Synthesis,Characterization And Bioactivity Of Selenized Polysaccharide From Cordyceps Militaris

Selenium(Se), an essential trace element and a cofactor of a mass of Se-dependent enzymes, has received considerable attention due to its physiological functions. Selenized polysaccharides can combine the bioactivity of both the trace element and the polysaccharides. Polysaccharides is one of the main active ingredient of Cordyceps militaris. The main aims of this study was to optimize the reaction condition for the selenized Cordyceps militaris polysaccharide, to investigate the purification method for it,to elucidate the structure and to study the antioxidant and antitumor in vitro activity of this Selenized polysaccharide.The reaction was conducted by using Na2SeO3/HNO3 and BaCl2 as a catalyst with the assistance of an ultrasonic machine. In order to obtain the modified polysaccharide with the highest Se content and an ideal yield, the effects of the reaction temperature, the reaction period, the dosage of Na2SeO3 and the catalyst were investigated. The optimum condition were listed as follows: The dosage of Na2SeO3 (5mg/mL) 4 mL, temperature of 60℃,reaction period of 8h. Afterward, SeCPS-I and CPS-I were isolated by Sephadex G-100 column chromatography and ultra-filtration tube with molecular cut off weight of 100000 Da. Atomic fluorescence was used to measure the selenium content of the unmodified CPS-I and selenized SeCPS-I. According to the result, the Se content of SeCPS-I and CPS-I was measured to be 541.3 and 2.32μg/g respectively. Monosaccharide analysis, NMR,FT-IR analysis, periodate oxidation, Smith degradation methylation analysis and premethylation analysis were carried out to analyze the structure characteristics of SeCPS-I by comparing with CPS-I. The results indicated that CPS-I and SeCPS-I were composed of Glucose, Mannose and Galacose in the mole ratio of 1:14.51:1.18 and 1:9.91:0.94,respectively. α configuration was dominated in both CPS-I and SeCPS-I with few βconfiguration existed. In addition, the selenization was occurred at C-6. Results also showed that the percentage of (1→4) Gal and (1→4)Glc linkage which reported to be the backbone of the structure was higher in CPS-I than that of SeCPS-I. Changes were also indicated by rotation meter, congo red test, SEM and AFM, these changes showed that the selenization process had some influence on the way molecule intertwined with each other as well as their solution conformation of the polysaccharide.Furthermore, DPPH, hydroxyl, ABTS and superoxide radical were used as several radicals to examine and compare their antioxidant activity in vitro. Their anti-tumor activity in vitro were also investigated by comparing the inhibitory activity against the promotation of HepG-2 cells by using the MTT method. The results indicated that the selenization process could improve the antioxidant and antitumor activity of this polysaccharide under proper concentration.