Extraction,Purification,Structural Characterization And Anti-tumor Activity In Vitro Of Polysaccharides From Dark Tea

Dark tea has unique organoleptic properties and health benefits such as antioxidant,fat-reducing,and anti-tumor.Recently,more and more attention has been paid to tea polysaccharides due to their diverse activities and applications.In this study,Fuzhuan dark tea with regional characteristics was taken as the research object,and the basic physical and chemical properties,structural characteristics and in vitro anti-tumor activity of water-soluble dark tea polysaccharides were thoroughly studied.This has accumulated a solid experimental foundation for in-depth exploration of the structure and activity of dark tea polysaccharides.The main findings are as follows:（1）The crude polysaccharide was obtained by water extraction,alcohol precipitation,deproteinization and dialysis from Fuzhuan dark tea with a yield of 3.7%.Then two water-soluble dark tea polysaccharides DTP-1 and DTP-2 were obtained by combining cellulose column and Sephadex column for purification.（2）The particle size distribution and conformational morphology characteristics of DTP-1 and DTP-2 were observed by chemical analysis and instrumental analysis.DTP-1 and DTP-2 are similar.The size of those particles was mostly concentrated in the range of 100-200 nm.Then the particle behaviors of the two were similar,they both had aggregation behavior in water,existed as irregular sheet-like structures with rough surfaces,and did not have triple helix structure.（3）The results of gel permeation chromatography and ion chromatography showed that the Mw of DTP-1 was 11805 Da and the Mw of DTP-2 was 20898 Da,and both of them were acidic homogeneous polysaccharides.In addition,DTP-1 and DTP-2 contained the same monosaccharide composition,including glucose,galactose,arabinose,rhamnose,and galacturonic acid,with slightly different proportions.The basic structural units of DTP-1 and DTP-2 were rationally deduced from the results of methylation and nuclear magnetic resonance.The basic structural framework of DTP-1 was→[2)-α-L-Araf-（1→5）-α-L-Araf-（1]₂→2）-α-L-Araf-（1→6）-β-D-Galp-（1→2）-α-L-Araf-（1→4,6）-β-D-Galp-（1→4）-α-D-Glcp-（1→3）-β-D-Galp-（1→[4）-α-D-Glcp-(1]₅→,and the branch wasβ-D-Glcp-（1→.And the basic framework of DTP-2 was→4）-β-D-Galp-（1→4,6）-β-D-Galp-（1→5）-α-L-Araf-（1→3）-β-D-Galp-（1→[4）-α-D-Glcp-(1]₄→,and the branch wasα-L-Araf-(1→.（4）The anti-tumor activity in vitro of DTP-1 and DTP-2 was explored by establishing cells model.The experimental results showed that both DTP-1 and DTP-2 could effectively inhibit the growth of cancer cells（A549 cells and 7721 cells）,induce their apoptosis and slow down their migration.The highest proliferation inhibition rate was 41.4%（600μg/m L,24 h）.In addition,DTP-1 and DTP-2 did not adversely affect the corresponding normal cells.This study provides scientific ideas and methods for the comprehensive development and utilization of dark tea,and provides the material and theoretical basis for the development of dark tea polysaccharides as functional foods and drugs for adjuvant treatment of cancer.