Abstract: To explore antioxidation capability and the extraction mechanism of the separation-purification of flavonoids from tea in aqueous two-phase systems, flavonoids from tea was taken as an index, to optimize the conditions for the extraction of flavonoids from tea, the effect of each factor such as weight and amounts of PEG, kinds and amounts of salt, temperature, pH have been studied by single factor and response surface methodology. Based on the single factor experiments, a three-factor (the amount of Na₂SO₄, PEG600, MgCl₂) and three-level experiment design has been developed by Box-Behnken central composite design method. The antioxidant activity of different concentration flavonoids were assessed through reducing power assay, Scavenging effects on DPPH radicals and results were compared to reference antioxidant BHT and Vc. The result showed that the optimum conditions as follows, pH 5, the extracting temperature 30℃, the amount of 5mL Na₂SO₄ 15%, the amount of 6g PEG600, the amount of MgCl₂ 2.9%, the extraction field 96.31%. The two aqueous phase system for flavonoid extraction is easy to get good reproductivity, and applied in mass production. The flavonoids from tea showed strong antioxidant activity. The flavonoids from tea are a potential product of natural safe and effective antioxidant.

Key words: tea, flavonoid, aqueous two-phase system, response surface analysis, anti-oxidation