Structural Characterization And Biological Activities Of Polysaccharides From Dendrobium Moniliforme (L.)Sw

The Chinese crude drug 'Shi Hu' is prepared from the dried stems of Dendrobium species, and has been used as a tonic and an antipyretic. Much attention has been focused on its basic components and pharmacological activities. Polysaccharide is the major active constituent from Dendrobium plant. Dendrobium moniliforme (L.) Sw, from which the Chinese drug was most originally prepared, was studied in this paper. After ingredient contents and distributions in different part of three Dendrobium species were researched, water-soluble polysaccharides were extracted isolated and purified from Dendrobium moniliforme (L.) Sw (DMP). The chemical properties and structural features of main DMP fractions were investigated. Some pharmacological action and mechanisms were also investigated here. The correlation between bioactivities and the conformation of polysaccharides was discussed. The main results indicated as follows:Bioactivity constituents and distributions in Dendrobium plantsDendrobium moniliforme (L.) Sw and Dendrobium officinale Kimura et Migo contained very high total polysaccharides and water-soluble polysaccharides. Comparatively, Dendrobium hancockii Rofle plants had a high content of total polysaccharide, but its water-soluble polysaccharide content was relatively lower, only about 25%~30% of that of die two formers. Both Dendrobium moniliforme (L.) Sw and Dendrobium officinale Kimura et Migo species contained very high alkaloids. Contrarily, it was very low in Dendrobium hancockii Rofle plants. Alkaloid distributions in different part of these three Dendrobium species were all the same, from upper-stem, root, middle-stem to lower-stem, alkaloid contents were decreased in turn. Contents of mineral elements were high in Dendrobium moniliforme (L.) Sw and Dendrobium hancockii Rofle plants with similar distribution pattern.Influence of drying process on Dendrobium ingredientsContents of ingredients in Dendrobium moniliforme (L.) Sw were influenced by drying process. The total polysaccharide in D. moniliforme plant dried by sunlight was lower thanthat dried by fire at a high temperature. About 6.1% original polysaccharide was lost, and polysaccharide contents in different part of D. moniliforme were came to equaJ. Whereas, gross contents of alkaloid in D. moniliforme dried by different procedure had not changed, except to its distribution in different part. With regard to Dendrobium polysaccharide constituent, the ideal drying process of Dendrobium species plants after harvesting was dned by fire at a high temperature and desiccated at a temperature of 60 Extraction isolation and characterization of polysaccharides from Dendrobium moniliforme (L.) S\vDried powder of uncultivated Dendrobium moniliforme was extracted for 60min with 50癈 water . the weight of which is 20 times as much as that of powder. The extraction ratio of " D. moniliforme" polysaccharides was over 94%. The clear filtrate was concentrated under vacuum. Eight polysaccharide fractions, named as DMPla-1, DMPla-2, DMP2a-l. DMP3a-l, DMP4a-l, DMP5a-l. DMP6a-l and DMP7a-l, respectively, were isolated and purified with column chromatography on DEAE-cellulose. Sephacryl s-4(H) HR, Sephacryl s-200 HR and Sephadex G. Among which, DMPla-1, DMP2a-l, DMP4a-l were major constituents.DMPla-1 was judged to be homogeneous by high performance gel permeation chromatography. Its physicochemical properties and structural feature was elucidated by modern analytical techniques such as TLC. GC. UV. IR and Penodate Oxidation. Experiment results demonstrated that DMPla-1 was a glucomannan contained with a 1: 4.798 glucose-mannose ratio. The ultraviolet and infrared spectra analyses revealed that the DMPla-1 existed acetyl group in its molecular structure. Periodate Oxidation analysis indicated DMPla-1 contained 0(1-"4 or 1-2. 1-3. 1-6) glycosidic bond, appeared in the molar proportion of 23.59:8.75:1.DMP2a-l and DMP4a-l were protein-bound polysaccharides, with the molecular average-weight (M\v) 6289. 3049, respectively. DMP2a-l was composed of...