Antimicrobial Activity of Amino-Derivatized Cationic Polysaccharides.

To improve the antimicrobial property of chitosan, water-soluble chitosan modified in their quaternary ammonium groups were synthesized. The antimicrobial properties were evaluated against , , and The activities increased with increasing cationic charges and the length of the alkyl chain as follows amino-chitosan, dimethylaminoethyl-chitosan, dimethylpropyl amino-chitosan, dimethylamino-1-propyl-chitosan, diethylaminoethyl (DEAE)-chitosan, and quaternized DEAE-chitosan. The modified cationic chitosans showed high antimicrobial property against -Gram-positive bacteria, but were less active towards yeast ( and and -Gram-negative bacteria. The simple structure of the Gram-positive bacteria may explain why the cationic chitosan derivatives are more active towards than yeast and . The target sites of the chitosan derivatives are assumed to be the cytoplasmic membranes of microorganisms. The antimicrobial activities were strongly dependent on the cationic charge and the molecular weight. It can be suggested that these cationic chitosan derivatives have potential as antimicrobial agents.