Onion nutritional and nutraceutical composition and therapeutic potential of its phytochemicals assessed through preclinical and clinical studies

Onion ( Allium cepa L.) is widely recognized for its nutraceutical and medicinal benefits. This review explores the nutritional and phytochemical composition of onion, along with the therapeutic potential of its key bioactive compounds, based on existing literature. Preclinical and clinical studies assessed its anticancer, antimicrobial, anti-inflammatory, and antioxidant properties, while therapeutic potential was evaluated using standard criteria. Findings confirm onions are nutrient-rich, containing essential vitamins, minerals, and bioactive compounds. Quercetin reduces oxidative stress, lowers blood pressure, and improves cognitive function, while allicin and quercetin exhibit anticancer effects by inhibiting cancer cell proliferation and promoting apoptosis. Organosulfur compounds enhance immune function and are linked to reduced tumor growth in colorectal cancer patients. Onion-derived compounds demonstrate promising therapeutic properties, warranting further research. This review underscores onion's health benefits and the need for continued investigation into its bioactive compounds for functional food and pharmaceutical development. • Onions are low-calorie, fibre-rich, and packed with vitamins and minerals. • Allicin, quercetin, and sulfur compounds offer key antioxidant properties. • Onions promote heart health by lowering BP and cholesterol, and are antimicrobial. • Onion sulfur compounds may help reduce cancer risk due to anticancer effects.