Effects Of Extraction Temperature On Physicochemical Properties And Intestinal Mucosal Immune Activities Of Polysaccharides From Dendrobium Huoshanense

In this paper, a valuable traditional Chinese herbal medicine Dendrobium huoshanense was employed to investigate the effects of extraction temperature on the extraction efficiency, physicochemical properties and intestinal mucosal immune activities of polysaccharides. A homogeneous fraction HPS from D. huoshanense polysaccharides was successfully labeled with fluoresceinamine, which was used to explore the distribution of HPS in intestinal mucosal system.Fitting the ratio of material to water at1:3(m/v) and extraction time for2h with different extraction temperature changing from40℃to100℃, four crude polysaccharides were obtained from D. huoshanense with hot water extraction. The extraction yield of crude polysaccharides increased significantly with the enhancement of extraction temperatures. HPLC profiles showed there were two fractions with different molecular weights existed in crude polysaccharides of D. huoshanense. The proportions and molecular weights of higher molecular weight (HMW) polysaccharides decreased with the increment of extraction temperature, while the proportions and molecular weight of lower molecular weight (LMW) polysaccharides increased. Fractionation of crude polysaccharides using DEAE-cellulose anion exchange column gave two fractions, and the fractions eluted with1M sodium chloride (HPSS) consisted of totally HMW polysaccharides. HMW polysaccharides were composed of Gal, Glc, Ara, Man and Rha with almost constant ratio, and the configuration of sugar residues was β-configuration. HMW polysaccharides were with poor thermal stability, and tended to degrade with heat. The primary compositions of fractions eluted with distilled water (HPSW) were LMW polysaccharides, which were mainly composed of Glc, and certain amount of Gal, Man and Ara; the configuration of sugar residues was a-configuration. LMW polysaccharides were stable with heat, and the proportions increased with the enhancement of extraction temperatures. Thus, the effects of extraction temperature on the physicochemical properties of polysaccharides from D.huoshanense were attributed to the change of proportions of these two fractions with different characters. Crude polysaccharides and their two fractions all exhibited potent intestinal mucosal immune activities, and the activities all decreased with the increment of extraction temperatures. The activities of HPSS were stronger than crude polysaccharides and HPSW, thus the HMW polysaccharides were the main active compositions, and the activities decreased with degradation of high extraction temperature.A homogeneous fraction HPS was separated with gel permeation chromatography from crude polysaccharides of D. huoshanense. HPS showed potent intestinal mucosal system immunomodulating activity, which could promote the proliferation of bone marrow cells stimulated by Peyer’s patch cells conditioned medium. HPS was successfully labeled with fluoresceinamine via CNBr-activation. Fluorescent labeling had no significantly effect on the intestinal immune activity of HPS, nor induced cytotoxicity. HPS could enter intestinal mucosal system and bind to certain cells in Peyer’s patches.