title: Hydrophobic effect of amphiphilic derivatives of chitosan on the antifungal activity against Aspergillus flavus and Aspergillus parasiticus.
abstract: Low molecular weight amphiphilic derivatives of chitosan were synthesized, characterized and their antifungal activities against Aspergillus flavus and Aspergillus parasiticus were tested. The derivatives were synthesized using as starting material a deacetylated chitosan sample in a two step process: the reaction with propyltrimethyl-ammonium bromide (Pr), followed by reductive amination with dodecyl aldehyde. Aiming to evaluate the effect of the hydrophobic modification of the derivatives on the antifungal activity against the pathogens, the degree of substitution (DS₁) by Pr groups was kept constant and the proportion of dodecyl (Dod) groups was varied from 7 to 29% (DS₂). The derivatives were characterized by ¹H-NMR and FTIR and their antifungal activities against the pathogens were tested by the radial growth of the colony and minimum inhibitory concentration (MIC) methods. The derivatives substituted with only Pr groups exhibited modest inhibition against A. flavus and A. parasiticus, like that obtained with deacetylated chitosan. Results revealed that the amphiphilic derivatives grafted with Dod groups exhibited increasing inhibition indexes, depending on polymer concentration and hydrophobic content. At 0.6 g/L, all amphiphilic derivatives having from 7.0 to 29% of Dod groups completely inhibited fungal growth and the MIC values were found to decrease from 4.0 g/L for deacetylated chitosan to 0.25-0.50 g/L for the derivatives. These new derivatives open up the possibility of new applications and avenues to develop effective biofungicides based on chitosan.
authors.affiliation: Department of Chemistry and Environmental Sciences, Institute of Biosciences, Humanities and Exact Sciences-IBILCE, São Paulo State University-UNESP, São José do Rio Preto, São Paulo 15054-000, Brazil.
authors.forename: Ricchard Hallan Felix
authors.initials: RH
authors.lastname: Viegas de Souza
authors.forename: Mirelli
authors.initials: M
authors.lastname: Takaki
authors.forename: Rafael
authors.initials: R
authors.lastname: de Oliveira Pedro
authors.forename: Juliana
authors.initials: J
authors.lastname: dos Santos Gabriel
authors.forename: Marcio José
authors.initials: MJ
authors.lastname: Tiera
authors.forename: Vera Ap
authors.initials: VA
authors.lastname: de Oliveira Tiera
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D001230:Aspergillus / Q000187:drug effects*; D001231:Aspergillus flavus / Q000187:drug effects*; D048271:Chitosan / Q000737:chemistry / Q000494:pharmacology*; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000935:Antifungal Agents; D000644:Quaternary Ammonium Compounds; C008864:3-phenylpropyltrimethylammonium; D048271:Chitosan