Antioxidant Capacity Evaluation of Fruit Extracts

The DPPH• radical scavenging activity of FS and NFS extracts was determined according to Chiellini et al. [40 (link)]. The absorbance was recorded at 517 nm, and the extract concentration corresponding to 50% of DPPH inhibition (EC₅₀) was measured according to Gabriele et al. [41 (link)]. The oxygen radical absorbance capacity (ORAC) of FS and NFS extracts was determined as described by Gabriele et al. [39 ]. AAPH was used as a peroxyl radicals generator and fluorescein as the probe. Fluorescein fluorescence decay was read at λ_ex 485 nm and λ_em 514 nm using a VictorTM X3 Multilabel Plate Reader (Perkin Elmer, Waltham, MA, USA). Results were expressed as ORAC units (µmol TE/g FW) using Trolox as the reference standard. The ferric-reducing antioxidant power (FRAP) assay was used to evaluate the ability of FS and NFS extracts to reduce ferric iron (Fe³⁺) to ferrous iron (Fe²⁺) [42 (link)]. The absorbance was measured at 593 nm (Perkin Elmer UV/VIS Lambda 365, Waltham, MA, USA), and results were expressed as Fe²⁺ equivalents (µM) using a standard curve of FeSO₄·7H₂O. The Fe²⁺ chelation ability of FS and NFS extracts was determined as described by Chelucci et al. [42 (link)]. The absorbance was read at 562 nm (Perkin Elmer UV/VIS Lambda 365, Waltham, MA, USA), and results were expressed as EC₅₀ values referring to the extract concentration corresponding to 50% of Fe²⁺ chelation.