Synthesis, characterization and antimicrobial evaluation of two aromatic chitosan Schiff base derivatives

•4-Chloro benzaldehyde was coupled with chitosan to prepare Schiff base I.•Benzophenone was coupled with chitosan to prepare Schiff base II.•The chemical structures of the Schiff bases verified through FT-IR, TGA and DSC.•The antimicrobial activities of the Schiff bases increased more than chitosan.•The new Schiff bases could be applied as antimicrobial wound dresser.

Recently, there have been significant scientific interests to scientists for the chemical modifications of chitosan to increase its applications. The main objective of this study was to prepare two aromatic chitosan Schiff bases (I and II) via coupling with 4-chloro benzaldehyde and benzophenone respectively for improvement the antimicrobial property of chitosan. The chemical structures of the prepared Schiff bases verified through FT-IR, TGA and DSC. However, degrees of substitution were estimated using potentiometric analysis, and they were 7.9% and 4.17% for Schiff bases (I and II) respectively. Antimicrobial activities evaluation were conducted against three Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa and Salmonella sp.), two Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) and Candida albicans strain. The antimicrobial activities of the new derivatives increased significantly more than chitosan in most microorganisms. The minimum inhibitory concentration (MIC) of Schiff base (I) with concentration (50 μg/ml) exhibited the highest activity against C. Albicans with growth inhibition up to 27.42%. While, 50 μg/ml of Schiff base (II) showed high activity against E. coli, Salmonella sp., S. aeureus and B. cereus more than chitosan. The results clearly suggested that the new Schiff bases could be applied as antimicrobial wound dressing agents to ameliorate wound healing.

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