Study On Intestinal Immunomodulating Activity Screening And Physicochemical Properties And Structural Characterization Of A New Polysaccharide From Dendrobium Chrysotoxum Lindl

This paper aimed at investigating the bioactive of intestinal mucosal immunity and the structural characteristics of the homogeneous fraction,isolated from Dendrobium chrysotoxum Lindl(DC).According to the guidance of intestinal mucosal immune evaluation experiments,the DCP-F4 was obtained by the procedure of extraction,separation and purification.In addition,the optimization of polysaccharide extraction method and the physicochemical properties was studied,which will lay the foundation for structure-activity relationship of Dendrobium C Lindl polysaccharides.The obtained results were as follows:(1)Tlle extraction of homogeneous polysaccharide The ethanol extract(DCE-A 7.48%)was removed from the dry powder,and the DCP was obtained from the residue by 80% ethanol extraction(DEC-B 7.93%)followed by ethanol precipitaton(DCE-C 7.14%)then was processed by deprotein(DCE-D 4.67%)and dialyzation(DCP 3.72%).Extracts was selected by intestinal mucosal immune activity evaluation in vitro.DCP-2 was islated from DCP by gradient EtOH precipitation.The polysaccharides were successfully purified by chromatography on DEAE-cellulose-52 and Sephadex G-100 columns.DCP-F4 was the component which exerted the most potent intestinal mucosal immune modulating activity.(2)The intestinal immunomodulating activity of polysaccharides These fractions of DC are both potential modulators in intestinal mucosal immunity.Compared to the control,the prolification of bone marrow cells was increased by 3.3% to 89.0% with administration of crude extract.The high content of carbohydrates was acquired by stepwise isolation procedure,which displayed more potent activity.The more significant increase of bone marrow cells stimulated by 60% EtOH precipitation polysaccharide(DCP-2)from 44.8% to 91.4% than the other two components.Though the further purification,DCP-W and DCP-F4 was islated with strong intesitinal immunity.The cell proliferation of DCP-W group was increased by 56.1% to 95.7% and DCP-F4 was significantly higher than the control(2.136 fold).(3)The physicochemical properties and structural features of DCP-F4 The results revealed that the content of carbohydrates and uronic acid is 94.32%,1.85% in DCP-F4,respectively,with a relative molecular weight of 1.37 � 104 Da and polydispersity index of 1.1495.FT-IR showed the typical strentching vibration in the sugar rin.The qualitative DSC study also proved the homegeneity and stability with only a heat absorption peak at 122? and a heat release absorption peak at 316??Sugar analysis reavealed that DCP-F4 was composed of Xyl?Man?Glc in molar ratio of 1:7:16.Combined the methylation analysis results with NMR spectroscopy,a preliminary structure of DCP-F4 was found to have a backbone of 1,4-Linked Manp residues and 1,4-Glcp residues,with branches at 1,4,6-Linked Manp.The side chain composed of terminal Glcp and terminal Xyl.