2.8. Free radical scavenging activity on a,a-diphenyl-bpicrylhydrazyl
radical (DPPHd)
The antioxidant activity of Tamarind seed coat extracts,
ascorbic acid and BHA was measured in terms of hydrogen
donating or radical scavenging ability, using the DPPHd
method (Brand-Williams, Cuvelier, & Berset, 1995) modified
by Sa´ nchez-Moreno, Larrauri, and Saura-Calixto
(1998). A methanol solution (0.1 ml) of the sample extracts
at various concentrations was added to 3.9 ml (0.025 g/l) of
DPPHd solution. The solution was incubated at room
temperature for 60 min and the decrease in absorbance at
515nm was determined at the end of incubation period
with a Spectrophotometer. The remaining concentration of
DPPHd in the reaction medium was calculated from a
calibration curve obtained with DPPHd at 515nm. The
percentage of remaining DPPHd (DPPHd
R) was calculated
as follows:
%DPPH
R ¼ ½ðDPPHÞT=ðDPPHÞT¼0 100,
where DPPHd
T was the concentration of DPPHd at the time
of 60 min and DPPHd
T ¼ 0 was the concentration of DPPHd
at time zero (initial concentration).
The percentage of remaining DPPHd against the sample/
standard concentration was plotted to obtain the amount
of antioxidant necessary to decrease the initial concentration
of DPPHd by 50% (EC50). Based on the parameter