| Dendrobium officinale is a precious Chinese herbal medicine.Pharmacological studies have shown that Dendrobium officinale polysaccharide has a variety of medicinal effects.Therefore,the research on the polysaccharides in Dendrobium officinale is of great significance.This subject mainly uses water extraction and alcohol precipitation to obtain crude polysaccharides from Dendrobium officinale stems,and optimizes the extraction conditions of Dendrobium officinale polysaccharides through a combination of uniform design and orthogonal design experiments.The temperature is 60℃,the time is 2h,and the liquid-to-material ratio is 70:1,the extraction rate can reach 44.89%.Next,we try to use high-speed countercurrent chromatography to separate and purify the crude polysaccharides extracted from Dendrobium officinale.Orthogonal experiments are carried out with the partition coefficient as the index,and the most suitable solvent system for Dendrobium officinale polysaccharides is 15%Mg SO4-12%PEG600-73%H2O（w/w/w）,the purity of refined polysaccharides from Dendrobium officinale can be determined to 92.19%by phenol-sulfuric acid method,indicating that the purification effect is ideal.Then,the preliminary identification of the structure of the purified polysaccharides from Dendrobium officinale shows that the molecular weight is 1025171Da.It is composed of Glucose and mannose,and the molar ratio is 1:3.219.Infrared spectroscopy and NMR spectroscopy preliminarily determine that the polysaccharide of Dendrobium officinale is aβ-glycosidic pyran polysaccharide compound.Finally,a comparative study on the antioxidant properties of crude polysaccharides and purified polysaccharides of Dendrobium officinale was carried out.It was found that both polysaccharides had scavenging ability on three free radicals,but the refined polysaccharides had better effects,indicating that the purity of polysaccharides had an impact on the antioxidant properties. |
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