Free radical-scavenging ability of grape seeds extracts was
determined by use of a stable 2.2-diphenyl-2-picrylhydrazyl radical
(DPPH*) (Von Gadow, Joubert, & Hansmann, 1997). Free radical
working solutions were prepared dissolving the stock solution of
DPPH* (24 mg DPPH in 100 ml ethanol) with ethanol to get an
initial absorbance of 1.10 0.02. An aliquot of 100 mL of the sample
was placed in a tube and reacted with 2 mL of DPPH* working
solution. The mixturewas vigorously shaken and left to stand in the
dark for 24 hours at room temperature. The decrease in absorbance
was measured at 515 nm after 24 hours versus blank solution
(ethanol). Lower absorbance of the reaction mixture indicates
higher free radical- scavenging activity. All determinations were
performed in triplicate. The affinity of the test material to quench
DPPH radicals (% Inhibition of DPPH) was calculated using the
following equation: