Isolation,purification and structural characterization of polysaccharides from Euodiae fructus
Euodiae fructus was used as raw material to separate and purify the crude polysaccharides of Euodiae fructus ex-tracted by hot water and ethanol precipitation,with the structure of purified components being characterized.Firstly,the decolor-ization method was determined based on the polysaccharide retention rate,decolorization rate and molecular weight distribution.Secondly,EFP was fractionated by gradient ethanol precipitation to obtain the purified polysaccharide fraction named EFP-20.Colorimetric assay,high-performance gel permeation chromatography(HPGPC),high performance anion exchange chromatog-raphy coupled with pulsed amperometric(HPAEC-PAD),methylation combined with gas chromatography-mass spectrometry(GC-MS)analysis and NMR spectroscopy were conducted to reveal the structural features including chemical composition,mo-lecular weight and linkage patterns,etc.The result indicated that activated carbon had the best decolorization effect on Euodiae fructus rutaecarpa polysaccharides,with a decolorization rate of 68.74％,and the retention rates of neutral sugar and uronic acid were 94.26％and 91.79％,respectively.After gradient ethanol precipitation,the molecular weight of the obtained polysaccha-ride,EFP-20,was 1.78× 107 Da,mainly composed of Rha(20.83％),Ara(23.16％),Gal(31.52％)and GalA(23.64％).Meth-ylation analysis indicated that the main glycosidic linkages included T-Arap(20.99％),2,4-Rhap(21.82％),1,4-Galp(11.05％)and 1,2-GalpA(14.33％)and 1,4-GalpA(11.05％).Combined with NMR analysis,EFP-20 was deduced as pectin,containing type I rhamnogalacturonan(RG-I)structures,with the major chain composed of α-1,4-GalpA and α-1,2,4-Rhap re-peating unit and branched at C-4.This study,focusing on the isolation and structural characterization of the polysaccharide from Euodiae fructus,would provide theoretical basis and data for development and utilization of essential resources from Traditional Chinese Medicine and their related functional products.
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