Isolation and characterization of flavonoid fractions from orange peel with antioxidant properties

Background: Citrus sinensis peel is an abundant agro-industrial byproduct rich in flavonoids and a potentially underexploited source of natural antioxidants. This study aimed to extract, characterize, and evaluate the antioxidant potential of flavonoid fractions from orange peel for food and pharmaceutical applications. Methods: Dried Citrus sinensis peel underwent hydroalcoholic extraction (ethanol: water, 1:1 v/v) for 72 hours by column chromatography purification. Characterization utilized HPLC, UV-Vis, and FTIR spectroscopy. Antioxidant activity was quantified via DPPH radical scavenging and FRAP assays. Results: HPLC identified hesperidin as the predominant flavonoid (52.4 mg/g extract), followed by naringin (18.9 mg/g), rutin (13.7 mg/g), and quercetin (8.5 mg/g). Total flavonoid content was 4.29 mg quercetin equivalents/g extract. The extract demonstrated concentration-dependent DPPH scavenging (32.4–88.6% at 0.5–2.5 mg/ml; IC₅₀=1.21 mg/ml) and strong ferric reducing capacity (1655±18 µmol Fe(II)/g). FTIR confirmed characteristic flavonoid functional groups. Conclusions: Citrus sinensis peel extract exhibits significant antioxidant activity, validating its potential as a sustainable natural antioxidant source for food preservation and pharmaceutical formulations.