2.9. Iron(II) chelating ability assay (ICA)
For iron(II) chelating ability assay (ICA) (Wang et al., 2009),
100l of diluted red grape pomace extracts in acetate buffer
(pH 4.6) were mixed with 100l FeCl2·4H2O and placed in each
well. After 5min, 100l of ferrozine solution was added. After
10 min, the absorbance was measured at 562 nm. The percentage of
inhibition of ferrozine-iron(II) complex formation of each sample
was calculated using the formula: ICA (%) = [A0 – (A1 – A2)]/A0 ×100,
where A0, A1 and A2 correspond to absorbance of the control,
sample and blank of the sample, respectively. In A0 the intrinsic
absorbance of iron(II) was subtracted from the initial absorbance.
Results were expressed as %inhibition obtained per mg of dry
residue. Before performing each assay procedure, 200l of sample
were mixed to 200l absolute ethanol p.a. in order to guarantee
the total polyphenolic compounds dissolution.