A handy-assay procedure to measure simultaneously the polyphenol content and the antioxidant capacity in teas using the Folin Ciocalteu reagent

Resumo

Folin Ciocalteu reagent (FCR) is commonly used for the quantification of total polyphenol content (TPC) in plants and theirs derived materials. Tea is one of the most consumed beverages in the world and widely used in developing countries in folk medicine. Tea contains several compounds (especially polyphenols) which are believed to have antioxidant capacity. In the present study, a handy-assay procedure to measure simultaneously the TPC and the antioxidant capacity in teas using the FCR was developed. A spectrophotometric procedure using the FCR was undertaken to evaluate simultaneously the TPC and the antioxidant capacity, expressed in Trolox equivalents antioxidant capacity (TEAC), of 32 samples of 7 different types of teas. For comparison purposes, the antioxidant activity of the same samples was determined using the CUPRAC (cupric reducing antioxidant capacity) reagent. Finally, the antioxidant capacity in a cup of tea (200 mL) obtained with the FCR and expressed in ascorbic acid equivalents (AAEC) was performed. The TEAC values obtained with FCR presented a good positive correlation with the CUPRAC method (r² = 0.853), suggesting that both reagents can be used to quantify the antioxidant capacity. The TEAC and CUPRAC values also showed good agreement with the TPC (r² = 0.969 and r² = 0.809, respectively) indicating that the antioxidant capacity should be due to the presence of polyphenols. The results obtained and the calculation strategy used may be an easier way to present the antioxidant capacity values to the final consumer who is most commonly unfamiliar with this important concept.