Hydrophobic and Electrostatic Effects of Chitosan Derivatives on the Antifungal Activity against Aspergillus flavus

In this work, chitosan derivatives containing anionic and hydrophobic groups were obtained by means of grafting with α-ketoglutaric acid (Ket) and dodecyl groups. The derivatives were characterized by 1H-NMR and FTIR techniques and their associative behavior in aqueous solution was studied by fluorescence spectroscopy. The insertion of both groups strengths hydrophobic interactions and DLS measurements showed that selfassociation leads to the formation of micrometric aggregates whose superficial charge depends on pH. Mycelial growth inhibition assays against A. flavus fungus were performed in the presence of increasing concentrations of the different polymers1. All the derivatives showed higher inhibitory effects than deacetylated chitosan (CH). The insertion of anionic groups reinforced the hydrophobic interactions and the ketoglutaric derivatives (DS = 15 and 25%) inhibited the growth of the fungus in 80% in the concentration of 2.0 g / L. The insertion of dodecyl groups and ketoglutaric acid provided zwitterionic derivatives that exhibited higher antifungal activities, which was attributed to hydrophobic interactions between the amphiphilics and the hydrophobic constituents of the cell wall.