How to understand the dichotomy of antioxidants.

One of the most bewildering aspects of antioxidants is that their excellent in vitro activity cannot necessarily be translated into in vivo effect. Through summarizing the recent progresses made in free radical chemistry and biology, this dichotomy is tentatively explained in terms of the heterogeneity of biological systems and the interactions between antioxidants and surrounding molecules in vivo, which also has important implications for updating the current strategies for screening and designing antioxidant drugs.