Behavior of phenolic antioxidants in a partitioned medium: Focus on linoleic acid peroxidation induced by iron/ascorbic acid system

The peroxidation of linoleic acid was induced by the Fe2+/ascorbic acid system in a micellar medium, and the kinetics of the produced conjugated dienes were followed. The ascorbic acid concentration was adjusted to a weak level (0.7 mu M) in order to initiate only the sequential oxidative reactions without superimposed antioxidant activity. Other conditions were established to obtain a simple kinetic profile. With a linoleic acid/Fe2+ ratio of 10 and an Fe2+/ascorbic acid ratio of 23 in the medium emulsified by Tween and saturated in oxygen, no limiting effect of;substrates was observed for several hours. Fe2+ disappeared in less than 5 min, while a linear propagation rate was reached after 1 h for up to 15 h. Two parameters were chosen to quantify the level of the oxidation: the slope of the linear phase, and the extrapolated absorbance of this step at zero time. These two parameters were used in order to compare the antioxidant power of different phenolic compounds in this partitioned medium.