| Astragalus is one of the most commonly used Chinese medicine by the herbalist doctors in all ages, which has a long history of clinical application. The active ingredient APS has many kinds of pharmacological effects. The selenium polysaccharide, obtained by the organic synthesis of selenium and polysaccharides, is ester selenite with the chemical structure of 5-elements-ring composed of selenium and the adjacent two cis-hydroxyl on monosaccharide. As an organic selenium compounds, selenium polysaccharide give full play to the physiological activity of polysaccharide and selenium, so that the roles of both are coordinated and enhanced. That effectively improves the bioavailability of selenium, and their degree of the physiological function as a bio-essential trace elements. Compared with inorganic selenium, selenium polysaccharide reduces the toxicity and side effects greatly.This study was to research choosing Astragalus root as the research object, using water extraction to extract the crude astragalus polysaccharide, then removing the protein and pigment, purifying the crude astragalus polysaccharide through the column chromatography. Four kinds of purified APS were obtained. These APS were modificated by selenium, then the selenium polysaccharides with stronger medical effect were synthesized. The in vitro antioxidant activity was analyzed, which provides a theoretical basis and evidence for applying it as immunoadjuvant to the animal vaccine so as to enhance the immune efficacy of the vaccine.Experiment 1 The study was to research the methods of extraction and purification of the astragalus polysacchariedes. Polysaccharides were extracted by the traditional method of water extraction and alcohol precipitation from the Mongolia Astragalus roots. Firstly, ethanol precipitation was used to directly extract the crude astragalus polysacchariedes (APSt). Secondly, the components of APS40, APS50 and APS70 were extracted by alcohol precipitation sequentially. Then Trichloroacetic acid was used to removing the protein. After removing the pigment by the hydrogen peroxide, DEAE A-25 column and Sephadex G-75 column chromatography was adopted to further purify them. The results showed that each component of APS increased polysaccharide content after purification, and the protein content was decreased, which indicated that the method was feasible to improve the purity of polysaccharides.Experiment 2 The study was to research the selenium modified method for APS. Under the catalysising of the barium ion and hydrogen ion, polysaccharide compounds and selenous acid or selenium selenite set off a chemical reaction in acidic conditions, so selenium was modified into APS. With yields of products and the content of selenium as two indicators, orthogonal experimental was designed to optimize the best reaction temperature, the amount of Na2SeO3 and the reaction time.9 kinds of polysaccharides in 9 kinds of conditions were marked with seAPS-1, seAPS-2, seAPS-3, seAPS-4, seAPS-5, seAPS-6, seAPS-7, seAPS-8 and seAPS-9, whose selenium content was tested by atomic absorption spectrometry Fluorescence. With the best modification conditions concluded above, APSt,APS40, APS50 and APS70 were selenium modified and their selenium contents were determinated. The results showed that the highest selenium content was received when the reaction temperature was 70℃, the dosage of 5mg/mL Na2SeO3 solution was 4ml, and the reaction time was 8h.Experiment 3 The scavenging power for the the hydroxyl radical and superoxide anion and the total reducing power were researched between the Se-APSs and APSs, which reflected the strength of their in vitro antioxidant activity. The results showed that: comparing to the control, APSs could scavenge more hydroxyl radical and superoxide anion, and Se-APSs could scavenge more than APSs, the in vitro antioxidant activity of Se-APSs was stronger than APSs. The Astragalus antioxidant activity of Se-APSs performed positive correlation with the polysaccharide concentration and selenium content. |
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