| Striga asiatica (L.)O.Ktze which belongs to the Scrophulariaceae plant is used as medicine in some area.According to the reports it has an important medicinal functions sush as anorexia, nyctalopia, hepatitis, pediatric drug etc. In this paper, extraction, isolation and purification, structure of polysaccharide from Striga asiatica (L.)O.Ktze were studied and investigated using two assays in vitro, including scavenging abilities on DPPH and hysroxyl radicals power. Water-soluble polysaccharide was isolated from Striga asiatica (L.)O.Ktze with the method of water-dissolving and ethanol-precipitating.With the univariate and orthogonal experiments the optimization condition was confirmed solid-to-liquid was1:18,temperature was80℃,time was2.5h.The yield of polysaccharide is10%.DJP which was deproteinized and decolorized was isolated and purified using DEAE-SephadexTM-25.three polysaccharide DJP1, DJP2, DJP5were obtained. Then DJP1, DJP5were purified further by SephadexTMG-100and got DJP1*and DJP6respectively. HPLC producing a single symmetrical peak indicated that each of them was homogeneous and their molecular weight were DJP1*:14852,DJP6:11207.The Water-soluble polysaccharide DJP6has been analyzed by PC and GC, it was composed of Rha, Ara, Xly, Man, Gal, Glc, GalA;its molar ratio is Rha:Ara: Xyl:Man:Gal:Glc=1.0:0.95:0.2:0.35:0.38:1.1. DJP1*was investigated by IR,UV,GC,periodate oxidation, Simth degradation, methylation and GC-MS analysis,NMR spectroscopic methods to confirm its composition and the number of suger residues, form of the glycosy linkage.DJP1*was a neutral polysaccharide and composed of Rha,Ara,Xly,Man,Gal,Glc; its molar ratio is Rha:Ara:Xyl:Man:Gal:Glc=1.0:2.0:0.4:0.5:0.85:2.5.And the periodate oxidation, Simth degradation, methylation and GC-MS analysis showed that the main chain was made up of β-(1'3) Ara, β-(1'4or1'5) Ara and on average there were5branches among9main chain residues; β-(1'6) Gal, on average there were2branches among5main chain residues; The side chain was composed of β-(1'4or1'5)-Rha and (1'6、1'4、1'2)-Glc.The terminal residue was composed of Ara, Man,Gal and Glc. With the NMR analysis, it is showed that most of the suger residue were existed as β-configuration.The scavenging rates of the DJP6on hydroxyl, DPPH radicals were67.3%,28.9%, at polysaccharide concentrations of2.5mg/L,2.0mg/L, wheteas with vitaminC at similar concentrations with polysaccharide, the scavenging rates were95.0,80.1%,respectively. |
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