The Purification,modification And Biological Activities Of Polysaccharides From Ulva Fasciata

Ulvafasciata is a green alga which has been proven to be rich sources of structurally diverse bioactive compounds with valuable biomedical potential.In this paper,the extraction,desulfurization modification,biological activity and primary structure of polysaccharides from Vlva fasciata were systematic studied.The microwave assisted extraction conditions for Ulva fasciata polysaccharides were optimized on the basis of response surface methodology.The optimal extraction conditions were microwave power of 400 W,extraction time of 33 min,the ratio of water to material 25(mL/g),while the extraction rate reached 16.37%.The polysaccharides were separated into three different components by ultrafiltration:UFP1(Mw<10 kDa)?UFP2(10 kDa<Mw<100kDa)?UFP3(Mw>100kDa).The three UFP fractions had partial desulfurization by solvolytic desulfation respectively and the main physico-chemical properties were compared.Results showed that UFPs was a kind of acidic polysaccharides containing sulfate and uronic acid.The main component in UFP2,DS-UFP2,UFP3 and DS-UFP3 was total sugar,while the sugar in UFP1 and DS-UFP1 was relatively lower.The uronic acid content in different fractions had great diversity.The FT-IR spectra showed the main chain of the polysaccharides was complete.The partial desulfated polysaccharides showed weaker characteristic peaks of the sulfate position by comparing with the native samples,indicating the desulfurization method was effective to remove the sulfate content.The effect of sulfate content on the exhibition of the antioxidant and anti-tumor capacities had been evaluated and compared.The results showed that all polysaccharide fractions had certain antioxidant activities and inhibitory of the growth of DLD-1 intestinal cancer cells capacities.Specifically,UFP2 with relatively high sulfate content,molecular weight and uronic acid content had consistently excellent antioxidant performances.However,UFP2 indicated the minimal inhibitory effects on growth of DLD-1 intestinal cancer cells.Instead,DS-UFP3 with the lowest sulfate content but highest uronic acid content and molecular weight exhibited the best antitumor activity.UFP3 was purified by DEAE Sapharose Fast Flow and Sephacryl S-300 gel chromatography.One water-soluble pure polysaccharide UFP3-21 was obtained.High performance liquid chromatography producing a single symmetrical peak,indicated that UFP3-21was homogeneous and the molecular weight was 303.626 kDa.IR spectra indicated the sugar characteristic peaks were existed.Gas chromatography-mass spectrometry showed that UFP3-21 was mainly composed of rhamnose xylose and glucose and the molar ratio of 1.00:0.16:0.09?Chemical shift in NMR spectrum on 25? showed that 6-deoxy sugar exists in UPF3-21,which was consistent with the monosaccharide composition containing rhamnose.The signal in 1H NMR spectrum on 60? indicated that UPF3-21 may contains three residues.There is no resonance signal at ? 82-88 in 13C NMR spectrum,indicating that the sugar residues is pyranoid glycoside.The negative peak at 19.5 in DEPT-45 spectrum might because the C6 of rhamnose is linked with other groups and make it only two protons.