Synthesis of urea-functionalized chitosan derivatives for potential antifungal and antioxidant applications.

• Five novel urea-functionalized chitosan derivatives were synthesized. • Chitosan derivatives bearing urea groups had better bioactivity than chitosan. • Urea groups had a positive effect on biological activity. • The electronegativity of urea groups could affect the biological rule of products. • Chitosan derivatives bearing urea groups showed relatively low cytotoxicity. In the current study, five novel urea-functionalized chitosan derivatives were synthesized via condensation reactions of chloroacetyl chitosan (CTCS) with urea groups bearing nitrogen-containing heterocycles. In order to identify the structure characteristics of chitosan derivatives, FT-IR, 1H NMR spectroscopy, and elemental analysis were carried out. The antifungal activity of the derivatives against four species of phytopathogen (Fusarium oxysporum f. sp. niveum , Phomopsis asparagus , Fusarium oxysporum f. sp. cucumebrium Owen, and Botrytis cinerea) was evaluated. Furthermore, the antioxidant activity of chitosan derivatives was tested by hydroxyl-radical scavenging and superoxide-radical scavenging assays. The results indicated that chitosan derivatives bearing urea groups displayed superior bioactivity compared with chitosan. Besides, L929 cells were adopted for cytotoxicity test of chitosan and synthesized samples by CCK-8 assay and all samples showed decreased cytotoxicity. These results suggested that the novel urea-functionalized chitosan derivatives could be an ideal biomaterial for antifungal and antioxidant applications. [ABSTRACT FROM AUTHOR]