DPPH free radical-scavenging activity test
The effect of the examined extracts on the content of 1,1-diphenyl-2-picrylhydrazyl
(DPPH·) radicals was estimated according to the modified method
of Hatano and co-workers (1988). The concentration of the DPPH· solution
which was used in the assay was 90 mM (22.5 mL 0.4 mM DPPH· solution
(0.01577 g DPPH· in 100 mL methanol) was diluted with 95% methanol to
100 mL). An aliquot (1.0 mL) of the DPPH· solution (90 mM) was diluted in
2.9 mL methanol, and 0.1 mL of the examined extracts at various concentrations
(0.1, 0.5, 1.0 and 2.0 mg/mL for buckwheat flour extracts and 10, 20, 30
and 40 mg/mL for wheat flour extracts) was added. The mixture was shaken
vigorously and left to stand for 60 min in the dark, then the absorbance was
measured at 517 nm against the blank (without extract) in a Jenway (6405
UV/Vis) spectrophotometer.
IC50 (mg/mL) was defined as the concentration of an antioxidant extract
which was required to quench 50% of the initial DPPH· under the experimental
conditions given. It was obtained by interpolation from linear regression
analysis.
BHT and a-tocopherol were used as controls.