Comparison of ABTS/DPPH assays for the detection of antioxidant capacity in foods

The present study aimed to evaluate two different spectrophotometric assays for detection of vitamin C equivalent antioxidant capacity (VCEAC) of foods. Fifty popular, antioxidant‐rich fruits, vegetables and beverages in the U.S. diet were analyzed for their 2,2′‐azino‐bis‐3‐ethylbenzthiazoline‐6‐sulphonic acid (ABTS) anion radical scavenging activity (ABTS assay) and their ability to reduce 1,1‐diphenyl‐2picrylhydrazyl (DPPH) radical (DPPH assay). The highest VCEAC was detected for strawberry with 520.7 ± 39.3 mg vitamin C equivalent (VCE)/100 g by DPPH assay and for blueberry with 476.6 ± 28.9 mg VCE/100 g by ABTS assay. Although the order differed slightly, both assays identified the same top ten VCEAC food items in the U.S. diet based on fresh weight as blueberry, plum, strawberry, red cabbage, red wine, grape, cherry, green tea, broccoli and apple. VCEAC of 50 food items detected by ABTS assay showed a strong positive relationship with VCEAC measured by DPPH assay (r = 0.886, p<0.001). VCEAC detected by ABTS assay demonstrated a stronger positive association with the USDA database for the oxygen radical absorbance capacity (ORAC) (r = 0.473, p < 0.01). ABTS assay was superior to DPPH assay in reflecting the antioxidant levels of foods containing hydrophilic, lipophilic, high‐moisture, or high‐pigmented nutrients. Hence, ABTS assay may be more useful than DPPH assay in detecting VCEAC in foods. Grant Funding Source : Supported by Beginning Grant in Aid (BGIA) No. 0865092E from the American Heart Association and University of Connecticut Faculty Large Grant