Antioxidant and Lipoxygenase Inhibition Activities of Ultrasound-Assisted Extracts from Prokupac Grape Skins

Abstract

The antioxidant and anti-inflammatory properties of grape skin extracts derived from the indigenous Serbian grape variety Prokupac, using ultrasound-assisted extraction (UAE), are showed in this contribution. Extraction was performed with 50% ethanol, absolute ethanol, and ethyl acetate, yielding values between 4.9% and 9.8%. The highest total phenolic content (TPC) was obtained for extracts in 50% ethanol without prior maceration - PSE0 (22.4 mg GAE/g GSE), followed by ethyl acetate - PSE3 (9.8 mg GAE/g GSE), while ethanol-based extracts contained markedly lower phenolic levels. Antioxidant activity, assessed by DPPH, ABTS, and FRAP assays, confirmed that PSE0 exhibited the strongest radical scavenging ability (SC50 = 0.3 μg/mL),comparable to standard antioxidants, whereas PSE3 also showed significant activity. Anti-inflammatory activity, evaluated through lipoxygenase (LOX) inhibition, demonstrated that PSE0 (IC50 = 7.9 μg/mL) outperformed quercetin and approached NDGA, the reference inhibitor. These results highlight grape skins, a winemaking by-product, as a sustainable source of bioactive compounds with potential functional food and nutraceutical applications.