2.4.2. DPPH assay
The method described by Molyneux (2004) was used to
measure the free DPPH radical scavenging activity with some
modifications. An aliquot (50 ll, 5 mg/ml) was added to 2 ml
of 100 lM methanolic solution. Absorbance was measured at
517 nm at 0 and 15 min incubation at room temperature.
Percent inhibition activity was calculated:
%inhibition ¼ ððADPPH AsampleÞ=ADPPHÞ 100%
where ADPPH – absorbance of DPPH solution in the absence
of sample or standard, and Asample – absorbance of a DPPH
solution with a tested sample or positive control. The antiradical
activity (EC50) defined as the concentration of the sample
resulting in 50% inhibition was calculated from a
dose–response plot, in which % inhibition against extract (in
volumes from 5 to 50 ll) concentration was plotted. Tests were
carried out in triplicate.