Evaluation of Antioxidant Activity of Selected Medicinal Plants Using the Briggs-Rauscher Oscillating Reaction.

The Briggs-Rauscher oscillating reaction can be used as test for antioxidant activity of pure compounds and food extracts which are consumed daily, like fruits, vegetables, juices, etc. By addition of substances with antioxidant ability to the Briggs-Rauscher reaction mixture, there is an immediate quenching of oscillations, and after a certain time the oscillations start again. The time of no oscillations or inhibition time is proportional to the amount of the antioxidant added. In this study, the Briggs-Rauscher reaction was used to determine antioxidant activity of extracts of selected medicinal plants: rosemary (Rosmarinus spp.), savory (Satureja spp.), mountain tea (Sideritis spp.) and hibiscus (Hibiscus spp.). The plant extracts were prepared by the process of maceration with water and ethanol as solvent, at room temperature. The Briggs-Rauscher reaction was performed in a stationary, constantly stirred reactor with an accurately defined concentrations of reactants at temperature of 25°C. Changes in the Briggs-Rauscher reaction mixture were followed potentiometrically with platinum and silver-silver chloride electrodes. Preliminary studies have shown that ethanolic extracts of rosemary, mountain tea and hibiscus have much less antioxidant activity than the corresponding aqueous extract, while the ethanolic extract of savory had greater antioxidant activity than aqueous extract. Aqueous extract of mountain tea showed the best ability to inhibit oscillations, i.e. the highest antioxidant activity comparing to all other samples. [ABSTRACT FROM AUTHOR]