Molecular Modification of Polysaccharides and Resulting Bioactivities

Abstract

Polysaccharides are ideal natural resources for supplements and pharmaceuticals that have received more and more attention over the years. Natural polysaccharides have been shown to have fewer side effects, but because of their inherently physicochemical properties, their bioactivities were difficult to compare with those of synthetic drugs. Thus, researchers have modified the structures and properties of natural polysaccharides based on structure-activity relationships and have obtained better functionally improved polysaccharides. This review focuses on the major modification methods of polysaccharides, and discusses the effect of molecular modification on their physicochemical properties and bioactivities. Molecular modification methods mainly include chemical, physical, and biological changes. Chemical modification is the most widely used method; it can significantly increase the water solubility and bioactivities of polysaccharides by grafting onto other groups. Physical and biological modifications only change the molecular weight of a polysaccharide, and thereby change its physicochemical properties and bioactivities. Most of the molecular modifications bring about an increase in the antioxidant activity of polysaccharides, and among these, sulfated and acetylated modifications are very common. Furthermore, phosphorylation modification is the most common application to increase antitumor activity, and modified polysaccharides have been shown to have anti-HIV activity as the result of sulfated modification.

Dual‐frequency ultrasound‐assisted alcohol/salt aqueous two‐phase extraction and purification of Astragalus polysaccharides

“…A comparison of the current study findings with the aforementioned showed that APS extracted under dual‐frequency ultrasound had a greater potential to lower the proliferation of ˙OH radicals, and could greatly reduce oxidative impairments. This result is supported by Li et al () who have reported that ultrasonic disruption intensifies the degradation of high molecular weight polysaccharides to low molecular weight polysaccharides since low molecular weight polysaccharides possess a more reductive hydroxyl group to accept and eradicate free radicals (Leung, Zhao, Ho, & Wu, ). IC 50 value were reported as 0.42, 0.38, 0.43, and 0.56 mg/ml for APS 10 , APS 20 , APS 30 , and APS control , respectively.…”

Temperature‐responsive alginate‐g‐poly(N,N‐diethylacrylamide) copolymer: Synthesis, characterization, and swelling behavior

“…As shown in the figure, elution volume of graft copolymers shifted to higher values compared to that of alginate, which resulted in a significant decrease in the molecular weights as presented in Table . This result demonstrates that microwave irradiation used in the grafting reaction may cause cleavage of some bonds in the alginate chains . However, when grafting percentages increased from 58% to 88%, all types of average molecular weights increased proportionally, due to the formation of much longer PDEAAm chains in the copolymer structure.…”

Effect of ultrasonic degradation of hyaluronic acid extracted from rooster comb on antioxidant and antiglycation activities

“…Ultrasonic degradation of polysaccharides was shown to enhance hydroxyl and superoxide anion radical scavenging capacity, chelating iron ion ability and reducing power (Zhou et al 2008); this phenomenon could be attributed to the fact that a decreasing of Mw and viscosity of HA may influence its bioactivities. In addition, the long main chain and high viscosity of polysaccharides decrease the absorption and diffusion properties, thus limiting their biological activity (Li et al 2016). Therefore, an effective method to resolve this problem is by degrading the main chain (Zhou et al 2008).…”