| The Onchidium struma was considered as a tonic of high nutritional value in the coastal cities, it had a long history of edible. At present the domestic and international research about O. struma were mainly concentrated in the classification system,biological characteristics and nutritional value, but study on the O. struma polysaccharide was relatively few. This paper studied on the extraction of polysaccharide of O. struma,and optimizing the extraction process; separation and purification coarse polysaccharides using column chromatography; analysis of its physical and chemical properties and chemical structure; the antioxidative activity of two kinds of polysaccharide obtained though different drying methods, which provided a theoretical basis for the polysaccharide in health food and pharmaceutical industry industrial production and development of O.struma.Onchidium struma polysaccharides was extracted by the traditional hot water extraction method. The effects of extraction temperature, extraction time, ratio of liquid to raw material on the extraction yields of OSP were investigated by using single factor Experiments. Process of extracting polysaccharides from O. struma was optimized by response surface methodology. The experiments were designed by Box-Behnken, and the data was analyzed by Design-Expert 8.05 software. On the basis of the analysis of regression equation, determination of factor effect of extracted polysaccharide was conducted by the extraction rate of polysaccharide served as response value. The influence sequence on the polysaccharide was as follows: extraction temperature >solid-liquid ratio > extraction time. The optimum extraction conditions were: extraction time of 30 h, extraction temperature at 92 ℃, and liquor-to-material ratio of 1:29 g·mL-1.Under optimum conditions, the leaching rate of O. struma polysaccharide was 9.206 %.Gray polysaccharides of Onchidium struma were obtained from the extract by the hot water extraction, evaporation and concentration, sevag method deproteinized,dialysis to removal small molecules, ethanol precipitation, acetone and petroleum ether washing and freeze drying. The isolation and purification of O. struma polysaccharide was accomplished by DEAE-52 cellulose and Sephadex G-200 column chromatography.Three kinds of polysaccharide, OSP-1, OSP-2 and OSP-3 were obtained by DEAE-52 cellulose column using phenol- sulfuric acid method to tracking and detection. The physical and chemical experiment showed that three polysaccharides are dissolved in water and insolubled in organic solvents; they are typical non-starchy carbohydrate without monosaccharides and polyphenols. OSP-2, OSP-3 were free of proteins and nucleic acids while OSP-1 contained trace amounts of protein after UV detection, three polysaccharide have a similar absorption peak which were furan polysaccharides by infrared spectroscopy. OSP-1, OSP-2 and OSP-3 is purificated and tested the purity by Sephadex G-200 column chromatography, The results show that OSP-2 and OSP-3were single purified components, OSP-1 consists of two components which have similar molecular weight, collecting main component OSP-1b for following-up study.Using GC-MS find that OSP-1b is consist of at least 4 kinds of polysaccharides,respectively, Rhamnose, Xylose,Arabinose and Mannose. 1H NMR spectra showe that OSP-1b has alpha- and beta- configuration of the glycosidic bond; 13C-NMR analysis showed that OSP-1b has 2 alpha- configuration of the anomeric carbon.The polysaccharide of Onchidium struma was extracted by using traditional hot water extraction and alcohol precipitation method, the influence of vacuum freeze drying and oven drying on the antioxidant activity of polysaccharides was investigated.The ant-ioxidant activities of the polysaccharide was evaluated by scavenging DPPH free radical, hydroxyl free radical, surperoxide anion radical and sodium nitrite, the total reducing capacity of polysaccharide was studied by spectrophotometric method. The results showed that the scavenging effect of freeze dried polysaccharide was stronger than the oven dried polysaccharide, the IC50 of scavenging activities against DPPH free radical, hydroxyl and sodium nitrite were 4.14 mg/m L, 2.96 mg/m L and 2.05 mg/m L,which showed a active relationship with polysaccharide concentration, but the polysaccharide had minor scavenging effect on surperoxide anion radical, and thereducing capacity was weak. The antioxidant activity of two polysaccharides were weaker than VC under the same concentration. |
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