2.5.4.2. Superoxide radical scavenging activity. The superoxide
anion radical was generated by xanthine/xanthine oxidase system.
Superoxide radical scavenging activity was performed according to
the method described by Arumugam, Subathra, and Ramesh (2010).
In brief, the reaction mixture consisted of 2.70 ml of 40 mmol/l
sodium carbonate buffer containing 0.1 mmol/l ethylenediaminetetraacetic
acid (EDTA) (pH 10.0), 60 ml of 10 mmol/l
xanthine in 25 mmol/l sodium hydroxide solution, 30 ml of 5 mg/ml
bovine serum albumin (BSA), 30 ml of 2.5 mmol/l nitroblue tetrazolium
(NBT) and 60 ml of extracts. The mixture was kept at room
temperature (25 C) for 20 min, and after that 120 ml of xanthine
oxidase (0.04 units/ml) diluted in 50 mmol/l TriseHCl buffer (pH
7.5) was added to start the reaction. The absorbance at 560 nmwas
recorded after 5 min. The solution of 60 ml methanol is used as
a control. The tests were performed in triplicate. Results are
expressed as percentage of inhibition of superoxide radicals.
Percentage of inhibition is calculated using the formula:
Percentage of inhibition ¼
1
As
Ac
100%
where As and Ac are the absorbance values of the test sample and
control, respectively.