Chemical Modification of Chitosan with Bioactive Molecules: A Sustainable Approach for Advanced Film Development

This study presents the synthesis of a new chitosan (CS) derivative incorporating eugenol (EU), a natural compound known for its strong antioxidant properties, with the aim of comparing its properties to those of the previously described thiazolium-chitosan derivative (CS-MTBAQ), employed as antimicrobial component. The functionalization was achieved through a thiol-ene reaction, enabling the covalent bonding of EU and thiol modified chitosan (CS-SH). After detailed characterization of the resulting derivative (CS-SH-EU), a comparative analysis of its antioxidant activities was conducted, revealing that CS-SH-EU films exhibited 25% higher antioxidant efficiency compared to those with CS modified with MTBAQ. Both derivatives were incorporated into chitosan-based films at 10 wt%, which were further reinforced with chitin nanowhiskers at two concentrations, 1 and 5 wt%. The antioxidant, mechanical and structural properties of these films were extensively evaluated as well as the yellowness index and water vapor transmission. The inclusion of these derivatives containing eugenol and thiazolium groups and the chitin nanowhiskers enhanced the mechanical performance, water barrier properties, and antioxidant activity maintained the visual appearance. The formulation applied as coating on strawberries was able to extend their self-life by creating an effective barrier. The findings evidence that the obtained films present a promising alternative for developing active packaging materials, combining enhanced antioxidant efficiency with excellent mechanical and biodegradable properties.