2.4.4. Reducing power
The reducing power of the prepared essential oil was determined
according to the method of Oyaizu (1986). Briefly, 1.0 mL of
different concentration sample (0.2e1.0 mg/mL) was mixed with
2.5 mL of a 0.2Mphosphate buffer (pH 6.6) and 2.5 mL of a 1% (w/v)
solution of potassium ferricyanide. The mixture was incubated in
a water bath at 50 C for 20 min. Afterwards, 2.5 mL of a 10% (w/v)
trichloroacetic acid solution was added and the mixture was then
centrifuged at 3000 rpm for 10 min. A 2.5 mL aliquot of the upper
layer was combined with 2.5 mL of distilled water and 0.5 mL of
a 0.1% (w/v) solution of ferric chloride, and absorbance was
measured at 700 nm. BHTwas used as a reference material. All tests
were performed in triplicate and the graph was plotted with the
average of the three determinations.