Extraction, Isolation, Structure Identification And Antioxidant Research Of Brasenia Polysaccharides

In this study,Brasenia schreberi polysaccharides were extracted by water extraction and alcohol precipitation.The chemical composition of 7 samples,namely major leaf(M-BS),tender leaf(TL-BS),stem(TS-BS),their extracts(M-BSP?TL-BSP and TS-BSP)as well as external mucilage based gel of B.schreberi sample(G-BS)were investigated in this study.The scavenging effect of hydroxyl radical and DPPH,ABTS radical were analyzed.G-BS had highest content of polysaccharides and polyphenols among all samples.Therefore,G-BS sample was selected for membrane ultrafiltration.The component,which is with molecular weight less than10 million Da,was analyzed with GC-MS,SEM,DSC and NMR to investigate the advanced and primary structures of G-BS polysaccharides.This study provides a theoretical basis for the rational development and utilization of polysaccharides from Brasenia schreberi.The main results were as follows:(1)G-BS samples contained the highest TCC(589.11±11.07 mg/g)and TPC(175.97±5.13 mg/g),while it had relatively low·OH(IC50=3.42±0.12 mg/g),DPPH(IC50=4.39±0.24 mg/g)and ABTS free radical(IC50=1.66±0.05 mg/g)scavenging activity.Principal components analysis(PCA)showed that mucilage covered Brasenia schreberi was significantly different from the plant itself.Distinct from other polysaccharide samples,galactose(61.56±3.29 mg/g),fucose(36.45±0.68 mg/g)and arabinose(27.08±0.27 mg/g)were three top abundant monosaccharides in G-BS sample.G-BS were selected for further analysis.(2)Three components of G-BS were obtained by ultrafiltration with three different ultrafiltration membrane(PK100,PK50 and PK10).Components of PK100(CG-BS)had highest antioxidation effects among others.Therefore,we used CG-BS for further purification.Four components,namely CG-BS-0?CG-BS-1?CG-BS-2?CG-BS-3,were obtained by DEAE-Sepharose Fast Flow weak anion exchange column chromatography.CG-BS-1 were selected and purified by Sephacryl S500dextran gel column,after which pure component CG-BS-1a was obtained.After freezen-dry,CG-BS-1a was used for structure analysis.(3)Full UV spectroscopy scanning showed that CG-BS-1a contained neither protein nor nucleic acids.HPLC analysis showed that relative molecular weight of CG-BS-1a was 1.614×10~6 Da.After acetylation,the GC-MS analysis showed that D-galactose were the main monosaccharides of CG-BS-1a.IR analysis showed that CG-BS-1a might be a kind of L-d-pyranose type galactose.Further analysis of one or two-dimensional NMR showed that CG-BS-1a might be an acidic polysaccharide and mainly composed of?-1?6-linked.Futhermore,differential scanning calorimetry(DSC)and scanning electron microscope(SEM)analysis showed that CG-BS-1a had good stability in the temperature range of 30-200?and the molecular structure was mainly reticular with tight bindings.