The assay was performed by a slightly modified protocol
of Re et al. [11]. ABTS solution (7 mM) was reacted
with ammonium persulphate (2.45 mM) solution to produce
a dark coloured solution containing ABTS radical
cations. The initial absorbance was measured at 745 nm.
This stock solution was diluted with methanol to give a
final absorbance value and equilibrated at 30˚C. The decrease
in absorbance was measured exactly one minute
after mixing the solution, up to six minutes. The final
absorbance was noted. The percentage inhibition was
calculated according to the formula:
% inhibition = [(Acontrol – Asample)/Acontrol] × 100%