Antioxidant activity of melanins derived from tea: comparison between different oxidative states

The antioxidant activity of tea melanin (TM) derived from tea leaves was studied. The influence of TM on the kinetics of the free-radical oxidation of β-carotene revealed essential differences between their oxidative states. The reduced preparation of TM delays the oxidation of β-carotene. The lag time increased in proportion to concentration of TM. The oxidized preparation of TM decreases the rate of β-carotene consumption, but does not affect the lag time. The kinetic characteristics of the antioxidant activity of TM can be explained by the participation of phenol and quinone groups in free-radical chain reactions. Antioxidant properties of TM can be utilized for prevention of free-radical oxidation of natural products.