| Ya ’an Tibetan tea is a kind of post-fermented black tea with unique technology.It is the ancestor of Chinese black tea and has a long history and culture.In recent years,tea polysaccharides have attracted much attention due to their outstanding biological activities,including antioxidant,hypoglycemic,regulation of intestinal microorganisms and other functions.However,at present,the basic theories of Ya ’an Tibetan tea have not been studied deeply enough,and the microbial characteristics of polysaccharide digestion,absorption and colysis of Tibetan tea are relatively few,which limits the development of Tibetan tea to a certain extent.Therefore,this study takes Tibetan tea as the research object,and uses hot water extraction method(90℃,4 h)to extract polysaccharides from four kinds of Tibetan tea(Fuding,Meizhan,Sichuan tea,131),to explore the changes of chemical indexes,structure,antioxidant and hypoglycemic activity of the polysaccharides of four kinds of Tibetan tea by simulated digestion and colysis in vitro.And the changes of p H and shortchain fatty acid(SCFAs)in the products of colysis,and the community structure of the microorganism was analyzed by high-throughput sequencing.The main results are as follows:The results show that the main chemical components of the four polysaccharides are carbohydrates,uronic acid,and contain a small number of proteins and polyphenols.The main monosaccharides were rhamnose(Rha),galacturonic acid(Gal A),galactose(Gal)and arabinose(Ara).The molecular weights of the four polysaccharides were 116,777 Da,95994 Da,72685 Da and 97216 Da.In addition,after the simulated digestion of the four polysaccharides,the total sugar,reducing sugar,protein and polyphenols did not show significant changes,and the molecular weight and monosaccharide composition changed slightly.This revealed that the main structure of polysaccharides could not be degraded in the gastrointestinal tract,but could enter the large intestine relatively intact and be used by intestinal microorganisms.CTPS(67 mg VcE/g,77 mg VcE/g)and YTPS(62 mg VcE/g,74 mg VcE/g)showed better antioxidant and hypoglycemic activities.In addition,in the hypoglycemic activity,MTPS(236 mg Acarbose E/g,295 mg Acarbose E/g)and CTPS(238 mg Acarbose E/g,273 mg Acarbose E/g)showed better activity.After simulated digestion,the antioxidant and hypoglycemic activities of the four polysaccharides were slightly lower than those before digestion,but still showed good activity.The two kinds of activities of the four kinds of polysaccharides were significantly reduced after fermentation,which also indicated that the fermentation of intestinal microorganisms greatly affected the functional activities of polysaccharides.After 24 h simulated fermentation in vitro,the microorganisms could use Tibetan tea polysaccharide well to reduce the p H value in the fermentation liquid and produce a large amount of acetic acid,propionic acid and n-butyric acid.In addition,the relative abundance of Prevotella and Bifidobacterium of MTPS,CTPS,YTPS and FTPS increased significantly,while the proportion between Firmicutes and Bacteroidetes decreased significantly.Linear discriminant analysis also found that Prevotella,a healthy bacterium in MTPS group,was the dominant species,which also suggested that polysaccharide had potential probiotic activity.Correlation data showed that Bifidobacterium was significantly positively correlated with total SCFAs,acetic acid,propionic acid and n-butyric acid production.In conclusion,Tibetan tea polysaccharides(MTPS,CTPS,YTPS and FTPS)can be used as potential microbial regulatory products to improve intestinal microflora and benefit human health.Meanwhile,the experimental results also provide a theoretical basis for the development of Tibetan tea. |
PDF Full Text Request