Preparation, characterization and antimicrobial evaluation of novel cinnamyl chitosan Schiff base.

Cinnamyl chitosan Schiff base was prepared by coupling chitosan with trans-Cinnamaldehyde -the mean component of cinnamon oil- under acidic conditions to form cinnamyl chitosan Schiff base. Parameters affecting coupling process such as chitosan/cinnamaldehyde molar ratio, reaction time and reaction temperature were studied to optimize reaction conditions. The progress of Schiff base formation was monitored by increasing of absorption of polymer solution at certain wave length 310 nm and decline in ion exchange capacity of chitosan derivatives from 5.78 to 4.16 meq/g. The changing in chitosan chemical structure was proved by FT-IR, electronic spectra, and Scan electron microscope. Moreover, thermal characterization using TGA and DSC analysis show that the prepared derivatives exhibit more thermal stability than chitosan itself. The results show decrease of samples water uptake and solubility in aqueous acidic solution by increased substitution degree as a result of increase in hydrophobicity character by modification. Antimicrobial activity of cinnamyl chitosan Schiff base against five different bacteria strains and three fungal species was investigated. Antibacterial activity was tested against five different bacterial strains (two gram positive: Staphylococcus aureus and Streptococcus pyogenes & three gram negative: Pseudomonas aeruginosa, Proteus vulgaris and Shigella). Also, antifungal activity was done against three different fungal species (Fusserium, Aspergillus Niger and Penicillium). The results showed increasing in antibacterial activity of substituted chitosan against both gram negative and gram positive bacteria by increase the degree of substitutions, also, it showed directly dose dependant. Antibacterial activity of chitosan Schiff base was declined at high pH as a result of decreasing the solubility especially for high substituted polymer. As the same, antifungal test shows increase of antifungal activity of Schiff bases rather than chitosan itself. Antifungal activity is dose dependant and increased by increased degree of substitution.