| Abstract [eng] |
Chitosan ((1→4)-2-amino-2-deoxy-d-glucose) is a natural polymer with promising applications in the food industry, cosmetics, and medicine. Its advantages include antimicrobial, antioxidative, and film-forming properties, as well as biocompatibility and biodegradability. Various modification strategies are currently being actively explored. Modifications such as alkylation or Schiff base formation allow improved applicability, enhanced antioxidant activity, and tailored physicochemical properties. This study focused on the analysis of specific chitosan modifications (acid hydrolysis, quaternization, and counterion exchange). Sephadex G-15 gel filtration, commonly used for desalting hydrolysates, was successfully applied for the controlled separation of low molecular weight COS fractions. Spectroscopic data showed that acid hydrolysis products, chito-oligosaccharides (COS), formed Schiff bases, unsaturated structures, and the vicinal diol system after the neutral hydrolysate concentration process. These compounds demonstrated exclusive antioxidant and reducing power activity of more than 100 %. Quaternization of COS and chitosan was performed using glycidyl trimethylammonium chloride, attaching a 2-hydroxypropyl trimethylammonium group on each glucosamine unit. Substitution degrees were approximately 1 for quaternized chitosan and 3 for quaternized COS. The introduction of the quaternary ammonium group was confirmed by ¹H NMR, ¹³C NMR, and FTIR analyses. Quaternized compounds with COS were further subjected to counterion exchange to gallate or ascorbate. The formation of their electrostatic complex was confirmed not only with 1H NMR and FTIR but also with UV-Vis spectroscopy. Among quaternized chitosan, gallate, and ascorbate complexes, the best antioxidant activity was of ascorbates and gallates. The best protective layer properties were prescribed to chito-oligosaccharides forming Schiff bases. A 2% solution of these compounds was a significantly better alternative to the ascorbate solution. |
