Abstract: In this study, the deproteinization and structural characterization of the polysaccharides extracted from Dendrobium officinale Kimura et Migo grown in Huoshan county of Anhui province were investigated. Three protein removal methods: the Sevage method, enzymatic hydrolysis and their combination were comparatively evaluated in terms of protein removal and polysaccharide loss rates. The combined method was found to have the highest deproteinization efficiency, yielding 81.58% protein removal and 15.63% polysaccharide loss. After purification of the polysaccharides by successive DEAE-cellulose-52 and Sephadex G-100 column chromatography, an active fraction named as DOPA-1 was obtained. By using UV spectroscopy and high performance liquid chromatography (HPLC), the polysaccharide DOPA-1 was confirmed to be homogeneous. Moreover, DOPA-1 was mainly composed of mannose, glucose and galactose as revealed by GC analysis, with a molar ratio of 1:0.42:0.27. IR spectroscopy and Cango red test indicated that DOPA-1 contained β-D-mannopyranose and possessed a triple-helix conformation.

Key words: Dendrobium officinale polysaccharide, removal of protein, purification, structural analysis