Evaluation of TRAP and FRAP Methods for Assessing Total Antioxidant Capacity of Rat Serum

Because of the difficulty in measuring each antioxidant component separately and the interactions among different antioxidant components in the serum or plasma, several methods have been developed to assess the total antioxidant capacity. The objective of the present study was to evaluate and compare the total Radical-Trapping Antioxidant Potential (TRAP) and Ferric Reducing Ability of Plasma (FRAP) methods for assessing the total antioxidant capacity of rat serum. Serum samples were obtained from 10 healthy male Wistar rats (8 weeks, 190 ± 5 g). The total TRAPs were determined based on the protection afforded by antioxidants against the decay of R-Phycoerythrin fluorescence emission during a controlled peroxidation reaction initiated by AAPH. The FRAP was determined based on the reduction of the ferric tripyridyltriazine [Fe(III)–TPTZ] complex to the ferrous tripyridyltriazine [Fe(II)–TPTZ] at low pH. The Fe(II)–TPTZ complex gives a blue color with an absorbance maximum at 593 nm. The final results were converted to mol Trolox equivalents/L. The total antioxidant capacity of rat serum, measured by TRAP or FRAP methods was stable over a 4-week time period. The value of total antioxidant capacity of rat serum determined by TRAP method was three folds higher than that of FRAP method. The main contributors to rat serum TRAP and rat serum FRAP were albumin (30.33%) and uric acid (57.13%) respectively. The amount of contribution of -carotene in rat serum TRAP was 7.22 % and in rat serum FRAP was 0%. The antioxidant capacity of an antioxidant against a free radical does not necessarily equal with its ability to reduce Fe(III) to Fe(II).