The bioactivity of chitosan oligosaccharides is closely related to its degree of polymerization. The bioactivity of chitosan oligosaccharides with specific degree of polymerization has attracted extensive attention. The results show that the structure-activity relationship between the degree of chitosaccharide polymerization and its activity is different according to the biological activity.
It has been reported that Chitohexaose Hexahydrochloride can effectively inhibit the metastasis of tumor 180 and solid tumor in mice. In addition, it can also effectively inhibit the growth of meth-A solid tumor in BALB/ C mice, indicating that Chitohexaose Hexahydrochloride is the basic functional factor of chitosan oligosaccharide's anti-tumor activity. Compared with other monosaccharides (Chitobiose Dihydrochloride, Chitotriose Trihydrochloride, Chitotetraose Tetrahydrochloride, and Chitopentaose Pentahydrochloride), Chitohexaose Hexahydrochloride showed a more obvious inhibitory effect on the proliferation and migration of TUMorinduced ECV304 cells. For antiangiogenic activity, the degree of polymerization had less effect, and dp8-12 chitosan oligosaccharide had better effect.
For the antimicrobial activity of chitooligosaccharides, the antimicrobial activity of chitooligosaccharides against Staphylococcus aureus increases with the increase of the degree of polymerization, and the degree of polymerization greater than 5 is the necessary condition for chitooligosaccharides to exert the antimicrobial activity. In addition, chitosan oligosaccharides with polymerization degree of 5-9 can induce the activity of phenylalanine aminolyase (PAL) and the production of H202 in arabidopsis thaliana suspension cells compared with DP3-6.
For antioxidant activity, chitosan oligosaccharides with low degree of polymerization had better hydroxyl radical scavenging activity than chitosan oligosaccharides with high degree of polymerization. Chitobiose Dihydrochloride and Chitotriose Trihydrochloride had stronger hydroxyl radical scavenging ability. Therefore, chitosan oligosaccharides with degree of polymerization greater than 2 were the effective components for hydroxyl radical scavenging. In terms of scavenging activity of superoxide radicals, chitosan oligosaccharides with molecular weight between 1000-3000 had better scavenging activity of superoxide radicals, while chitosan oligosaccharides with polymerization degree of 10-12 had better scavenging activity.
In terms of growing-promoting activity, the results of single polymerization degree on wheat seedlings showed that chitosan oligosaccharides could significantly promote the increase of root length, dry weight and fresh weight, and improve photosynthetic rate and chlorophyll fluorescence parameters. Based on the effects of chitosan oligosaccharides with different polymerization degrees on the growth and photosynthetic parameters of wheat seedlings, it was found that the degree of polymerization greater than 3 was the necessary condition for its growing-promoting activity. Compared with other chitosan oligosaccharide fragments with polymerization degree, Chitopentaose Pentahydrochloride, Chitohexaose Hexahydrochloride, Chitoheptaose Heptahydrochloride, Chitooctaose Octahydrochloride and DP8-10 had better activity. In general, Chitoheptaose Heptahydrochloride had the best activity. It can be seen that the degree of polymerization of chitooligosaccharides is closely related to its growth-promoting activity. Chitosan oligosaccharides with different degrees of polymerization have different effects on the growth parameters and photosynthesis-related parameters of wheat seedlings. Therefore, the purity of chitooligosaccharide monomers will affect its growth promoting activity. The size of the growth activity further reflects the importance of chitosan with a single degree of polymerization for the study of the growth-promoting mechanism of chitosan and its metabolic regulation mechanism on plants.