Síntese e Caracterização de Derivados de Quitosana Hidrofóbizados com Óleo Essencial de Citronela (Cymbopogon winterianus)

Abstract

Hydrophobic chitosan (CS) derivatives were prepared by means of Schiff-based N-Alkylation reactions using as the source of alkyl groups the 3,7-dimethyl-oct-6-enal unsaturated aldehyde, the major component of citronella essential oil (Cymbopogon winterianus), followed by reduction with sodium borohydride. The reaction was carried out in aqueous medium under homogeneous conditions and at room temperature. The synthesized derivatives received the CS-CTN code and were characterized by Elementary Analysis, Unsaturation Test, Solubility Test, FTIR Spectroscopy, Proton and Carbon 13 Nuclear Magnetic Resonance, Degree of Substitution, Mean Particle Size, PDI, Zeta Potential, Thermogravimetry and Differential Scanning Calorimetry. The hydrophobization of chitosan was evidenced by FTIR, in which new bands appear in 2929 cm-1 due to the presence of the methyl group together with the presence of strong band in 1580 cm-1 related to N-substitution. In addition, proton and carbon NMR show, in addition to the chemical shifts characteristic of chitosan, signals related to methyl groups, which corroborate the insertion of the alkyl chain in the polymer backbone. The DS of the derivatives show that for more dilute chitosan solutions, the greater the amount of alkyl groups inserted in the polymer chain. These data were confirmed by elemental analysis and by 1H NMR. The unsaturation test was positive for the new compounds, proving the presence of unsaturation in the samples, which probably indicates that the inserted chain has a double bond. The particle size distribution was mostly unimodal, with particle sizes in the range of 218-274 nm and zeta potential ranging from +0.44 to +0.63 mV. The low values for the PDI indicate regularity in the sizes of the polymer chains. Thermal analyzes have shown that the derivatives are less stable than the original chitosan molecule. The products obtained are likely candidates for use in the encapsulation and transport of active principles of interest in the food area, pharmacy and medicine.