Structural Characterization And Anti-inflammatory Activity Of Polysaccharides From Houttuynia Cordata

Houttuynia cordata,a medicinal and food homologous plant,belongs to the Saururus chinensis family with antibacterial,cough relieving and anti-inflammatory effects,which are closely related to its polysaccharide composition.In this research,various chemical analysis methods（acid hydrolysis,carbonyl reduction,methylation reaction）and instrumental analysis technology（UV,FT-IR,HPGPC,GC,GC-MS,NMR）were applied to characterize the structure of polysaccharides from Houttuynia cordata.Meanwhile,the anti-inflammatory activity of polysaccharide from Houttuynia cordata was analyzed in vitro experiments.The main results of the research were as follows:Four polysaccharide fractions（HBHP,CHHP,DAHP and CAHP）from Houttuynia cordata were obtained by extracting sequentially with hot water,0.05 mol/L EDTA-2Na solution,0.2 mol/L alkali solution and 1 mol/L alkali solution.Chemical composition demonstrated the sugar content of the four fractions were 66.4%,63.2%,60.6%,and 62.8%,and the uronic acid content was 29.6%,22.6%,18.5%,11.6%,respectively.HBHP and CHHP were composed of rhamnose,arabinose,glucose and galactose with molar ratios of9.7:11.9:10.6:21.4 and 11.3:17.8:7.6:18.9 respectively.DAHP and CAHP consisted of arabinose,xylose,glucose and galactose with molar ratios of 14.1:17.0:9.0:13.8 and 6.6:37.5:9.9:6.3,respectively.The results of scanning electron microscopy showed that HBHP,CHHP,and DAHP had a larger specific surface area.And thermogravimetric analysis suggested CAHP had the best thermal stability.Two homogeneous polysaccharides（HBHP-3 and HBHP-4）were obtained from HBHP by DEAE Cellulose-52 with molecular weights of 397.4 k Da and 616.7 k Da,and uronic acid content of 20.9%and 14.8%,respectively.The results of monosaccharide composition showed the molar ratios of rhamnose,arabinose,glucose,galactose and galacturonic acid in HBHP-3 and HBHP-4 were 16.0:12.6:4.6:18.1:15.6 and 34.1:6.9:5.0:16.2:10.0,respectively.Structural analysis manifested that the backbone of HBHP-3 consisted of→2)-α-D-Rhap-（1→,→4）-α-D-Galp A-（1→and→4）-β-D-Galp-(1→with the branched chainsα-L-Araf-（1→,→5）-α-L-Araf-（1→,→4）-α-D-Glcp-（1→,→6）-β-D-Galp-(1→andβ-D-Galp-（1→substituted at O-4 osition of→2）-α-D-Rhap-（1→.The main chain of HBHP-4 consisted of→2）-α-D-Rhap-（1→,→4）-α-D-Galp A-（1→and→4）-β-D-Galp-(1→with the branched chainsα-L-Araf-（1→,→4）-α-D-Glcp-(1→andβ-D-Galp-（1→substituted at O-4 osition of→2）-α-D-Rhap-(1→.Antioxidant tests exhibited Houttuynia cordata polysaccharides had better antioxidant activity within the measured concentration range,among which HBHP had outstanding hydroxyl radical and DPPH radical scavenging activity,while DAHP had the highest ABTS radical scavenging activity and Fe²⁺chelating ability.As for immunomodulatory activity,the four fractions all had good immunomodulatory activity,which was positively correlated with the concentration of polysaccharides.Among them,HBHP exhibited the significant activation effect on macrophages,which obviously improved the phagocytic ability of macrophages.The results of anti-inflammatory tests showed HBHP-3 and HBHP-4 had a significant inhibitory effect on the inflammatory response of macrophages induced by LPS in the concentration range of 5 to 100μg/m L.HBHP-3 and HBHP-4 not only inhibited the secretion of NO by macrophages in a dose-dependent manner,but also distinctively reduced the m RNA level of pro-inflammatory cytokines.Western-blot analysis suggested that HBHP-3 exerted an anti-inflammatory effect by inhibiting the phosphorylation levels of NF-κB protein（p65）and IκBαinduced by LPS.