The free radical-scavenging activity was carried out using a
spectrophotometer by the improved ABTS radical cation decolorization
method as described (Cai et al., 2004; Wojdylo et al.,
2007). ABTS radical cation (ABTS•+) was produced by reacting
7.0 mmol/L ABTS solution with 2.45 mmol/L potassium persulfate
at 2:1 (v/v) and allowing the mixture to stand in the dark at room
temperature for 16 h prior to use. The ABTS•+ solution was diluted
with 80% ethanol to yield an absorbance of 0.700 ± 0.02 at 734 nm.
The ABTS•+ solution (4.0 mL, absorbance of 0.700 ± 0.02) was added
to 0.1 mL of appropriately diluted sample and was mixed thoroughly.
The reaction mixture was stored at room temperature
for 6 min, and absorbance was immediately measured at 734 nm.
Trolox standard solution (final concentration 50–700 mol/L) was
prepared and assayed under the same conditions. Results were
expressed in terms of mmol TEAC.