Isolation And Structural Analysis Of Polysaccharide From Bupleurum Chinense

Bupleurum is a traditional Chinese medicinal plant.Its root is often used as medicine.It is mainly distributed in the northeastern part of China.It has the effects of soothing the liver and relieving depression.Polysaccharide is one of the main effective active ingredients in Bupleurum,which has many functions such as improving immunity,anti-inflammation and anti-tumor.However,structural characteristics of polysaccharides are still unclear.Therefore,polysaccharides of Bupleurum were prepared and their structures were analyzed in this thesis.Polysaccharide(WBCP)was extracted from Bupleurum by hot water and precipitated by ethanol,with the yield of 5.6%.The sugar content,uronic acid content,protein content and ash content of WBCP was 62.3%,19.2%,1.44%,and 19%,respectively.It mainly contains Glc,GalA,Ara,Gal and Rha,with molar ratio of 36.8%,25.7%,15.8%,11.1% and 4.5%,respectively.WBCP was fractionated by ion exchange chromatography,giving a neutral polysaccharide WBCP-N and an acid polysaccharide WBCP-A.WBCP-N was starch-like polysaccharide,which was not further studied in this thesis.WBCP-A was further purified by gel permeation chromatography,and a homogeneous fraction WBCP-A2 was obtained.Through monosaccharide composition,infrared spectroscopy and nuclear magnetic resonance analysis,it is speculated that WBCP-A2 was composed of homogalacturonan(HG),rhamanogalacturonan I(RG-I)and rhamanogalacturonan II(RG-II)type pectin.To further analyze their structures,WBCP-A2 was hydrolyzed by endo-polygalacturonanse.The hydrolyzed products were purified by gel permeation chromatography and four sub-fractions WBCP-A2 a,WBCP-A2 b,WBCP-A2 c and WBCP-A2 d were obtained.Nuclear magnetic resonance analysis,methylation analysis and enzymatic hydrolysis indicated that WBCP-A2 a was a RG-I type pectin,containing arabinan and type II arabinogalactan(AG-II).WBCP-A2 b contained RG-I type pectin,with arabinan,AG-II and type I arabinogalactan(AG-I)side chains.Minor highly-esterified HG domain was also detected in it.TBA assay and monosaccharide composition analysis indicated that WBCP-A2 c was mainly composed of RG-II type pectin,while WBCP-A2 d was galacturonic acid oligosaccharides produced by enzymatic hydrolysis.These domains were covalently linked.In summary,Bupleurum polysaccharide contains starch-like polysaccharide and HG,RG-I,and RG-II type pectin.HG accounts for a large proportion in acid polysaccharides and is partially esterified.These results provide useful information for biological activity analysis of polysaccharides from Bupleurum.