2.3.4. Assay of DPPH radical scavenging activity
The DPPH radical scavenging activity was assayed according to the method of
Shimada et al. (1992) with some modifications. Briefly, 2 ml of DPPH solution
(0.2 mM DPPH in methanol) was mixed with 2 ml of sample (0.05–2 mg/mL). The
mixture was shaken vigorously and allowed to stand at room temperature for
30 min. Then, the absorbance of the mixture was measured at 517 nm. VC was used
as the positive control. The DPPH radical scavenging activity was calculated by the
following formula:
Scavenging activity ð%Þ¼½1 ðA1 A2Þ=A0 100 ð3