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.

Structure and antimicrobial activities of benzoyl phenyl-thiosemicarbazone-chitosans.

Previously, we had prepared acetyl phenyl-thiosemicarbazone derivatives of chitosan, and their antimicrobial activities were analyzed. The purpose of the present study was to further assess the relationship between the structure and antimicrobial activities of benzoyl phenyl-thiosemicarbazone-chitosan. Ten new benzoyl phenyl-thiosemicarbazone-chitosans were prepared and their structures were characterized by FT-IR and elemental analysis. The antimicrobial experiment against four species of bacteria and four crop-threatening pathogenic fungi were conducted based on the derivatives of chitosan with different molecular weight at different concentrations. The results indicated that the antimicrobial activities of benzoyl phenyl-thiosemicarbazone derivatives are much better than that of pure CS. The value of the minimum inhibition concentration (MIC) and the minimum bactericidal concentration (MBC) of the derivatives against Escherichia coli was 7.03 and 225 µg mL(-1) respectively. All of the derivatives had significant inhibiting effect on the investigated fungi in the concentration of 50-500 µg mL(-1), and the maximum inhibitory index was 94.74%. These results indicate that the derivatives have potential ability used as antibacterial reagent in agricultural field.

The influence of the different inductivity of acetyl phenyl-thiosemicarbazone-chitosan on antimicrobial activities.

Ten different acetyl phenyl-thiosemicarbazone derivatives of chitosan were synthesized. Their structures were characterized by FT-IR and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria and four crop-threatening pathogenic fungi were investigated in this paper. The results indicated that the antimicrobial activities of acetyl phenyl-thiosemicarbazone derivatives are much better than that of pure CS. The minimum value of MIC and MBC of the derivatives against Escherichia coli was 7.03 and 225 µg mL(-1), respectively. All of the derivatives had significant inhibiting effect on the investigated fungi in the concentration of 50-500 µg mL(-1), and the maximum inhibitory index was 93.10%. The bioactivities of the derivatives have relationship with the grafted groups with different inductivity.