Free radical scavenging activity was determined from the inhibition of the colored free radical, DPPH at 520 nm. DPPH was dissolved in methanol to 0.2 mM obtaining the stable free radical DPPH . Various concen- trations of the crude extract solution in methanol was mixed in the ratio 1:1 with the DPPH solution in a 96-well microplate. Appropriate controls were run in each series. Fresh DPPH solution was prepared daily. Each crude extract was tested in triplicate at 5 concentrations, in which a 50% fall in absorbance of the DPPH was calculated. The absorbance of the reaction mixture at 520 nm
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was measured after 30 min storage from light using a microplate spectrophotometer. The IC50 (concentration causing 50% inhibition) value of each extract was determined and calculated. BHT, BHA, and vitamin C were used as the reference standards for antioxidants (Manosroi et al., 2010a)