Study On The Isolation And Purification Of Oligosaccharides From Dendrobium Officinale And Its Prebiotic Activities

Dendrobium officinale which belongs to the orchidaceae family dendrobium sw is a precious medicinal plant in China.The functions of anti-aging,anti-tumor,hypoglycemic,and enhancing body immunity can be attributed to the biologically active components in the Dendrobium officinale,including polysaccharides,alkaloids,polyphenol and so on.Oligosaccharides from Dendrobium officinale were isolated,and the characterizations as well as prebiotic activities were investigated.The main research results are as follows:1.The effects of solid-liquid ratio,time and temperature on the extraction of oligosaccharides were investigated.The extraction conditions were optimized by using response surfaces.The optimal conditions for extracting oligosaccharides were as follows: solid-liquid ratio 1:52,temperature 57 ℃ and time 85 min.The yield of oligosaccharides was10.13% under optimal water extraction conditions.The proteins,polysaccharides,and pigments in crude oligosaccharides were removed by Sevag method,alcohol precipitation,and activated carbon,respectively.An oligosaccharide named DOO1-1 was isolated by DEAE-52 anion cellulose column and Sephadex G-10 dextroan gel column.The content of total sugar and reducing sugar in Dendrobimu officinale oligosaccharide DOO1-1 did not change significantly in the simulated gastrointestinal fluid for 12 h which indicated that DOO1-1 possessed prebiotic characteristics.Scanning electron microscope images showed that the surface of oligosaccharide DOO1-1 was rough and tight.2.DOO1-1 with molecular weight of 2270 Da was purified by chromatography.DOO1-1 was mainly composed of glucose(64.960%),mannose(27.995%),and a small amount of glucuronic acid(2.815%),galactose(3.071%),arabinose(1.155%).The existence of β-glycosidic linkages(β-1,4)between the sugar units was confirmed by FTIR and NMR spectra.3.The antioxidant results showed that Dendrobium officinale oligosaccharide DOO1-1 had obvious scavenging ability of free radicals.The scavenging ability of DOO1-1 on ABTS,DPPH,and hydroxyl free radicals were 85.52%,74.09% and 72.84%,respectively.DOO1-1 could promote the proliferation of lactobacillus casei,Lactobacillus acidophilus,bifidobacterium bifidum and intestinal florai which was better than that of fructooligosaccharide.DOO1-1 could be utilized by these probiotics to produce short-chain fatty acids.The content of lactic acid and acetic acid were higher than that of butyric acid and propionic acid.The results suggested that Dendrobium officinale oligosaccharide DOO1-1 have potential prebiotic properties.