Antimicrobial activity of novel modified aminated chitosan with aromatic esters

Abstract

Novel modified aminated chitosan with aromatic esters has been synthesized and characterized, and finally, their antimicrobial activities were evaluated. p-hydroxymethyl benzoate, 2,4-dihydroxymethyl benzoate, and methyl salicylate were reacted with aminated chitosan via the original and the introduced amino groups. The chemical structure of the obtained amides was verified through elemental analysis, IR spectroscopy, 1HNMR spectra, and TGA. The gram-negative bacterium (Escherichia coli (NCIM 2065), Salmonela typhi, and Pseudomonas aeruginosa) and the gram-positive bacterium (Staphylococcus aureus) following microorganisms were chosen to test the antimicrobial activity of the synthesized polymers. Moreover, the fungi (C. albicans (SC5314), Cryptococcus neoformans, Aspergillus flavus and Aspergillus niger) were used. The antimicrobial activity of aminated chitosan on fungi, gram-positive bacteria, and gram-negative bacteria show small inhibitory effect against fungi species; an increase in the inhibition of gram-negative more than gram-positive bacteria is observed. The antimicrobial activity of aminated chitosan modified with p-hydroxymethyl benzoate (XII) and 2,4-dihydroxymethyl benzoate (XIII) shows a higher inhibitory effect. The inhibitory actions are observed against a wide variety of microorganisms, including fungi, gram-positive bacteria, and gram-negative bacteria. Diameter of inhibition zones was ranged between 7 and 16 mm, 14 mm and 11–26 mm on gram-negative bacteria, gram-positive bacteria and on fungi, respectively. However, aminated chitosan modified with methyl salicylate (XIV) shows a little effect against the test microorganisms. Generally, the potency of inhibition varied according to the substitutions.