Anti-lipid oxidation of chitosan oligosaccharide modified by laccase/TEMPO reaction

Carboxylated chitosan oligosaccharide (C–COS) was prepared by selective oxidation of chitosan oligosaccharide (COS) using laccase/2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) system to change its hydroxyl group on C6 to carboxyl group. Free radical-induced in vitro lipid oxidation experiments were performed using linoleic acid as the experimental subject. Inhibitory effects of COS and C–COS on lipid peroxidation were assessed by comparing the generation of a conjugated diene, MDA, and superoxide. Combining FTIR, 1H NMR, and GC-MS for structural analysis. Results show that C–COS and COS treatment suppressed lipid oxidation, and C–COS has better inhibition effects than COS. The primary inhibition mechanism lies in the carboxylic acid root of C–COS on C6 chelates with metal ions, reducing the generation of free radicals. Meanwhile, it exposes more C2 amino sites outside the sugar chain, promoting the capture of free radicals. This two-way action plays a synergistic role, effectively inhibiting free radicals from attacking fatty acids, avoiding lipid peroxidation.