2.4.2.2. ABTS cation decolorization assay. ABTS radical assay was used to
evaluate the ability to scavenge free ABTS radicals, based on the protocol
of Re et al. (1999) with some modifications. ABTS radical cations
(ABTS+) were prepared by reacting a 7.4 mM ABTS stock solution
with 2.45 mM potassium persulphate (1:1, v/v), after which the mixture
was kept overnight (12–16 h) in the dark at room temperature.
The ABTS radical solution was diluted with distilled water to an absorbance
of 1.0–1.2. A 1 ml aliquot of the diluted spice sample was added
to 50 ml of each of the above-prepared radical solutions and protected
from light for 60 min. Absorbance readings were measured using a
spectrophotometer at 734 nm. Results were expressed as μ mol of
trolox equivalents (TE) per g sample from a standard curve developed
with Trolox.