Lipid-lowering Activity Of Polysaccharides From Large Yellow Tea In Vitro

Large Yellow Tea,also known as Old Drying Baking,is mainly produced in Huoshan County,Anhui Province.Use coarse old leaves as raw materials for tea making.It is made through the steps of finishing,rolling,stuffy yellow,drying,etc.Large Yellow Tea is the partially fermented Tea,which is rich in various active ingredients and has certain nutritional value and pharmacological activity.At present,it has been reported that Large Yellow Tea has a good lipid-lowering effect,but the material basis of its active effect is still unclear.In this study,using Large Yellow Tea powder as raw material to establish an in vitro lipid-lowering model.Firstly,the lipid-lowering activity of different solvent extracts of Large Yellow Tea was screened.Then,the lipid-lowering activity of different types of active ingredients in the most active extracts was screened.Finally,we further screened out the key components of this type of active substances that have the activity of reducing lipids.The main research contents and results are as follows:(1)Research on lipid-lowering activity of different extracts of Large Yellow Tea:First,the LWE,LWEP,and LEE precipitation of Large Yellow Tea were made by hot water extraction,water extraction and alcohol precipitation,ethanol extraction.Then,the functional components:tea polysaccharides,tea polyphenols,tea proteins,and free amino acids were measured and compared,Measured and compared the lipid-lowering activity in vitro.The results indicated that compared with the other two components,the contents of carbohydrate and protein in the water extract-alcohol precipitation of Large Yellow Tea were the most abundant,and the best inhibitory activity against pancreatic lipase.Moreover,the lipid deposition in 3T3-L1preadipocytes induced by"Cocktail"method was significantly improved,and the content of lipid droplets was the least in cells.(2)Study on lipid-lowering activities of different active substances in Large Yellow Tea:According to the above conclusion,the in vitro lipid-lowering activities of tea polysaccharides and proteins in Large Yellow Tea were compared.On the one hand,The results showed when the amount of polysaccharide equals the amount of protein,the lipase inhibition activity of tea polysaccharide group was significantly better than that of protein group,and the amount of lipid accumulation n in 3T3-L1 preadipocytes after differentiation was also less than the protein group.On the other hand,with the increase of polysaccharide content,the inhibition effect of the Large Yellow Tea polysaccharide on pancreatic lipase and the amelioration of lipid deposition in 3T3-L1 cells was the better.(3)Study on lipid-lowering activity of polysaccharides from the Large Yellow Tea:On the basis of the above studies,Tea polysaccharides from Large Yellow Tea with different molecular weight range were prepared by polyamide chromatography deproteinization and decolorization and ultrafiltration membrane separation technology:below 1×10~4 Da(LYTP-1),1×10~4-1×10~5Da(LYTP-2),1×10~5-5×10~5 Da(LYTP-3),and above 5×10~5Da(LYTP-4).Their physicochemical properties,the improvement of pancreatic lipase inhibitory activity,and lipid accumulation induced by oleic acid(OA)in Hep G2 cells were measured and compared.The results indicated that the inhibitory effect of LYTP-2 on pancreatic lipase and the improvement of lipid accumulation in OA-induced Hep G2 cells were better than those of other groups of tea polysaccharides.The basic physical and chemical properties was analyzed results showed that Large Yellow Tea polysaccharide LYTP-2 in the neutral sugar content was 23.72±1.86%,uronic acid content was 63.11±4.26%,protein content was 6.86±1.14%,including uronic acid content is higher than other groups of polysaccharide,The infrared absorption spectrum analysis it conformed to the infrared absorption characteristics of polysaccharide,The monosaccharide composition analysis results showed that LYTP-2 was mainly composed of D-galacturonic acid,D-arabinose,D-galactose,L-rhamnose,D-glucose,D-mannose,D-Glucuronic acid,and their molar ratio was 11.51:1.73:1.68:1.62:1.00:0.22:0.17.The scanning electron microscopy(SEM)showed that the surface of LYTP-2 was irregular flakes and spherical,the surface has small holes of different sizes,.The Congo red experiment showed that the surface of LYTP-2 had a triple helix structure.At the same time,The cell experiments showed that the intervention of the Large Yellow Tea polysaccharide LYTP-2 could significantly reduce the production of reactive oxygen species(ROS)in Hep G2 cells induced by OA,and also improve the apoptosis phenomenon of Hep G2 cells induced by OA,and these effects were better than other components.In addition,the cytotoxicity test results showed that LYTP-2 had not adverse effects on normal liver cell LO2.In conclusion,tea polysaccharides with molecular weight range of 1×10~4-1×10~5 Da are the active substances for lowering lipid effect in Large Yellow Tea,and they have no cytotoxicity to normal liver cells LO2.