Monomer composition of chitooligosaccharides obtained by different degradation methods and their effects on immunomodulatory activities.

Three kinds of chitooligosaccharides were prepared using traditional (ZCOS), microwave irradiation (WCOS), and enzymatic hydrolysis (YCOS), and their monomer compositions and in vitro and in vivo immunomodulatory activities were determined. ZCOS was mainly comprised of disaccharides and trisaccharides; WCOS was mainly comprised of disaccharides to hexasaccharides with or without acetyl groups; and YCOS was mainly comprised of trisaccharides to pentasaccharides without acetyl groups. Differences in monomer composition and acetyl groups affected their immunomodulatory activities. Chitooligosaccharides degraded by different methods: all significantly stimulated the immune system by acting through cellular and humoral immunities. WCOS, obtained by microwave irradiation, had the best immunomodulatory activity. It significantly increased the spleen index and significantly stimulated delayed-type hypersensitivity compared the other two chitooligosaccharides. These activities might have been the result of the hexamer and acetyl groups of WCOS.