MÉTODO DE FOLIN CIOCALTEAU ADAPTADO PARA QUANTIFICAR POLIFENÓIS EM EXTRATOS DE ERVA-MATE

MÉTODO ADAPTADO DE FOLIN CIOCALTEAU

Abstract

Yerba mate leaves are traditionally consumed and known by their high concentration of polyphenols. The spectrophotometric method commonly used to analyze Total Polyphenols Content (CFT) is Folin-Ciocalteu, in which a standard curve of gallic acid is used and the absorbance of samples is analyzed using 765 nm wave-length. The aim of this work was to adapt Folin-Ciocalteu method in order to determinate CFT of yerba mate extract reducing reagents use and reaction time, providing efficiency and economy. Therefore, the kinetics of the reaction was studied and a modification of the inclination of the kinetic curve in 30 minutes reaction time was observed. In order to evaluate the adequacy of the reaction time to 30 minutes, standard curves were obtained by three different analysts and the results were compared to 2 hour reaction time analyses, according to Folin-Ciocalteu method. The results were expressed in gallic acid equivalent (EAG). The absorbance results ranged from 0.004 ± 0.004 (0 mg EAG L^-1) to 1.187 ± 0.100 (1000 mg EAG L^-1) for the reaction of 2 hours. In the reaction of 30 minute these values ranged from 0.005 ± 0.004 (0 mg EAG L^-1) to 1.177 ± 0.022 (1000 mg EAG L^-1). These methods were used to quantify the CFT in yerba mate leaves and the results were 58.33 ± 3.90 mg EAG g^-1 (traditional method) and 57.77 ± 2.70 mg EAG g^-1 (adapted method). These results demonstrate the adapted method reproducibility, showing its usefulness to obtain greater efficiency and economy in the analysis.