Allium cepa peel-derived quercetin and polyphenols: Mechanistic evidence for neuroprotection in epilepsy

Allium cepa peel, commonly discarded as waste, is a rich source of bioactive phytoconstituents with potential therapeutic benefits. Neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, and epilepsy are increasing globally and are associated with oxidative stress, inflammation, and neuronal loss. Due to the limited effectiveness of current treatments, plant-derived compounds are gaining attention for their neuroprotective potential. Onion peels are particularly rich in quercetin, its glycosides, and other flavonoids and phenolic compounds known for their antioxidant and anti-inflammatory properties. This review summarizes existing scientific evidence on the neuroprotective effects of Allium cepa peel, based on studies retrieved from PubMed, Google Scholar, and ScienceDirect. Preclinical studies indicate that onion peel extracts can reduce oxidative stress, modulate inflammation, support mitochondrial function, and improve cognitive performance. Quercetin is identified as the primary active compound, along with minor contributions from other phenolics and sulphur-containing compounds. Overall, Allium cepa peel shows promising neuroprotective potential; however, further human studies are required to confirm its mechanisms and clinical applicability.