Composition and antioxidant activity of polysaccharides of different dark tea

The polysaccharides from dark tea of Fuzhuan tea, Qingzhuan tea, Liubao tea, Kangzhuan tea, Pu-erh tea, and Qianliang tea were prepared after extraction with hot water, precipitation with ethanol and deproteinization with sevage regent.Then, the neutral sugar, uronic acid, protein and polyphenol contents of six kinds of dark tea polysaccharides were measured using chemical methods.Finally, their antioxidant activities were evaluated using the ABTS assay, DPPH assay, FRAP assay and total reducing power assay.The results showed that there were some differences of chemical composition and antioxidant activity between six kinds of dark tea polysaccharides, and the contents of neutral sugar, protein, uronic acid and tea polyphenol of dark tea polysaccharides respectively were in ranges from 502.49 to 632.87 mg/g, 45.45 to 104.84 mg/g, 183.44 to 229.16 mg/g, 14.94 to 100.83 mg/g, and Pu-erh tea polysaccharide contained the highest carbohydrate, protein and polyphenol contents while Qianliang tea polysaccharide contained the highest uronic acid content, and the order of their antioxidant capacity from high to low was Pu-erh tea, Kangzhuan tea, Liubao tea, Qingzhuan tea, Fuzhuan tea and Qianliang tea in all the four evaluation system.The results provided the basis for further research on composition and antioxidant activity of dark tea polysaccharides as well as their functional product development.