Abstract:

Polysaccharides were extracted from different teas with hot water and their contents were determined by sulfuric acid-phenol method, while polyphenols were extracted with alcohol and their contents were determined by ferrous tartrate method. Then the scavenging effects of tea polysaccharide and polyphenol on free radicals were examined by DPPH·, salicylic acid and pyrogallol methods respectively, and the antioxidant capabilities of 8 kinds of tea were comparatively studied. Results showed that the polysaccharides contents in different teas are from 2.19% up to 2.89% and their change order is as following: semifermented oolong tea ＞ black tea ＞ green tea. The polyphenol contents in different teas are from 1.71% up to 9.75% and their change order is as following: green tea ＞ semifermented oolong tea ＞ black tea. The order of antioxidant capability is black tea ＞ green tea ＞ semifermented oolong tea (DPPH· and salicylic acid methods) or black tea ＞ semifermented oolong tea ＞ green tea (pyrogallol method). Both tea polysaccharides and polyphenols are main antioxidants in different kinds of teas. The antioxidant capability of green tea mainly depends on polyphenols, while that of black tea mainly depends on polysaccharides. Furthermore, the antioxidant capabilities of both polysaccharides and polyphenols are proportional to their contents in various tea extracts except aqueous polysaccharide extract of oolong tea.

Key words: tea, polysaccharide, polyphenol, free radical scavenging rate, DPPH·, method, salicylic acid method, pyrogallol method