Extraction,Comparison Of Antioxidant Activity And Preliminary Structure Of Polysaccharides From Dendrobium

Dendrobium is a perennial herb of Orchidaceae,which is a valuable traditional Chinese medicine in China.Polysaccharide is one of the most active ingredients in Dendrobium.It has always been the focus of research to find more active dendrobium polysaccharides and to explore the relationship between structure and activity.Studies have shown that the degradation,separation and purification of polysaccharides can improve biological activity.The degradation of polysaccharides has been reported in seaweed polysacchari des,but the structure and activity of degrading dendrobium polysaccharides as experimental materials have not been studied.In this study,the degradation,separation and purification,physicochemical properties,antioxidant activity evaluation and primary structure identification of Polysaccharides from Dendrobium officinale Kimura et Migo,Dendrobium nobile Lindl.and Dendrobium denneanum Rchb.f.var.denneanum?Kerr?Z.H.Tsi.were systematically studied.In order to provide a theoretical basis for the development and utilization of dendrobium polysaccharides.The main results are as follows:1.The crude polysaccharides DOP,DNP and DDP of Dendrobium were obtained by water extraction and alcohol precipitation.The crude polysaccharide were separated and purified by DEAE-52 cellulose chromatography column and Sephadex G-100 column to obtain dendrobium polysaccharide with relatively simple molecular weight range and different polarity,DOP-1,DOP-2,DNP-1,DNP-2,DDP-1,DDP-2.At the same time,the crude polysaccharide of Dendrobium was degraded by H₂O₂+VC,and the polysaccharide components DDOP,DDNP and DDDP with lower relative molecular weight were obtained.2.The anti-oxidation activities of 12 polysaccharide components of Dendrobium were compared in a concentration-dependent manner,and the active components or functional groups were different between different antioxidant activity indexes.DDOP has the best Fe²⁺chelation and ABTS+·scavenging power,DDDP has the best·OH scavenging power,and DDNP has good reducing power.3.DDOP is mainly composed of mannose,rhamnose,glucose,xylose and fructose.DDNP is mainly composed of mannose,glucose and fructose.DDDP is mainly composed of mannose,glucose and xylose.The molar ratios were 0.70:0.15:6.72:0.38:0.44,0.71:7.62:0.44,0.65:4.88:0.26,respectively.4.The molecular weights of three high antioxidant active polysaccharide fractions determined by HPLC-GPC were DDNP=16.4 kDa,DDDP=11.9 kDa,DDOP=11.8kDa.5.The structural analysis of the three polysaccharide components by infrared spectroscopy and nuclear magnetic resonance showed that they all contain characteristic absorption peaks of saccharide compounds,and have,acetyl,MeO and glucuronic acid groups.Substitution may exist on C2,C3,C4,C5 and C6.DDOP is a fragment of beta-configuration furan glycocyclic polysaccharide.DDOP is a?-configuration furanose polysaccharide fragment,DDNP is a?-configuration pyranose polysaccharide fragment,and DDDP is an?-configuration pyranose cyclic polysaccharide fragment having a triple helix structure.