Inhibitory Effects by Ascorbic Acid on the Oscillations of the Briggs?Rauscher Reaction

The Briggs? Rauscher oscillating reaction (in batch mode) has been shown to be sensitive to various antioxidants, some of which cause cessation of oscillations for a period of time, before a restart occurs. The length of time before oscillations restart is related to the type of antioxidant and its concentration. Procedures have been devised to apply this method as a tool for measuring antioxidant activities of pure compounds and of extracts of natural sources. The antioxidant activity in the Briggs? Rauscher system has been generally related to the reaction of an antioxidants with hydroperoxy radicals (HOO^.) present in the oscillating system. Thereby, at low concentration (<2×10^?4 M ), ascorbic acid is known to have a little effect on the reaction. However, there is a concentration range, where a nearly linear relation is observed between ascorbic acid concentration and inhibition time. We were able to model this type of inhibition by the reducing power of ascorbic acid without invoking a reaction with HOO^..