Determination of Antioxidant Activity in Selected Teas Using the Briggs-Rauscher Oscillatory Reaction and DPPH Assay: A Comparative Approach

This study evaluates the antioxidant activity of aqueous and methanolic extracts of green tea, black tea, forest fruit tea, and lemon juice using the standard DPPH assay with UV/VIS spectrophotometry, and the Briggs-Rauscher (BR) oscillatory reaction as a complementary analytical approach. The DPPH assay was applied to determine radical scavenging capacity through percentage inhibition and IC50 values, while the BR method was used to assess antioxidant activity based on the inhibition time caused by sample addition to the oscillatory reaction system. The obtained results showed that methanolic extracts exhibited higher antioxidant activity than the corresponding aqueous extracts in all investigated samples. Among the tested materials by DPPH assay, green tea demonstrated the highest antioxidant capacity, followed by black tea, forest fruit tea, and lemon juice. In the BR system, the methanolic extract of green tea also produced the longest inhibition time whereas black tea, forest fruit tea, and lemon showed lower but clearly distinguishable activities. The trends observed by the BR method were consistent with those obtained by DPPH assay. Results obtained in this work, indicate that the Briggs-Rauscher reaction method provides useful information about antioxidant activity of different teas. Furthermore, it represents a valuable contribution to the development of modern analytical methodologies in food chemistry.