Trigueros_2025_Food.Chem.X_29_102794

Onion skin, often discarded during processing, remains rich in bioactive compounds, particularly flavonoids. This study assessed phenolic extraction (37 degreesC, 60 min) from Horcal and Red cultivars, using 70:30 ethanol:water. Extracts were rich in phenolics (103-155 mg/g), mainly quercetin and quercetin-4'-O-glucoside (61-67 %), and showed strong O(2) (.-) (IC(50) = 26-27.7 microg/mL) and (.)NO (IC(50) = 53-56 microg/mL) scavenging. They also inhibited alpha-glucosidase (IC(50) = 2.2-2.3 microg/mL) and aldose reductase (IC(50) = 37-44 microg/mL), while preserving alpha-amylase activity (IC(50) = 932-1126 microg/mL). Both extracts demonstrated anti-inflammatory effects via 5-LOX inhibition (IC(50) = 30.2-47 microg/mL) and anti-neuroinflammatory effects by restoring NO in BV2 cells. They further inhibited tyrosinase (IC(50) = 14.9-15.5 microg/mL) and xanthine oxidase (IC(50) = 15.1-19.2 microg/mL) above acetylcholinesterase (IC(50) = 301-532 microg/mL), with Horcal showing greater potential due to higher phenolic content. Extracts were non-cytotoxic and displayed anti-dermatophytic activity, particularly against T. rubrum and E. floccosum. These results suggest onion skin as a promising resource for bioactive compounds, with potential applications in supplements, functional foods, and nutraceuticals.