Studies On Optimization Of Extraction And Antioxidant Activity Of Dendrobii Polysaccharides From The Root Of Dendrobium Candidum

Dendrobium candidum species as traditional Chinese herbs has been used for centuries. In many studies, polysaccharides from Dendrobii plants were found to be the main active components. Nowadays, the most important part of development and utili-zation is the stems of D. candidum, but few studies on its roots. In view of D. candidum being a valuable traditional Chinese medicine and its resource shortage, the systematic research on the polysaccharides from the roots of D. candidum is very significative, and the scientific application in medicine and food will be provided of it.In this paper, the research object is the Dendrobii polysaccharides from the roots of D. candidum. It was extracted by hot water and separated by ethanol to get different polysaccharide fractions. On the basis of the single factor, the response surface methodology was applied to optimize the main extraction conditions. The results showed that all effects about extraction time, feed-water ratio and extraction temperature were significant on the extraction rate of polysaccharides. Obvious correlation was found to be existed between extraction time and extraction temperature. The optimal extraction time was50min and the optimal feed-water ratio was1:14and the optimal extraction temperature was100℃. Under these optimized conditions, the extraction rate of polysaccharides was6.10%, the practical extraction rate was6.05%, which is highly fitting with the model.The Dendrobii polysaccharides were obtained by the optimized conditions of the water extraction, the yield of which was10.3%。Three fractional polysaccharides were collected by a series of operations as classification of ethanol precipitation, Sevag method removing proteins, etc. After ethanol fractional precipitation in concentration of30%,50%and75%ethanol aqueous solution, totally three parts, for CK-1, CK-2, CK-3, the yield of which was3.95%,1.42%,2.04%.Determination of antioxidant activity of polysaccharides extraction contains classification of ethanol precipitation of crude polysaccharide from CK-1, CK-2, CK-3, and contains determination of four antioxidant systems, namely superoxide anion clearance, DPPH radical scavenging rate, hydroxyl radical scavenging rate, and Fe2+chelating capacity. The results show that about superoxide anion scavenging rate, DPPH radical, hydroxyl free radical scavenging rate, and Fe2+chelating capacity, in three fractional polysaccharides, the most antioxidant capacity is CK-2、CK-3、CK-1、CK-1, resepectively, and scanvenging rate has reached66%(3.2mg/ml),79%(2.0mg/ml),73%(2.0mg/ml),88%(2.0mg/ml). Results showed that different polysaccharide fractions had strong antioxidant activities in dose-dependent manner in four antioxidant systems, and there is a certain dose effect relationship. All the above-mentioned aim will be beneficial for the systematic production and application of D. candidum. Ad...