Widely Targeted Metabolomics Reveals the Bioactive Metabolites and Antioxidant Activities of Chinese Yam (Dioscorea opposita Thunb.) Peel

Chinese yam (Dioscorea opposita Thunb. cv. Tiegun) has been utilized in traditional medicine and as a food source for centuries. However, the metabolite profiles and antioxidant activities of yam by-product peel have not been studied sufficiently. Thus, to effectively identify the active metabolites in yam peel, we employed a UHPLC–MS/MS-based widely targeted metabolomics on Chinese yam peel from loessial soil (LPCY) and sandy soil (SPCY). A total of 1054 metabolites were identified, comprising 379 primary metabolites, 528 secondary metabolites, and 147 other compounds. Notably, multivariate analyses revealed the presence of 143 differentially accumulated metabolites (DAMs) between SPCY and LPCY. Linoleic acid metabolism, phenylpropanoid biosynthesis, plant hormone signal transduction, pyruvate metabolism, and sphingolipid metabolism were the main differentially regulated pathways. The DPPH, ABTS, and FRAP assays demonstrated that the antioxidant activities of LPCY were significantly higher than those of SPCY. Correlation analysis revealed that most DAMs, including phenolic acids, lipids, organic acids, and amino acids, exhibited significant positive correlations with antioxidant activities (r ≥ 0.7, p < 0.05). These results indicate that loessial soil promotes the accumulation of antioxidant-active compounds. Overall, this study suggests that yam peels hold significant potential as a rich natural source of bioactive substances.