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Hydrophobic Effect of Amphiphilic Derivatives of Chitosan on the Antifungal Activity against Aspergillus flavus and Aspergillus parasiticus
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
* Author to whom correspondence should be addressed.
Received: 19 February 2013; in revised form: 20 March 2013 / Accepted: 9 April 2013 / Published: 15 April 2013
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.
Keywords: chitosan; antifungal activity; derivatives; amphiphilic; Aspergillus flavus; Aspergillus parasiticus
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Viegas de Souza, R.H.F.; Takaki, M.; de Oliveira Pedro, R.; dos Santos Gabriel, J.; Tiera, M.J.; de Oliveira Tiera, V.A. Hydrophobic Effect of Amphiphilic Derivatives of Chitosan on the Antifungal Activity against Aspergillus flavus and Aspergillus parasiticus. Molecules 2013, 18, 4437-4450.
Viegas de Souza RHF, Takaki M, de Oliveira Pedro R, dos Santos Gabriel J, Tiera MJ, de Oliveira Tiera VA. Hydrophobic Effect of Amphiphilic Derivatives of Chitosan on the Antifungal Activity against Aspergillus flavus and Aspergillus parasiticus. Molecules. 2013; 18(4):4437-4450.
Viegas de Souza, Ricchard H.F.; Takaki, Mirelli; de Oliveira Pedro, Rafael; dos Santos Gabriel, Juliana; Tiera, Marcio J.; de Oliveira Tiera, Vera A. 2013. "Hydrophobic Effect of Amphiphilic Derivatives of Chitosan on the Antifungal Activity against Aspergillus flavus and Aspergillus parasiticus." Molecules 18, no. 4: 4437-4450.