This assay gives an indication of the reducing ability of
the plant extract. This assay was developed using the
experimental protocol described by Benzie and Strain
(1996), but modified in terms of time lapse; the reaction
was evaluated at 4, 30 and 60 min. The FRAP reagent
was freshly prepared and contained 1020 μL of 300 mM
sodium acetate pH 3.6, 100 μL of 10 mM TPTZ (Sigma
Chemical), and 100 μL of 20 mM ferric chloride. The
FRAP reagents were mixed with 10 μL aliquots of each
extract. Then the mixture was incubated at 37 ºC for 4,
30 and 60 min; after this time, the absorbance was read
at 593 nm using a UV-Vis spectrophotometer (Unicam
Heλio α). The FRAP value was determined by plotting
in a standard curve produced by the addition of ferrous
sulphate (Merck, Darmstadt, Germany) to the FRAP
reagent. Results were expressed as μmol Fe+2 per gram of
fresh weight (μmol Fe+2 g-1 FW).