New Polycationic Arabinogalactan Derivatives with the CHPTAC System: Structure, Properties and Antioxidant Activity

Cationic arabinogalactan (AG) derivatives with a degree of substitution (0.02–0.19) containing quaternary ammonium groups were prepared by reaction of the etherification of (3-Chloro-2-hydroxypropyl)-trimethylammonium chloride (CHPTAC), catalyzed by an aqueous solution of sodium hydroxide. The effect of etherification was assessed by the degree of substitution (DS). The DS values of the AG samples were controlled by the varied pH of the reaction mixture from 10 to 12 and the duration of the process quaternization (2, 18, 24, 30 and 72 h). In comparison, the quaternized samples of the AG were characterized by physicochemical research methods, such as elemental analysis, gel permeation chromatography (GPC), Fourier Transform Infrared (FTIR), and 1H nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA). Furthermore, the improved antioxidant capacity of the quaternized AGs was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. It was found that the most favorable conditions for the quaternization process were pH = 12, duration and temperature of the process of 31.6 h and 50 °C, respectively. The esterification reaction was accompanied by hydrolysis side reactions at a longer process.