Study On The Extraction, Purification And Pharmacological Activities Of Polysaccharides From Green Tea, Black Tea And Dark Tea

Diabetic mellitus is the third non-communicable diseases that threats to human health, and its prevalence is rising sharply. At present, death and disability of diabetic mellitus is main result by vascular complications. A large of researches showed that polysaccharides have hypoglycemic activity, immune regulation, antioxidant activity and antihypertensive effects. Tea polysaccharide is the second largest active substances in tea, and it has high antioxidant activity, hypoglycemic activity and antihypertensive effect.In this paper, water extraction, ammonium oxalate extraction and alkali extraction were used to extract tea polysaccharides from green tea, black tea and drak tea. Nine kinds of tea polysaccharides were got after removed pigment and lipid, protein, small molecules and impurities. The carbohydrate content, uronic acid content, protein content of tea polysaccharides were determined by Phenol-sulfuric acid colorimetric method, m-hydroxybiphenyl colorimetric method, Bradford method. GPC, GC and IR were used to detect the average molecular weight, monosaccharide composition and configuration of tea polysaccharides. Anticoagulant activities of these tea polysaccharides and their inhibition of alpha-glucosidase were studied. The main results were followed:1. Polysaccharides from green tea had higher carbohydrate contents, while dark tea polysaccharides had higher uronic acid contents and protein contents. Analyzed by the methods of extraction, ammonium oxalate extrated polysaccharides had higher uronic acid contents. It is showed that compositions of polysaccharides were affectted by the species of tea and uronic acid contents were mainly impacted by the methods of extraction.2. Average molecular weight of nine kinds of tea polysaccharides were measured by GPC, and we found that green tea polysaccharides had high average molecular weight, and from the analysis of extraction method, ammonium oxalate extracted tea polysaccharides had high average molecular weight So, the species of tea and the methods of extraction could influence the average molecular weight of tea polysaccharide.3. Nine kinds of tea polysaccharides were analyzed by GC, and mainly composed of rhamnose, arabinose, glucose, mannose, galactose, but the monosaccharide contents were different each other.4. Infrared spectrum analysis showed that most of tea polysaccharides were β configuration.5. Anticoagulant experiments showed that three kinds of black tea polysaccharides could prolong APTT, TT, PT significantly, and three kinds of dark tea polysaccharides could prolong APTT and TT significantly, which mean they showed anticoagulant activities by intrinsic coagulation pathway. Anticoagulant activities were positive correlated with concentration, but negative correlated with the average molecular weight, and they also related to the species of tea. What’s more, polysaccharides of black tea showed strong alpha-glucosidase inhibition.These results will provide a new approach and theoretical basis for the comprehensive development and utilization of tea, and provide technical support, scientific basis for the development of tea polysaccharide series health care products and new drugs.