Evaluation of free radical‐induced structural changes and their effect on antioxidant and anti‐inflammatory activities of UV/H 2 O 2 ‐degraded dextrans

Although ultraviolet (UV)/H 2 O 2 treatment could effectively improve the bioactivities of polysaccharides, the relationship between free radical‐induced structural changes and the bioactivities of products remains unknown. Therefore, this work investigated the changes in the chemical characteristics and chain conformations of degraded dextrans by the UV/H 2 O 2 system as well as their antioxidant and anti‐inflammatory activities. The apparent degradation efficiencies of dextrans under different UV/H 2 O 2 parameters were first investigated. UV/H 2 O 2 treatment effectively destroyed the pyranose rings and glycosidic bonds of dextrans and significantly improved their uronic acid and carboxy contents. Furthermore, conformational studies revealed that besides the rapid decrease in the molecular weight, the compact spherical conformation of dextrans was gradually depolymerized into the flexible random coil conformation. Moreover, the significant antioxidant and anti‐inflammatory activities of the degraded dextrans were mainly attributed to their more extended random coil chains, increased quantity of reducing groups, and lower molecular sizes. This study contributes to investigating the structure–activity relationship of polysaccharides prepared by free radicals‐mediated degradation.