Synthesis and Characterization of N-(maleoyl) chitosan at Different Degrees of Substitution with Antibacterial Activity

By : Mohamed E. I. Badawy, Entsar I. Rabea

Page No: 249-259

Abstract
A biopolymer chitosan is an attractive polysaccharide obtained by deacetylation of an abundant natural biopolymer chitin. To improve the potential of chitosan application in different fields, structural modification is needed especially in enhancing of its antimicrobial activity. In this study, chitosan in a solution of 2% aqueous acetic acid-methanol (1:1, v/v) was reacted with malic anhydride at 0.1, 0.3, 0.5, 0.8, and 1.0 mol/glucosamine unit resulting water-soluble of N-(maleoyl) chitosan products with degrees of substitution (DS) of 0.13, 0.25, 0.40, 0.49, and 0.58, respectively. These products were characterized by using 1 H-NMR spectroscopy. The compounds showed high solubility in a wide pH range than chitosan itself. The antibacterial activity was evaluated in vitro by broth micro-dilution technique as a minimum inhibitory concentration (MIC) against four plant pathogenic bacteria Erwinia carotovora, Ralstonia solanacearum, Rhodococcus fascians, and Rhizobium radiobacter. The results proved that the inhibitory property and water solubility of the synthesized chitosan derivatives, with increase of the DS, exhibited a remarkable improvement over chitosan. The product with a DS of 0.58 was the most active one with MIC of 550, 700, 275, and 400 mg/L against E. carotovora, R. solanacearum, R. fascians, and R. radiobacter, respectively. These compounds based on a biodegradable and biocompatible chitosan could be used as potentially antimicrobial agents in crop protection instead of hazardous synthetic pesticides.

Authors :
Mohamed E. I. Badawy : Department of Pesticide Chemistry and Technology, Faculty of Agriculture, 21545-El-Shatby, Alexandria University, Alexandria, Egypt
Entsar I. Rabea : Department of Plant Protection, Faculty of Agriculture, Damanhour University, 22516-Damanhour, Egypt