Fresh FRAP reagent
was prepared daily, by mixing 10 volumes of acetate buffer
(300 mM, pH 3.6), one volume of TPTZ (2,4,6-tripyridyl-s-triazine)
solution (10 mM TPTZ in 40 mM HCl), and one volume of
FeCl36H2O solution (20 mM). The reagent was warmed to 37 C.
An aliquot of samples (10–50 ll) was mixed with 950–950 ll of
FRAP reagent. The change in absorbance was measured at
593 nm after initial mixing and up to 90 min. Aqueous solutions
of FeSO47H2O were used for calibration of the FRAP assay and antioxidant
power was reported as lmol trolox/g dwt of polysaccharide
sample.