Extraction, Purification And Characterization Of Ploysaccharides From Bangia Fusco-purpurea

Bangia fusco-purpurea is a kind of red alga which is an economic aquaculture alga in Fujian province. In this paper, the extraction process, purification method , the physical and chemical characters of Bangia fusco-purpurea polysaccharides (BP) were systematically studied, and its antioxidant activity in vitro were also been preliminarily explored.We compared different solvents effect on extraction yield and sulfate content of polysaccharides, the method of hot water, cold water, dilute acid and dilute alkali were used in the experiment. The result showed that hot water is the best solvent. According to single factor and orthogonal test, the optimum conditions of extract process were as follows: extracting temperature was 90℃, extracting time was 2 h, the ratio of alga to solvent was 1:30 and extracting times was 3. The maximum yield of polysaccharide was 5.97% under this optimized conditions; Ultrasonic method was used as an auxiliary method in the extraction of polysaccharide. According to single facter and orthogonal test, the optimum conditions of extractions were: extracting temperature was 80℃, extracting time was 80 minutes, the ratio of alga to solvent was 1:70 and the power of ultyasonic was 200 W. The maximum yield of polysaccharide was 9.69% under this condition; The ethanol concentration of 75% and the concentrate ratio of extracting solution of 1: 3 were optimized for polysaccharide precipitation. Polysaccharide extracted by hot water contains a large amount of protein. Sevag method, TCA method, neutral protease method and alkaline protease method were used to remove the protein. The deproerinization efficiency was 78.50%,56.56%,90.67% and 96.77% respectively, and the loss of polysaccharide was 56.50%,10.63%,7.95% and 9.80% respectively. It is clear to see that the application of protease method in deproteinizaiton was much more efficiency and had less loss of polysaccharide.BP was separated by DEAE Cellulose-52 column, The elution was performed by step-wise process using the same buffer containing different concentrations of NaCl: 0.1 mol/L, 0.3 mol/L , 0.5 mol/L and 2 mol/L, respectively. and three fractions were obtained under the concentrations of 0.1 mol/L, 0.3 mol/L, 0.5 mol/L, which were named BPⅠ,BPⅡand BPⅢ. The Sephadex G-100 column was applied for further purification. The result showed that Sephadex G-100 could remove the protein from BPⅠ,BPⅡand BPⅢeffectively , but there was some protein combine with BPⅠ, it may be a kind of glycoprotein. Ultraviolet spectrum analysis and freeze-thaw analysis showed that these fractions were purified polysaccharide, and named as BPSⅠ,BPSⅡand BPSⅢ.The content of sulfate was different amount different fractions, BPSⅢhad highest level of sulfate, the next was BPSⅡa nd the BPSⅠhad the lowest level of sulfate. The content of sulfate was also positive correlation with its purity. Gas chromatography analysis showed that the mainly monomers of BPSⅠa nd BPSⅡwas galactose, the BPSⅢalso contained some xylose except galatose. According to IR spectra, it could be confirmed that the ploysacchardes part of BPSⅠwas composed by 6-sulfate-β-D-galactose and 3, 6-anhydro-glaetose, BPSⅡa nd BPSⅢwere composed by 6-sulfurde–D-galactose, which did not contain 3, 6-anhydro-glaetose.Antioxidant activity in vitro of BP,BPSⅠ,BPSⅡand BPSⅢwas determined, the result showed that the IC50 on·OH was 4.98 mg/mL,1.22 mg/mL,13.86 mg/mL and 1.78 mg/mL respectively, the IC50 on DPPH was 0.70 mg/mL,1.05 mg/mL,0.58 mg/mL and 0.55 mg/mL respectively, the IC50 on liposome oxidation was 5.37 mg/mL,2.83 mg/mL,24.02 mg/mL and 1.60 mg/mL respectively, but there was no significant effect on the inhibition of O-2.