| Root of Saposhnikovia divaricate(Turcz.)Schischk(SD),a traditional Chinese herbal medicine called "Fangfeng",is commonly used to treat rheumatism,arthralgia,headaches,stroke,fever,cold,etc.Schloars have focused on the structure and activity researches of small molecular substances extracted from SD,such as chromones and coumarins et al.However,the SD polysaccharides(SDP)extracted from the traditional decoction achieved few attention.Existing studies show that the SDP possess the effects of immuno-regulation,anti-oxidant and anti-tumor activity in vivo.Whereas,the ambiguously structure analysis limited our overall understanding of the structure-activity relationship of SDP.According to systematic extraction and separation,we successfully achieved four fractions from Saposhnikovia divaricate(SD)and named SDP1?SDP4,respectively.Their molecular weight,monosaccharide compositions,linkage modes and structural properties were characterized with SEC-MALLS,HPAEC-PAD,GC-MS and NMR.SDP1 was assigned as a a-1,4-glucan with small amount of O-3/6 linked branches.SDP2 mainly contained a-1,4-glucan and a little arabinogalactan,whereas SDP3 is mainly composed of arabinogalactan with a small amount of a-1,4-glucan.SDP4 was defined as a pectic arabinogalactan.Four fractions showed antioxidant activities in both molecular and cellular levels.The ABTS scavenging rates were plotted as a function of the concentrations of SDPs.All these four fractions showed concentration-dependent scavenging activity against ABTS radicals and their antioxidant activity was ranked as SDP4?SDP3>SDP2>SDP1.Furthermore,pre-incubation of RAW264.7 cells with SDPs at concentration from 1 to 100 ?g/mL prior to H2O2 treatment could protect the cells from oxidant injury and show the protective activity trends in which the protective effect from top to down was SDP4>SDP3>SDP2>SDP1.ROS kit revealed the effect of SDPs which could significantly reduce the intracellular ROS of RAW264.7 cells at the concentration of 100 ?g/mL.Finally,the influence of SDPs on the phagocytic activity of RAW264.7 cells was preliminarily analyzed by neutral red.Contrasted by the blank group,SDP2?4 could strengthen the phagocytic activity of RAW264.7 and show dose dependent activity which the phagocytic activity from top to down was SDP4>SDP3>SDP2.Preliminary pharmacological studies in vitro revealed that the antioxidant activity of SDP containing arabinogalactan was significantly higher than that containing fewer arabinogalactan.In addition,the antioxidant activity of SDP without arabinogalcan was relatively weak.The pectic arabinogalactan in SDP4,which was the main component existed in SDP,was further analyzed by 1D/2D NMR and HPAEC-PAD-Q/TOF-MS.Compared by the NMR analysis of SDP4 and SDP4 enzymed by endo-1,5-?-L-Arabinanase,SDP4 was mainly composed of ?-1 4-Galctan,?-1,5-Arabinan which existed branches at O-3 and?-1,4-Galacturonan with the degree of esterification of 24%.Monosaccharides and dissacchairdes of ?-1,4-Gal combined with oligosaccharides of Ga1A from dp1 to dp6 were existed in the SDP4 enzymed by endo-1,4-?-Galactanase,which means the unbranched homogeneous ?-1,4-galacturonan in SDP4 was connected to the backbone of SDP4.The detected ?-1,4-galacturonan was also observed in NMR spectrums which comfirmed the result of SDP4 analysis.The overall results showed that SDP4 was a typical pectic arabinogalactan.These results would provide comprehensive information about the carbohydrate structure and the antioxidant bioactivity of SDPs.Simultaneously,the glycosidic linkage of SDP4 which was the main antioxidant component in SDPs was further elucidated according to enzymatic method.As a tradinational Chinese medicine,SD has a long history to treat different sickness.However,the details of structure and activity of SDPs were still lacking which need our further endeavor to discover the new carbohydrate and activity of SDP. |
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