Abstract:

The synergistic antioxidant activity of tea polyphenols with nuciferine in vitro was evaluated by determining their
abilities to scavenge DPPH and ABTS free radicals and protect against Cu2＋/H2O2-induced protein damage. Cytotoxicity of
tea polyphenols on Caco-2 cells was assessed by MTT, AO/EB and DAPI assays. The results showed that tea polyphenols
and nuciferine could significantly scavenge DPPH and ABTS free radicals, and significantly protect against Cu2＋/H2O2-
induced protein damage in a dose-dependent manner with an obvious synergism between both antioxidants. Tea polyphenols,
when used at a concentration of 1 mg/mL, significantly reduced the viability of Caco-2 cells after 24 h incubation. In
conclusion, tea polyphenols and nuciferine scavenge DPPH and ABTS free radicals and protect against oxidative protein
damage in a synergistic way. Tea polyphenols significantly reduce the viability of Caco-2 cells.

Key words: tea polyphenols, nuciferine, antioxidant activity, synergistic effect, Caco-2 cell, apoptosis