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Mechanisms and Biomarkers (WG 4) page 26
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usual antioxidant capacity assays are FRAP, TEAC and TRAP assays where the oxidants used
are not necessarily prooxidants. Trolox equivalent antioxidant capacity (TEAC) assay (Miller
et al., 1993) is based on the inhibition of the absorbance of the quite stable radical cation
ABTS° + of ABTS with ferrylmyoglobin radical species generated by the activation of
metmyoglobin with hydrogen peroxide. The assay measures the ability of antioxidants of
given samples to reduce ABTS radical and compared with a reference, i.e. the Trolox, an
hydrosoluble form of α-tocopherol. Ferric reducing ability of plasma (FRAP) assay (Benzie
and Strain, 1996) measures the ability of biological samples to reduce the ferrictripyridyltriazine
(Fe 3+ -TPZ) into Fe 2+ -TPZ reflecting the ability of the antioxidants within the
sample to reduce the reactive species. This method is not suitable for glutathione
determination and was weakly correlated with ORAC assay.
Total Radical-Trapping Antioxidant Parameter (TRAP) is a fluorimetric assay (Ghiselli et al.,
1995) that monitors the rate of peroxidation induced by thermal decomposition of 2,2diazobis-(2-amidinopropane)dihydrochloride
through the loss of fluorescence of the protein
R-phycoerythrin. Also in this assay the lag phase induced by plasma antioxidants is compared
with that induced by Trolox.