Suppression of free-radicals and protection against H2O2-induced oxidative damage in HPF-1 cell by oxidized phenolic compounds present in black tea

Whereas catechins are the most abundant polyphenols in green tea, the typical pigments in black tea are theaflavins (TF), thearubigins (TR) and theabrownins (TB), which are derived from the oxidation of catechins and their gallates during the fermentation stage of black tea processing. In this study, oxidized phenolic compounds (TF, TR and TB) present in black tea were obtained from a model oxidation system, using immobile enzyme. The order of OH− and 2,2-diphenyl-1-picrylhydrazyl-scavenging ability of these oxidation products was TF > TB > TR. These oxidized phenolic compounds showed protection against H2O2-induced damage in HPF-1 cells and suppressed the accumulation of intracellular reactive oxygen species in H2O2-induced damage of HPF-1 cells. Interestingly, TB, as a further oxidative product from TF or TR, showed potent activity, followed TF in the above four systems.