Onions (Allium cepa L.) comprise a valuable vegetable crop in many countries. Modern scientific research has shown that onions possess many biological activities, including antibacterial, anticancer, hypoglycemic, hypolipidemic, antiplatelet aggregation, and antioxidant activities. The goal of this study was to investigate the impact of total onion polyphenols on antioxidant and xanthine oxidase (XO) inhibitory activities. Total onion polyphenols showed significant antioxidant activity in DPPH, FRAP, and OH-assays (IC50 [mg/mL]), 43.24, 560.61, and 12.97, respectively). In a X/XO system, antio...