Study On Methyl Esterification Sites Of HG Pectin From Schisandra Chinensis

Schisandra chinensis?Schisandra chinensis?Turcz.?Baill?is a plant of Magnoliaceae,Schisandra,which has the effects of reducing lung,cough,nourishing astringent essence,stopping diarrhea and stopping sweating.Water soluble polysaccharide is one of the effective components of Schisandra chinensis,especially pectin polysaccharides.Pectin is one of the main components of plant cell wall,and also a kind of complex biological macromolecule in nature.The physiological and pharmacological activities of different types of pectin are very different.Therefore,clarifying the structural charateristics of pectin is the basis of studying the activity and structure-activity relationship of pectin.In this study,we first prepared pectin polysaccharides from Schisandra chinensis,and then analyzed the structural characteristics of the main type HG pectin.The results are as follows:The DEAE-Cellulose ion exchange chromatography was used to classify the polysaccharide SCP of Schisandra chinensis,and the neutral sugar level and 0.5 M NaCl solution eluted from the distilled water were obtained for the pectin grade SCPA.Monosaccharide composition analysis showed that SCPA is composed of GalA,in addition to a small amount of Glc,Gal,Rha and Ara.The results of ¹³C NMR spectrum and TBA qualitative detection showed that SCPA was mainly composed of HG pectin domain and a small amount of RG-I and RG-II type pectin domains.Meanwhile,the results of ¹³C NMR spectra and FT-IR spectra showed that the HG domain in SCPA had a higher degree of methylation and did not have acetylation modification.In order to analyze the main HG domain in Fructus Schisandrae pectin,Endo-polygalacturonase M2?EC 3.2.1.15?was used to hydrolyse the total pectin SCPA.The products were classified by Sephadex G-50 gel chromatography column chromatography,and four fractions of SCPA-PG1,SCPA-PG2,SCPA-PG3 and SCPA-PG4 were obtained.The analysis of monosaccharide composition showed that SCPA-PG1 was a RG-I domain with larger molecular weight,SCPA-PG2 was a RG-II domain,SCPA-PG3 and SCPA-PG4 were oligosaccharide fragments produced by the degradation of HG type pectin.The HG oligosaccharide fragments were analyzed by first and two mass spectrometry by ESI-IT-MS respectively,and the location of methyl ester in HG oligosaccharide fragments was determined.A high purity HG pectin structure with GalA content above 90%was isolated and purified from the total pectin SCPA of Schisandra chinensis by chromatography.The structure model of HG pectin in Schisandra chinensis was preliminarily deduced by enzymatic hydrolysis and ESI-IT-MS.