Synthesis, Characterization, and Anti-Phytopathogen Evaluation of 6-Oxychitosan Derivatives Containing N-Quaternized Moieties in Its Backbone

The structure modification of chitosan has great application potential. 6-Oxychitosan was prepared by specially oxidizing the C6-OH of chitosan, then 6-oxychitosan was reacted with three kinds of aldehydes to prepare N-quaternized 6-oxychitosan derivatives in this paper. The derivatives were characterized by FT-IR, NMR, and elemental analysis. The antimicrobial activity of these derivatives was tested against two common plant-threatening fungi and three plant disease bacteria. The results showed that N-quaternized 6-oxychitosan derivatives had good water-solubility and excellent antimicrobial activity. Moreover, derivative 3 which connected 8-hydroxyquinolines had the highest antimicrobial activity than the other derivatives. The inhibitory indices of derivative 3 against V. albo-atrum and P. hibernalis are 89.1% and 72.8% at 0.4 mg/ml. The MICs of 3 against X. oryzae, P. syringae, and E. rhapontici were 625, 625, and 156 mg/l, respectively. All the results indicate that derivative 3 has the potential of becoming an alternative to harmful agricultural chemicals.