Assays of Antioxidant Properties

Free radical scavenging activity was assessed by the DPPH assay based on the method of Katalinić et al. (2010). Antiradical activity was defined as the amount of antioxidant necessary to decrease the initial DPPH concentration by 50% (EC₅₀). EC₅₀ was calculated with gallic acid as equivalent; for reasons of clarity, the results were provided as antiradical power (ARP = 1/EC50). For the free radical scavenging activity assessed by the ABTS assay, a previous reported procedure was used (Re et al., 1999). The determination of ferric reducing antioxidant power (FRAP assay) was performed according to the method of Sun et al. (2011). For ABTS and FRAP assays, the radical scavenging activities of the samples were expressed as Trolox equivalent antioxidant capacity.