Characterization of antioxidant qualities and exploration of mechanisms in different colored onions: Insights from metabolomics and systems biology

Onion color correlates with nutritional value; however, systematic studies assessing antioxidant properties across different colored varieties remain limited. This research integrates chemometrics, metabolomics, and systems biology to evaluate antioxidant quality and underlying mechanisms. Purple onions exhibited the highest total phenolic and flavonoid content, along with superior water-soluble free radical scavenging and reduction capacity. In contrast, white onions excelled in scavenging fat-soluble free radicals and superoxide anions. Key marker metabolites identified included fatty acyls for purple onions, flavonoids for white onions, and carboxylic acids for yellow onions. The in vivo antioxidant effects were mediated through core targets SRC, AKT1, EGFR, MMP9, and TNF, primarily via the VEGF signaling pathway, which was preliminarily validated through molecular docking studies. These findings elucidate the metabolic basis of color-related antioxidant activity, thereby supporting the development of functional foods. • Purple onion tops in water-soluble antioxidants; white excels in fat-soluble. • Metabolomics and bioinformatics decode antioxidant networks of onions. • LEfSe analysis identified biomarkers of onion with different colors.