Extraction, Purification And Biological Activity Of The Laminaria Polysaccharide Sulfate

The traditional methods to extract laminaria polysaccharide sulphate from Laminaria Japonica include the method of using hot water, enzyme and alkali, but all the three methods have the limitation. Using the method of hot water, we have to control the temperature to get to more than 70 centigrade, which takes a long time and wastes much power. The method of enzymolysis also needs a long time, and if we apply it to manufacture in the industry, it will need a great deal of enzyme, which is diseconomy. Most of the industries are extracting the laminaria polysaccharide sulphate by alkali, but this will reduce the biological function of the polysaccharide. Now it is important to find a new method to extract the laminaria polysaccharide sulphate, so we decided to use ultrasonic to extract polysaccharide.Firstly, we extracted the polysaccharide by traditional methods, and studied their physical and chemical characterization. Then the effect of five kinds of factors, which were the ultrasonic frequency, ultrasonic act duration, ultrasonic act time, solvent to solute ratio and pH, were investigated. The result of each experiment was applied to analyze the experiments of orthogonal design (L₉(3⁴)). Nine kinds of polysaccharide were extracted, the physical and chemical characterization of which were investigated. The results of all the experiment showed that the optimal condition for extraction of polysaccharides was A₂B₁C₃D₂ that was 1:30 solvent to solute ratio, 30 minutes action duration, 60℃ action temperature and natural pH.Compared the polysaccharide extracted by the best method of ultrasonic with the traditional methods, we found that the content of polysaccharide extracted by ultrasonic was almost same to that extracted by the hot water and enzyme, which was much higher than the alkali. The result of the viscidity study showed that molecular weight of most of the polysaccharide extracted by ultrasonic was smaller than traditional methods, which was proved by the experiment of ultra-filtration. When the membrane of MW100000 was used, about 40 percent of the polysaccharide extracted by ultrasonic passed the membrane, which is higher than the traditional methods. Gas chromatography suggested that all the polysaccharide contained fuc, xyl, man, gal and gal acid, and had no change. Molecular weight estimated by HPLC showed that there was little difference between all the polysaccharide extracted by different extracted methods. After studying the content of SO₄^2- in the polysaccharide, we found that the content of SO₄^2- extracted by ultrasonic was also higher than by the traditional methods, which reached 9%. While the content of SO₄^2- was connected with biological function, so we conferred that the biological function of the polysaccharide extracted by the new method should be better than the traditional methods. All the extracted polysaccharide could scavenge the hydroxyl free radical. The difference was that the scavenging rate of polysaccharide extracted by ultrasonic to hydroxyl free radical was higher than the others. All the polysaccharide except extracted by alkali could inhibit the growth of C6 cells.