Isolation,Purification And Structure Identification Of Polysaccharide From Fermented Dendrobium Officinale

Dendrobium officinale is a perennial herb,belonging to the Orchid Dendronium,which is mainly distributed in southern China.As the main active ingredient,polysaccharides have strong biological activity.After fermentation by probiotice,the molecular weight of polysaccharides changes,and the corresponding biological activity function also changes.Objective: A polysaccharide was purified in this paper,which was acquired from the fermentation broth of Dendrobium officinale Kimura er Migo.This article aims to investigate the structural features and bioactivity of this polysaccharide.Methods: Single factor experiment was conducted to explore the effects of extraction temperature,time and ratio of material to liquid on the polysaccharide yield of Dendrobium officinale fermentation.Response surface experiment was conducted to determine the optimal extraction process of Dendrobium officinale fermentation polysaccharide.The polysaccharides were purified by chromatographic method.The structure of the purified polysaccharides was characterized bv various modern instruments,combined with the complex carbohydrate research center(CRCC)database mode of polysaccharide glycosidic bond links compare analysis,provide a reference basis for its structure analysis.Results:(1)Determination of extraction conditions of polysaccharide from fermented Dendrobium officinale.Response surface method was used to optimize the extraction experiment of polysaccharides.When the liquid-solid ratio was 60:1 m L/g,the extraction time was 40 min,and the extraction temperature was 130 °C,the extraction rate of crude polysaccharides was 17.8% ± 0.02%.(2)Determine the physicochemical data and structure of components DOP-1 and DOP-2.Two major polysaccharide components,DOP-1 and DOP-2,were separated by two-step column chromatography after deproteinization of crude polysaccharide.The molecular weights were 447.48 KDa and 523.07 KDa respectively detected by HPGPC.Component DOP-1 consists of galactose,glucose and mannose in a ratio of 1:1.79:6.71.Methylation and and NMR spectroscopic analysis indicated that the backbone of DOP-1 is: →4)-α-D-Glcp-(1→4)-α-D-Manp-(1→4)-α-D-Manp-(1→4,6)-α-DManp-(1→,itse repeating units were also preliminarily setablished.(3)Antioxidant activity of DOP-1 and DOP-2.In the range of experimental concentration,DOP-1 and DOP-2showed a certain scavenging ability to hydroxyl radical and DPPH radical,and the ability was concentration dependent.Conclusion: Polysaccharides were extracted from the fermentation liquid of Dendrobium officinale.Its molecular weight is 447.48 KDa.The polysaccharide is composed of a large amount of mannose and a small amount of glucose and galactose.The structure of the polysaccharide was characterized,and the main glycosidic linkage was as follows: →4)-α-D-Glcp-(1→4)-α-D-Manp-(1→4)-α-D-Manp-(1→4,6)-α-D-Manp-(1→.The results showed that DOP-1 not only had better scavenging ability to ·OH,but also had better chelating ability to ferrous ions,which indicated that it had better antioxidant potential.