Enzyme-assisted extraction of a cup plant (Silphium perfoliatum L.) Polysaccharide and its antioxidant and hypoglycemic activities

Pharmacotherapy using natural substances can be currently regarded as a very promising future alternative to conventional therapy. As biological macromolecules, polysaccharide together with protein and polynucleotide, are extremely important biomacromoleules which play important roles in the growth and development of living organism. Polysaccharide is important component of higher plants, membrane of the animal cell and the cell wall of microbes. It is also closely related to the physiological functions. Recently, increasing attention has been paid on polysaccharides as an important class of bioactive natural products. Numerous researches have demonstrated the bioactivities of natural polysaccharides, which lead to the application of polysaccharides in the treatment of disease. In this paper, the various aspects of the investigation results of the bioactivities of polysaccharides were summarized, including its diversity pharmacological applications, such as immunoregulatory, anti-tumor, anti-virus, antioxidation, and hypoglycemic activity, and their application of polysaccharides in the treatment of disease are also discussed. We hope this review can offer some theoretical basis and inspiration for the mechanism study of the bioactivity of polysaccharides.

The impacts of three extraction techniques, including hot water extraction (HWE), pressurized water extraction (PWE), and microwave assisted extraction (MAE), on the physicochemical characteristics, antioxidant activities, in vitro binding properties, and in vitro inhibitory activities on α-amylase and α-glucosidase of okra polysaccharides (OPPs) were investigated and compared. The extraction yields, constituent monosaccharides, and FT-IR spectra of OPP-W, OPP-P, and OPP-M extracted by HWE, PWE, and MAE, respectively, were similar. However, their molecular weights, intrinsic viscosities, uronic acids, and degree of esterification were different. Furthermore, results showed that OPP-W, OPP-P, and OPP-M exhibited remarkable antioxidant activities, binding capacities, and inhibitory activities on α-amylase and α-glucosidase. Indeed, the antioxidant activities of OPP-W were significantly lower than those of OPP-M and OPP-P, which might be attributed to the low molecular weights and high contents of unmethylated galacturonic acid of OPP-P and OPP-M. However, the binding capacities and inhibitory activities on α-amylase and α-glucosidase of OPP-W and OPP-P were similar, but significantly higher than those of OPP-M, which might be attributed to the low molecular weights of OPP-M. Results suggested that the PWE method could be a good potential technique for the extraction of OPPs with high bioactivities for industrial applications.

A new, simple, and effective method to graft gallic acid (GA) onto chitosan (CS) in aqueous solution in the presence of carbodiimide and hydroxybenzotriazole was developed. The grafting amount of GA reached as much as 209.9 mg/g of copolymer, which appears as the highest one among the reported literature, and the grafting degree of GA to CS was adjustable with modulation of the mass ratio of GA to CS. The covalent insertion of GA onto the polymeric backbones was confirmed by UV-vis and (1)H NMR analyses. Grafting endowed the resulting copolymer GA-grafted-CS (GA-g-CS) with both the advantages of CS and GA. The antioxidant capacity of GA-g-CS was much higher than that of the plain CS examined by assays of DPPH, superoxide, and ABTS radicals scavenging activities, reducing power, chelating power, inhibition of lipid peroxidation, ferric reducing antioxidant potential, and β-carotene-linoleic acid assays. Particularly, GA-g-CS showed significantly higher antioxidant activity than GA in β-carotene-linoleic acid assay. Furthermore, the viscosity of GA-g-CS was significantly higher than that of CS. The present study developed a novel approach to synthesize GA-g-CS that could be a potential biomaterial in food industries.