2.5.3. DPPH radical scavenging activity
The antioxidant activity of the extract was measured with the
DPPH method [18] with slight modifications. A solution of
DPPH was freshly prepared by dissolving 6 mg DPPH in 50 mL
methanol (about 0.3 mM). The extract (2.5 mL) with varying
concentrations (60e220 mg/mL) and DPPH solution (2.5 mL)
was mixed together in a test tube. The test tube was then
incubated in the dark for 20 minutes at room temperature.
The decrease in absorbance was measured at 517 nm using a
UVeVIS spectrophotometer. The percentage inhibition of
radicals was calculated using the following formula:
%inhibition ¼ Acontrol Asample 100 Acontrol
where Acontrol is the absorbance of DPPH solution without
extract and Asample is the absorbance of sample with DPPH
solution. The half-maximal inhibitory concentration (IC50)
was reported as the amount of antioxidant required to
decrease the initial DPPH concentration by 50%. All tests were
performed at least in triplicate, and graphs were plotted using
the average of three determinations.