Effects of drying methods on the chemical composition and antioxidant activity of Metapanax delavayi by integrating UHPLC-Q-TOF-MS and GC–MS/MS based untargeted metabolomics

Metapanax delavayi is widely consumed as a vegetable and herbal tea in western China; however, the impact of postharvest drying on its chemical composition and bioactivity remains insufficiently characterized. In this study, the effects of three drying methods-shade drying (SD), hot-air drying (HAD), and vacuum freeze-drying (VFD)-on the metabolite profile and antioxidant activity of M. delavayi were systematically investigated using UHPLC-Q-TOF-MS and GC–MS/MS-based untargeted metabolomics, combined with multivariate statistical analysis and KEGG pathway enrichment. A total of 742 non-volatile and 87 volatile differential metabolites were detected across the drying treatments, indicating pronounced processing-induced metabolic alterations. KEGG enrichment analysis revealed that the differential metabolites were mainly associated with flavonoid biosynthesis, amino acid metabolism, galactose metabolism, and glycolysis/gluconeogenesis. Antioxidant assays (DPPH, ABTS, hydroxyl radical scavenging activity, and FRAP) demonstrated significant differences among drying methods, with VFD-treated samples generally exhibiting higher antioxidant capacity. Correlation analysis suggested that phenolic and flavonoid metabolites were major contributors to antioxidant activity. Overall, compared with SD and HAD, VFD showed a greater capacity to preserve phytochemical composition and antioxidant potential. These findings provide a scientific basis for optimizing drying strategies and improving the quality of M. delavayi -derived products.