| Undaria pinnatifida,which is mainly distributed in Liaoning,Shandong and Zhejiang province in China,is a kind of edible seaweed belongs to Phaeophyta.In addition to natural reproduction,there has been artificial breeding of Undaria pinnatifida in the northern coastal areas,Undaria pinnatifida has become the third largest cultivated seaweed in China.Studies have shown that polysaccharides from Undaria pinnatifida possess many biological activities such as anti-tumor,anti-virus,immunomodulatory,and so on.In this study,the chemical composition,structural characteristics and immunomodulatory activities of polysaccharides from Undaria pinnatifida were studied.The main results obtained are as follows:(1)Undaria pinnatifida polysaccharide(UPP)was obtained by traditional water extraction with a yield of 11.00 ± 0.25%.The molecular weight of UPP was 691.05 kDa,and the contents of carbonhydrate,uronic acid,sulfate and protein were 50.02 ± 1.14%,14.98 ± 0.52%,11.19 ± 0.40% and 2.37 ± 0.17%,respectively.UPP was composed of glucose,xylose,mannose,arabinose,fucose,galactose and rhamnose,while glucose and xylose contributed to a total molar percentage of 71.39%.UPP consisted of(1?2)or(1?4)glycosidic bond by 62.36% as well as(1?3)glycosidic bond by 35.78%.(2)UPP was fractionated by DEAE Sephrose fast flow chromatography and four fractions named UPP-1,UPP-2,UPP-3,UPP-4 were obtained.Among them,UPP-2 and UPP-3 were relatively abundant.The carbonhydrate content of the obtained fractions was 66.69%-79.93%.UPP-2,UPP-3 and UPP-4 were found to contain much uronic acid and sulfate.Besides,both UPP-2 and UPP-3 contained a small amount of protein(< 1.50%).(3)Oxygen radical absorbance capacity(ORAC),ABTS scavenging capacity and DPPH scavenging capacity assays were applied to evaluate the antioxidant activities of Undaria pinnatifida polysaccharides(UPPs).Results showed that oxygen radical absorbance capacity of UPPs ranked as follows: UPP > UPP-4 ? UPP-3 > UPP-2 > UPP-1,and ABTS scavenging capacity of UPPs ranked as follows: UPP > UPP-4 > UPP-3 ? UPP-2 > UPP-1,while DPPH scavenging capacity of UPPs were weak.Data showed that the ABTS scavenging capacity values of the four fractions were 18.67-41.07 ?mol Trolox/g,while DPPH scavenging capacity values were 8.40-26.54 ?mol Trolox/g.(4)UPP-2 and UPP-3 were filtered out as immune-active polysaccharides mainly based on the NO release results,and their immunomodulatory activities were evaluated at gene regulation and protein expression levels,respectively.RT-QPCR experiments showed that both UPP-2 and UPP-3 could significantly increase the mRNA expression of iNOS,TNF-?,IL-6 and IL-1? in RAW264.7 cells.The release of TNF-? in RAW264.7 cells treated with different concentrations of UPP-2 and UPP-3 were 39-74 and 31-68 times to those of normal cells,respectively,while the IL-6 release was 3-189 and 2-86 times to those of normal cells,respectively,which coincided with the expression of corresponding mRNA approximately.However,UPP-2 and UPP-3 had little effect on the release of IL-1?.Comprehensive view that UPP-2 and UPP-3 possess significant immunomodulatory activities.(5)The monosaccharide composition analysis demonstrated that UPP-1 mainly consisted of mannose,xylose and fucose with molar percentages of 66.73%,12.04% and 8.49%,respectively.UPP-2 was mainly composed of xylose(64.55%)and glucose(23.81%),and UPP-3 also mainly consisted of xylose and glucose with molar percentages of 34.59% and 41.73%,respectively.According to the periodate oxidation and Smith degradation analysis,UPP-2 mainly consisted of(1?2)or(1?4)glycosidic bond(90.10%),while UPP-3 consisted of(1?2)or(1?4)glycosidic bond by 57.54% as well as(1?3)glycosidic bond by 41.58%.There was little(1?)or(1?6)glycosidic bond in UPP-2 and UPP-3.(6)The methylation and NMR analysis demonstrated that UPP-2 were mainly linked with ?2)-?-D-Xylp-(1?,?4)-?-D-Glcp-(1?,?-D-Xylp-(1? and ?2,4)-?-D-Xylp-(1? with a bit of ?4)-?-D-Xylp-(1?,?5)-?-L-Araf-(1? and ?4)-?-D-ManpNAc-(1?.The branching ratio of UPP-2 was calculated to be 16.37%.UPP-3 were mainly linked with ?2,3,4)-?-DXylp-(1?,?2,4)-?-D-Glcp-(1? and ?4,6)-?-D-Glcp-(1? with a bit of ?4)-?-L-Rhap-(1?,?6)-?-D-Galp-(1?,?-D-Glcp-(1?,?3)-?-D-ManpNAc-(1? and ?3,4)-?-D-GlcpNAc-(1?.Results showed that UPP-3 was a highly branched polysaccharide with a significantly higher branch ratio compared with UPP-2. |
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