Biologically active polymers: Modification and anti-microbial activity of chitosan derivatives

The principal derivative of chitin is chitosan, which is obtained by deacetylation of chitin. Chemical modification of synthetic and natural polymers is a convenient way to obtain materials with unique chemical and physical properties. Chitosan has an amino group at C-2 which is important because amino groups are nucleophilic and readily react with electrophilic reagents. Chitosan modified under mild conditions often results in regioselectivity for the C-2 amino group. In the present work, this reactivity was exploited to attach biologically active moieties into the amino groups of chitosan to yield anti-microbial chitosans. Specifically, vanillin, p-hydroxybenzaldehyde, p-chlorobenzaldehyde, anisaldehyde, methyl 4-hydroxybenzoate, methyl 2,4-dihydroxybenzoate, propyl 3,4,5-trihydroxybenzoate and 2-hydroxymethylbenzoate were attached. The anti-microbial activity of these modified chitosans was explored against fungi such as Candida albicans SC5314, Aspergillus flavus and Fusarium oxysporium. Also, they were tested against bacteria such as Bacillus subtilis, Escherichia coli and Staphylococcus aureus. These modified chitosans were found to be highly active toward fungi species more than bacterial species.