3.5.2. Ferric reducing/antioxidant power (FRAP)
The FRAP assay is a method of measuring the ability of reductants
(antioxidants) to reduce Fe3+–Fe2+ (Benzie & Strain, 1996).
The formation of blue coloured Fe2+–TPTZ complex (Fe2+ tripyridyltriazine)
increases the absorbance at 593 nm. The FRAP values of
the extracts of gac fruits factions are shown in Table 4. The FRAP
value of different fraction extracts indicated that the aril fraction
had the greatest reducing power, followed by peel, pulp and then
seed. The aril extract gave high FRAP values; these may be due to
their higher TPC. According to Butsat and Siriamornpun (2010)
TPC was positively associated with the FRAP value as shown in
the bran fraction of rice. In addition, the extracts at the immature
stage had the lowest FRAP value, whereas the reducing power of
the antioxidant capacity decreased from the immature stage to the
ripe stage. The different fractions from the four parts showed significant
(p < 0.05) difference in the FRAP values, indicating that
the fractions significantly influenced the ferric reducing power.