COMPARISON OF DIFFERENT ANALYTICAL METHODS FOR ASSESSING TOTAL ANTIOXIDANT CAPACITY OF HUMAN SERUM

Three assays were compared for the determination of total antioxidant capacity in human serum: the oxygen radical absorbance capacity (ORAC) assay, the Randox Trolox-equivalent antioxidant capacity (Randox-TEAC ) assay, and the ferric reducing ability (FRAP) assay. There was a wea k but significant linear correlation between serum ORAC and serum FRAP . There was no correlation either between serum ORAC and serum TEAC or between serum FRAP and serum TEAC. The effect of dilution on the seru m TEAC value and the use of inhibition percentage at a fixed time, wit hout considering the length of inhibition time in the quantitation of results, adversely affected the Randox-TEAC assay. The FRAP assay is s imple and inexpensive but does not measure the SH-group-containing ant ioxidants. The ORAC assay has high specificity and responds to numerou s antioxidants. By utilizing different extraction techniques in the OR AC assay, one can remove senun proteins and also make some gross diffe rentiation between aqueous and lipid-soluble antioxidants. However, th e ORAC assay requires similar to 60 min more than the FRAP or Randox-T EAC assay to quantitate results.