2.6. DPPH and ABTS free radical scavenging capacity
For evaluating the DPPH free radical (DPPH) scavenging activity,
the well-established method was used, based on Li et al.
(2009) with slight modifications. The DPPH stock solution was
prepared by dissolving 20 mg of DPPH in 50 mL of ethanol, and
then 50 mL of deionized water was added. The DPPH working solution
was obtained by diluting stock solution with water/ethanol
(50/50, v/v) mixture to an absorbance of 0.75–0.80 at 515 nm.
1 mL of sample was added into 9 mL of DPPH working solution.
After reaction in dark place for 30 min, the absorbance at 515 nm
was measured. The absorbance of 1 mL of water/ethanol (50/50,
v/v) mixture under the same condition was regarded as the control