2.3.2. Assay of superoxide radical scavenging activity
The superoxide radical scavenging activity was performed by the method of Jing
and Zhao (1995) with some modifications. Reaction was carried out in a mixture
containing 4.5 ml of 50 mM Tris–HCl buffer (pH 8.2), 0.4 ml of 25 mM pyrogallol
solution and 1 ml of sample (0.5–5 mg/mL) by incubating at 25 C for 5 min. Finally,
1 ml of 8 mM HCl solution was dripped into the mixture promptly to terminate the
reaction. The absorbance of the mixture was measured at 420 nm. VC was used as
the positive control. The superoxide radical scavenging activity was calculated by
the following formula:
Scavenging activityð%Þ¼½1 ðA1 A2Þ=A0 100 ð1Þ