Extraction,Characterization And Biological Activity Of Sulfated Polysaccharides From Seaweed Dictyopteris Divaricata

The brown marine algal genus Dictyopteris divaricata belongs to the Dictyotaceae,a family which has proven to be a particularly rich and diverse source of natural products.To our knowledge,there are few studies done on polysaccharides of Dictyopteris divaricata,let alone their bioactivity.Therefore,in this study,the optimum extraction and biological activity of sulfated polysaccharides from Dictyopteris divaricata(DDSP)were investigated.Response surface methodology(RSM),based on a three-level,three-variable Box-Behnken design(BBD),was employed to obtain the best possible combinations for maximum polysaccharides yield.Subsequently,the characterization and biological activity of DDSP in vitro had been investigated to assess the potential applications as functional components.The main results are as follows:(1)Extraction and optimization of polysaccharides from Dictyopteris divaricataThe crude polysaccharides were extracted by water extraction and alcohol precipitation.The content of polysaccharides was determined by phenol sulfuric acid method.The extraction conditions(solid-liquid ratio,extraction time,extraction temperature)were optimized by response surface methodology.The optimum extraction conditions were as follows: liquid-solid ratio of 110mL/g,extraction time of 6h and extraction temperature of 100℃.Under these conditions,the experimental yield was 3.05%,which was in close agreement with the predicted value of 3.15% by the model.(2)Characterization of polysaccharides from Dictyopteris divaricataThe structures of polysaccharides were identified by modern chromatography and spectroscopic techniques such as IR,gas chromatography,Sephadex column chromatography,combining classical chemical methods such as acid hydrolysis,periodate oxidation and Smith degradation.The infrared spectrum indicated that DDSP contain stretching vibration of O-H bond,C-H bond,C=O stretching,sulfate group and pyranose ring.The average molecular weight of DDSP was 58.05 KDa.Gas chromatograph(GC)results showed that DDSP was composed of fucose,xylose,mannose,glucose and galactose with the corresponding molar ratio of4.45:2.74:1.00:2.94:1.35,followed by D-glucuronic acid(33.7%)and sulfate group(6%).Then DDSP was further analyzed by Smith degradation.The results of GC indicated that 1,3-linkages existed in the backbone of DDSP and some of fucose residues must be linked with 1,3-and 1,6-linkages.(3)Biological Activity of polysaccharides from Dictyopteris divaricataThe antioxidant activity of polysaccharides was detected by DPPH and hydroxyl radicals.The effects of polysaccharides on the proliferation and NO secretion of RAW264.7 macrophages in mice were detected by CCK-8 method and Griess reagent.The whitening and protection ability of DDSP was tested by detecting scavenging activity of superoxide radicals and tyrosinase inhibitory activity.The DPPH radical scavenging activity of DDSP was slightly increased in certain concentrations(0.1-0.5mg/mL),and the highest activity was 67% at 0.5mg/mL.The hydroxyl radical scavenging activity of DDSP exhibited concentration dependence at higher concentration(1-5mg/mL),which was 20.2% at the concentration of 5mg/mL.Biological activity showed that DDSP is competitive inhibition to tyrosinase and possessed the potential on stimulating immune response of RAW264.7 cells.In conclusion,DDSP is an ideal natural biological macromolecule.It has the potential to become a functional food additive and a raw material for green cosmetics,which provides a new idea for the comprehensive utilization of Dictyopteris divaricata.