DPPH assay
2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical
scavenging activity was determined following
Tangkanaku et al. (2006) with some modifications.
Two milliliters of the sample were mixed with 8 ml
methanol for 10 min and then centrifuged at 3,000
rpm for 10 min. Consequently, 3.5 ml of supernatant
were mixed with 0.5 ml of 1.5 μM DPPH radical
(Fluka, Switzerland) methanol solution. The mixture
was shaken and allowed to stand for 30 min at
room temperature. Absorbance of the solution was
measured at 517 nm. A control was prepared using
3.5 ml methanol. Percentage inhibition of DPPH
radical was calculated:
%DPPH radical inhibition = [1 − (Abssample/Abscontrol)]