The dose-response curve obtained by analysis
of a range of concentrations of antioxidant compounds,
Trolox standards and selected food extracts, at
selected time points in the reaction, 1, 4 and 6 min, in
some cases, was plotted as the percentage inhibition of
the absorbance of the ABTS•1 solution as a function of
concentration of antioxidant (Fig. 4). The concentration
of antioxidant giving the same percentage inhibition of
absorbance of the radical cation at 734 nm as 1 mM
Trolox was calculated in terms of the Trolox equivalent
antioxidant activity at each specific time-point. To calculate
the TEAC, the gradient of the plot of the percentage
inhibition of absorbance vs. concentration plot for
the antioxidant in question is divided by the gradient of
the plot for Trolox. This gives the TEAC at the specific
time point and the calculated results for the flavonoids,
carotenoids, some plasma antioxidants, and a representative
fruit and beverage sample are given in Table 1.