Comparative study on anti-oxidant capacity of extracts prepared from differently-fermented tea and the cellular antioxidant activity assay of tea polyphenol

The in vitro antioxidant activities of tea extracts prepared from differently-fermented tea were evaluated and compared by 2,2-diphenyl-1-picrylhydrazyl(DPPH) radical scavenging activity assay and oxygen radical absorbance capacity(ORAC) assay, and the correlation between antioxidant activities and functional components of tea extracts were analysized in order to define the main antioxidant substance. Meanwhile, the cellular antioxidant ability of major antioxidant substance in the extracts was measured by cellular antioxidant activity(CAA) assay with human hepatoma cells HepG2. The results showed that the antioxidant activity of tea extracts is dependent on the fermentation degree of tea ranked as the following:non-fermented teasemi-fermented teafull-fermented teapost-fermented tea. Correlation analysis showed that the content of tea polyphenols had high significant positive correlation with antioxidant activity(P0.01), amino acid content also had influence on the antioxidant capacity of tea extract(P0.05) to a certain degree. CAA value of tea polyphenols was corresponding to 44.2±1.24 μmol Quercetin/100 μmol, indicating that tea polyphenols exhibit high cellular antioxidant activity.