The Separation And Purification Of Sargassum Fusiforme Fucoidan And Structural Analysis Of Fraction SFF-32

Fucoidan is a natural marine source and rich in algae sugar and sulphate-based polysaccharides,with a wide range of biological activity.In recent years,the research on its structure-activity relationship has become a hot topic in the field of life and health.In this paper,the main experimental material of Sargassum fusiforme was collected in the Dongtou District of Wenzhou City,Zhejiang province and a systematic study was carried out on Sargassum fusiforme fucoidan SFF,including extraction,purification,structural characterization,biological activity,etc.The main results are as follows:(1)Dry and skimmed Sargassum fusiforme powder was separated by acid water leaching and calcium chloride precipitation,and then crude Sargassum fusiforme fucoidan(c SFF)was obtained by the treatment of repeated freeze-thaw and deproteinization.Then,according to the charge properties,the c SFF was fractionated by DEAE-cellulose column,and five fractions were SFF-1,SFF-2,SFF-3,SFF-4 and SFF-5.Further 8 homogeneous fractions were obtained by use of Sepharose CL-6B gel filter column,purified by molecular weight size.there were SFF-11,SFF-12,SFF-2,SFF-31,SFF-32,SFF-41,SFF-42 and SFF-5.(2)The fraction of SFF-32 wascharacterized by chemical methods(desulfurization reaction,esterification reduction and methylation analysis)and spectroscopy(FI-IR,NMR),and the results shown that SFF-32 was mainly connected by three types of connections:[?3)-?-L-fucp-(1?4)-?-D-Manp-(1?4)-?-D-Manp-(1?4)-?-L-Rhap-1?],[?3,4)-?-L-fucp-(1?4)-?-D-Manp-(1?3)-?-D-Glcp-(1?],[?-L-Xylp-(1?2,3)-?-D-Galp-(1?].(3)The advanced structural characterization results of the above eight homogeneous fractions were as follows: Scanning electron microscopy results shown that the surface morphology of the eight fractions was smooth,but there were some differences.The fractions SFF-11 and SFF-12 had similar appearances,all of which were irregularly flaky or elongated,and their structures were relatively dense,suggesting that the intermolecular repulsion is small.SFF-2 had a condensed and irregularly curled structure,indicating that it has a certain compliant structure.The two fractions obtained after SFF-3purification were SFF-31 and SFF-32,and their structures were completely different.SFF-31 was fibrous or flaky,with a wrinkled structure on the surface.The SFF-5 was in the form of a sheet or a short rod with different stacking levels.The fractions SFF-32,SFF-41 and SFF-42 had a certain repulsive force between the molecules.Congo red experiment and circular dichroism results shown that SFF-32 and SFF-41 had triple helix structure,while SFF-11 and SFF-2 had random coilstructure in aqueous solution,and SFF-12 had certain flexibility.(4)Furthermore,in vitro antioxidant activities of the above 8 fractions were evaluated by DPPH and hydroxyl radical scavenging assays.The results shown that each fraction had a certain degree of antioxidant activities,and the fraction SFF-42 with high sulfate content and moderate molecular weight shown the best antioxidant activities,and the DPPH· scavenging rate of SFF-42 was up to 62.61%.The present study provides scientific evidence on the influences of degree of sulfation and molecular weight of the fucoidan on antioxidant activities of S.fusiforme fucoidans.