Synthesis, Characterization, and Antifungal Activities of Amphiphilic Derivatives of Diethylaminoethyl Chitosan against Aspergillus flavus.

Amphiphilic derivatives of diethylaminoethyl chitosan (DEAE-CH) were synthesized using a two-step process involving initial substitution with diethylaminoethyl (DEAE) groups followed by reductive amination with dodecylaldehyde. The synthesized derivatives were characterized by (1)H NMR, gel permeation, and FTIR. The associative behaviors of these compounds in aqueous solution were studied using fluorescence spectroscopy, whereas their antifungal activities against Aspergillus flavus were evaluated in terms of mycelial growth. The effects of deacetylated chitosans and their derivatives on the mycelial growth of A. flavus were evaluated at several polymer concentrations (0.05-1.0 g/L), and the results were compared. The inhibition indices of the deacetylated chitosans increased with increasing Mw (16.9 kDa < 176 kDa < 517.7 kDa); however, derivatives with a combination of either a high molecular weight (Mw) and low hydrophobicity or a low Mw and high hydrophobicity were the most effective in inhibiting the in vitro radial growth of A. flavus.