Food-derived antioxidants. Evaluating their importance in food and in vivo

Antioxidants in food are of interest for four major reasons: they can protect the food itself against oxidative damage, they can exert antioxidant effects in the human gastrointestinal tract, they can be absorbed and exert antioxidant effects in other body tissues, and they may be used in plant extracts, or as pure compounds, as therapeutic agents. Evaluation of each of these functions requires methods for characterization of antioxidant activity in vitro, as well as techniques that accurately measure oxidative damage in the human body and can be used to evaluate the effects of antioxidants in vivo. This article critically reviews the techniques that are currently available for in vitro and in vivo antioxidant characterization.