Pomegranate Iron (III) Reducing Antioxidant Capacity (iRAC) Compared to ABTS Radical Quenching

Pomegranate juice (PJ) has total antioxidant capacity (TAC) which is reportedly higher compared to other common beverages. This short study aimed to evaluate the TAC of commercial PJ and pomegranate fruit in terms of a newly described iron (III) reducing antioxidant capacity (iRAC) and to compare with ABTS free radical quenching activity. Commercial PJ, freeze-dried pomegranate, and oven dried-pomegranate were analyzed. The total phenols content (TPC) was also assessed by the Folin-Ciocalteu method. The calibration results for iRAC were comparable to ABTS and Folin-Ciocalteu methods in terms of linearity (R2 > 0.99), sensitivity and precision. The TAC for PJ expressed as trolox equivalent antioxidant capacity (TEAC) was 33.4 ± 0.5 mM with the iRAC method and 36.3 ± 2.1 mM using the ABTS method. For dried pomegranates, TAC was 89–110 mmol/100 g or 76.0 ± 4.3 mmol/100 g using iRAC and ABTS methods, respectively. Freeze-dried pomegranate had 15% higher TAC compared with oven-dried pomegranate. In conclusion, pomegranate has high TAC as evaluated by the iRAC and ABTS methods, though variations occur due to the type of cultivar, geographic origin, processing and other factors. The study is relevant for attempts to refine food composition data for pomegranate and other functional foods.