Schiff bases, which are different from their substituent groups. The obtained inulin derivatives were confirmed by FTIR, H-1 NMR, and C-13 NMR. Then, we studied their antifungal activity against four kinds of plant pathogens involving Botrytis cinerea, Fusarium oxysporum f. sp. cucumerium Owen, Fusarium oxysporum f. sp. niveum, and Phomopsis asparagi by the mycelium growth rate method. The results revealed that all inulin derivatives were endowed with significant antifungal activity compared to inulin. Among them, 6-amino-(N-4-chlorobenzylidene)-6-deoxy-3,4-di-O-acetyl inulin (4CBSAIL) and 6-amino-(N-3,4-dichlorobenzylidene)-6-deoxy-3,4-di-O-acetyl inulin (3,4DCBSAIL), which were synthesized from p-chlorobenzaldehyde and 3,4-dichlorobenzaldehyde, could completely inhibit the growth of the test fungi at 1.0 mg/mL. The inhibitory indices of the inulin derivatives were related to the type, position, and number of substituent groups (halogens) on the Schiff bases. The results confirmed that it was feasible to chemically modify inulin with Schiff bases to confer high antifungal activity to inulin. The products described in this paper have great potential as alternatives to some harmful pesticides used for plant disease control