Measurements of the antioxidant capacity of fruits and vegetables using the BR reaction method

The antioxidant capacity of aqueous extracts of 20 vegetables and 16 fruits have been determined using the Briggs-Rauscher (BR) reaction method. Like other methods, the BR reaction method is also based on the generation of free radicals in the reaction mixture. Antioxidant scavengers of free radicals added to an active oscillatory BR regime cause an immediate cessation of the oscillatory regime, an inhibition time that linearly depends on the amount of the antioxidant added, and subsequent regeneration of oscillations. The BR reaction method works at pH approximate to 2, which is similar to that of the fluids in the human stomach. It is known that a vegetarian diet can reduce the risk of stomach cancer and it is therefore interesting to determine the activity of antioxidants at low pH values. Different plants were tested with the BR reaction method, recording potentiometrically the inhibition times produced by their extracts on an active BR mixture. The results concerning the order of the antioxidant activity of the examined plants are illustrated and discussed. A comparison with the ranking order obtained with other methods is also given.