2.7. Determination of antioxidant capacity
Antioxidant capacity of blackberry leaf mixture extracts was
determined using the DPPH radical scavenging assay described
by Brand-Williams, Cuvelier, and Berset (1995). The free radical
scavenging capacity using the DPPH radical reaction was evaluated
by measuring the absorbance at 515 nm after 30 min of reaction at
room temperature. The results are expressed as lmol Trolox equivalents/L,
using the calibration curve of Trolox (0–1 mM). All measurements
were performed in triplicate.
The Trolox equivalent antioxidant capacity (TEAC) was estimated
by the ABTS radical cation decolorization assay (Re et al.,
1999). The results, obtained from triplicate analyses, are expressed
as Trolox equivalents, and derived from a calibration curve determined
for Trolox (100–1000 lM).
The ferric reducing/antioxidant power (FRAP) assay was carried
out according to a standard procedure by Benzie and Strain (1996).
All measurements were performed in triplicate. Aqueous solutions
of FeSO4 7H2O (100–1000 lM) were used for the calibration
curve and the results are expressed as mM Fe(II).