Purification And Structural Analysis Of The Pectins From Lobelia Chinensis Lour.

Lobelia chinensis Lour.belongs to Platycodontidae,which has the functions of clearing away heat and toxic material,promoting diuresis and eliminating swelling.Polysaccharide is the main water-soluble substance in Lobelia chinensis Lour.,which has immune and anti-inflammatory activities.At present,the structure analysis of polysaccharides from Lobelia chinensis mainly focuses on the total polysaccharides and neutral polysaccharides,there are few studies on acidic polysaccharides（pectins）from Lobelia chinensis Lour.,It hinders the study of structure-activity relationship of the pectins from Lobelia chinensis Lour..In this thesis,the pectins from Lobelia chinensis Lour.were systematically purified and their structures were analyzed.The finding results are as follows:The polysaccharides were extracted from Lobelia chinensis Lour.by hot water extraction and ethanol precipitation,which were referred to as WLCP,the yield was 9.5%.WLCP contained 55.4%total carbohydrates,19.1%uronic acid,2.9%protein and 14.5%ash.WLCP mainly contained glucose（Glc 26.5%）,galacturonic acid（Gal A 25.9%）,galactose（Gal 17.0%）and arabinose（Ara 13.1%）.The Lobelia chinensis Lour.neutral fraction WLCP-N and pectin fraction WLCP-A were obtained by ion-exchange chromatography,the yield of WLCP-N and WLCP-A were 62.8%and 9.5%respectively.WLCP-A was further fractionated by ion-exchange chromatography,and four pectin fractions with relatively uniform charge distribution were obtained:WLCP-AH,WLCP-A2,WLCP-A3 and WLCP-A5.WLCP-A2 and WLCP-A3were further fractionated by gel chromatography,and four pectin fractions with relatively uniform charge and molecular weight distribution were obtained:WLCP-A2a,WLCP-A2b,WLCP-A3a and WLCP-A3b.Among them,WLCP-A2b and WLCP-A3b were the main pectin fractions in Lobelia chinensis Lour..Infrared spectra and ¹³C nuclear magnetic resonance spectra analysis were combined to characterize the structural features of WLCP-A2b and WLCP-A3b,it was speculated that both of them contained Homogalacturonan（HG）,Type I Rhamnogalacturonan（RG-I）and Type II Rhamnogalacturonan（RG-II）.WLCP-A2b and WLCP-A3b were hydrolyzed by endo-polygalacturonanse,the fragments were analyzed by HPLC,NMR and methylation analysis.The results showed that the contents of HG/RG-I/RG-II in WLCP-A2b and WLCP-A3b were0.2:1.5:1 and 1.3:2.8:1,RG-II existed in the form of monomer and dimer in WLCP-A2b and WLCP-A3b,RG-I was the main domain of two pectin fractions.The content of side chains of RG-I domains in WLCP-A2b（WLCP-A2b-1）was high,the main chains and side chains were highly branched,and the side chains contained type II arabinogalactan（AG-II）,arabinan and galactan.The content of main chains of RG-I domains in WLCP-A3b（WLCP-A3b-1）was high,the main chains and side chains were in low branching degree,the side chains contained galactan,AG-II and arabinan.The RG-I domains in WLCP-A2b were further enzymolyzed by RG-I lyase,the fragments were analyzed by HPLC,NMR and methylation analysis.The results showed that there was highly branched AG-II with high molecular weight in WLCP-A2b-1,which couldn’t be enzymolyzed by RG-I lyase;WLCP-A2b-1 contained regions with the features of highly branched main chains and various side chains（arabinan,galactan and AG-II）;WLCP-A2b-1 also contained regions which connected with short side chains,the short side chains were composed of（Ara）_x=0⁷and（Gal）_y=0³,the regions could be enzymolyzed by RG-I lyase because the main chains of them were in low branching degree.In this thesis,the structural characteristics of pectins from Lobelia chinensis Lour.were studied in detail,the results provide a theoretical basis for further investigation on structure-activity relationship and the development and utilization of Lobelia chinensis Lour.pectins.