Allium cepa And Its‐Associated Phytochemicals: Evidence From in Vitro, in Vivo, and Human Studies on Antioxidant Effects

Various pharmacological properties and therapeutic effects were shown for Allium cepa L. (Liliaceae), (A. cepa) or onion and its derivatives including their effects on oxidative stress in different conditions. In this article, an update and comprehensive review of antioxidant effects of A. cepa and A. cepa-associated phytochemicals as well as the underlying molecular mechanisms are provided. The literature on antioxidant effects of A. cepa published between 2015 and the end of July 2025 was searched on database like PubMed, WOS, Science direct and Scopus. A. cepa and its constituents showed antioxidant in various conditions such as cardiovascular, endocrine and metabolic, gastrointestinal and liver, immunological, hematological and autoimmune, urogenital, neurologic and respiratory disorders as well as cancer and neoplasia. The antioxidant effects of A. cepa and its derivatives were achieved by decreasing lipid peroxidation (LPO), malondialdehyde (MDA), nitric oxide (NO), and endothelial nitric oxide synthase (eNOS), inhibiting NADPH oxidase (NOX) activity but enhancing antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GSH-Px), glutathione peroxidase omega (GSPO), thioredoxin reductase (TrxR), glutathione-S-transferase (GST) and glutathione reductase (GR) activities and thiol levels. Therefore A. cepa and A. cepa-associated phytochemicals showed potent antioxidant effects indicating their possible therapeutic value for treatment of disorders associated with oxidative stress.