Extraction,Purification,Structural Modification And Hepatoprotective Activity Of Pectin Polysaccharide From Fresh Dendrobium

The application of Dendrobium has been paid attention to "fresh products first".Modern research shows that the content of polysaccharides,alkaloids and other active components in fresh Dendrobium is higher than that in dry Dendrobium,but the research on polysaccharides and their liver protection activities in fresh Dendrobium is still scarce.In this study,we speculated the main structural characteristics of pectin's hepatoprotective activity through the difference of its hepatoprotective activity between fresh and dry Dendrobium.Then,on the basis of the structure analysis and hepatoprotective activity data of the modified pectin obtained by ultrasonic and enzymatic methods,we preliminarily discussed the structure-activity relationship between pectin's structure and hepatoprotective activity by principal component analysis and multiple linear regression analysis,so as to provide reference for fresh Dendrobium It can provide a reference for the development.The main results are as follows(1)The protective effect of fresh Dendrobium pectin polysaccharide on acute alcoholic liver injury(ALD)mice was better than that of dry Dendrobium.Fresh and dried Dendrobium pectin were extracted by acid water at p H 1.5,deproteinized,decolorized and purified,then eluted with 0.3 M Na Cl to obtain uniform pectin polysaccharides(FDP and DDP).The acute toxicity test in mice showed that FDP and DDP were low toxic substances(LD50 > 2 g / kg b.w.).ALD mouse model was established by intragastric administration of 50% ethanol.The liver protective activity was evaluated by serum transaminase index,liver antioxidant enzyme,alcohol metabolic enzyme index and inflammatory factor index after intragastric administration of FDP and DDP(100,200 and 300 mg / kg)for three weeks.The results showed that FDP and DDP could increase liver antioxidant enzyme and alcohol metabolic enzyme index,and reduce transaminase activity and inflammatory factor index.Besides,FDP was superior to DDP in transaminase,liver antioxidant and inflammatory factors.(2)The degree of acetylation(DAc),molecular weight,mannose / glucose,rhamnose and branched chain of Dendrobium polysaccharides may be the main structural factors that cause the difference of liver protective activity between FDP and DDP.The results of structural analysis of FDP and DDP showed that the DAc of FDP was16.4,the molecular weight of FDP was 14.8 k Da,and FDP was mainly composed of glucuronic acid,galacturonic acid,galactose,glucose,mannose and a small amount of rhamnose and xylose.It contained HG,RG-I and XGA polysaccharides.The glycosidic bonds were mainly 1,4-linked-Glcp,1,4-linked-Galap,1,6-linked-Galp and 1,6-linkedManp.The DAc of DDP is 12.7,and the molecular weight of DDP is concentrated in 10.7k Da and 1.5 k Da.The monosaccharide composition of DDP is slightly different from that of FDP,which is mainly reflected in the loss of rhamnose and the decrease of mannose content.DDP contains HG and XGA type polysaccharides,and the glycosidic bonds are mainly 1,4-linked-Glcp,1,3,4-linked-Glcp,1,4-linked-Galap and T-linked-Galp.(3)The DAc,molecular weight,monosaccharide content and branched chain degree of pectin were changed by ultrasonic and pectinase modification,but the liver protection activity was slightly decreased.Ultrasonic(100,200,300,400 W)and pectinase(0.025,0.050,0.075,0.100 g / L)were used to treat FDP to obtain ultrasonic modified pectin(U1,U2,U3,U4)and enzyme modified pectin(E1,E2,E3,E4).The chemical structure analysis showed that the basic configuration and monosaccharide species of modified pectin were basically unchanged.The content of acetylation degree,molecular weight,galactose,rhamnose and mannose decreased,and the proportion of galacturonic acid,glucose,glucuronic acid,xylose and branched chain degree increased.The order of hepatoprotective activity evaluated by liver index,ALT and AST was FDP > U1 > E1 > DDP > U2 > E2 > U3 > E3 > U4 > E4.(4)The DAc,branched chain degree and molecular weight of Dendrobium pectin were the key structural characteristics affecting the hepatoprotective activity of Dendrobium pectin.Based on the data of DAc,molecular weight,glucuronic acid,rhamnose,xylose,mannose / glucose,branched chain structure of FDP,DDP,ultrasonic and pectinase modified pectins(U1,U2,U3,U4 and E1,E2,E3,E4),as well as transaminase,liver antioxidant,alcohol metabolism and anti-inflammatory factors in serum,principal component analysis and multiple linear regression were used.The results showed that DAc,branched chain degree and molecular weight were the key structures affecting the hepatoprotective activity of Dendrobium pectin.