DPPH radical scavenging activity was determined using the
method originally developed by Blois (1958) with slight modifications
by Lai et al. (2009). A portion (0.1 mL) of the extract solution
(1.0 mg/mL DMSO) in a test tube was well mixed with 3.9 ml of
methanol and 1.0 mL of a,a-diphenyl-b-picrylhydrazyl (DPPH)
solution (1.0 mmol/L in methanol). The mixture was kept at
ambient temperature for 30 min prior to measurement of the
absorbance at 517 nm. BHA was used as the reference. All
measurements were done in triplicate. The scavenging effect was
derived by the following equation:
DPPHscavengingeffectð%Þ¼
h
1
A517nm;sample=A517nm; control
i
100