Synthesis, characterization and biological activity of C₆-Schiff bases derivatives of chitosan

C₆-Schiff bases derivatives of chitosan were synthesized for the first time. C₂-amino groups and C₃-hydroxy groups were firstly protected by CuSO₄·5H₂O, and the C₆-hydroxy was then transformed into aldehyde, which then reacted with anilines through nucleophilic addition to introduce the CN group at C₆-position in chitosan chain. Finally, C₆-Schiff bases derivatives of chitosan were got by the deprotection of C₂-NH₂ with cation exchange resin. The structures and properties of the new synthesized products were characterized by Fourier transform infrared spectroscopy, ¹³C NMR, SEM image, and elemental analysis. The antibacterial activities of derivatives were tested in the experiment, and the results showed that the prepared chitosan derivatives had significantly improved antibacterial activity toward Staphylococcus aureus and Escherichia coli. The Cytotoxicity test showed that the prepared chitosan derivatives had low Cytotoxicity, compared with chitosan and C₂-benzaldehyde Schiff bases of chitosan. This paper allowed a new method for the synthesis of Schiff bases of chitosan, which was enlightening.