This study aimed to evaluate the chemical composition, in vitro antioxidant activity, and hypoglycemic activity of extracts from the stems, leaves, and flowers of Dendrobium devonianum Paxt. (D. devonianum), to elucidate the metabolic basis underlying differences in bioactivity using metabolomics, and to provide a theoretical basis for the high-value utilization of D. devonianum resources and the development of functional foods.

Stems, leaves, and flowers of D. devonianum were extracted using varying concentrations of ethanol (0, 60%, and 100%). The content of total sugars, total phenolics, and total flavonoids were determined. Antioxidant activities including DPPH, ABTS⁺ radical scavenging capacities and ferric reducing antioxidant power (FRAP) were assessed, along with α-glucosidase inhibitory activity. High-performance liquid chromatography (HPLC) was employed to quantify phenolic compounds. Untargeted metabolomics, combined with partial least squares discriminant analysis (PLS-DA) and KEGG pathway enrichment analysis, was performed to compare metabolic profiles and identify key differential metabolites and pathways among the different plant parts.

Stem extracts exhibited the highest total sugar content, whereas flower extracts demonstrated significantly higher total phenolic and flavonoid contents, as well as stronger antioxidant activities, than stems and leaves. Within the same plant part, the 60% ethanol extract had the highest total flavonoid content, ABTS⁺ scavenging capacity, and FRAP value, while the 100% ethanol extract exhibited the highest total phenolic content and DPPH scavenging capacity. The α-glucosidase inhibitory activities of flowers and leaves were superior to those of stems. HPLC analysis identified 11 phenolic compounds, with the 60% ethanol extract containing the greatest variety and the highest concentration within the same plant part. Metabolomics identified 1 859 metabolites, of which 1 051 were differential metabolites. Metabolite classes such as lipids, organic acids, and their derivatives were significantly correlated with antioxidant and hypoglycemic activities.

The stems, leaves, and flowers of D. devonianum all possessed significant antioxidant and hypoglycemic activities, which were closely related to plant part and extraction solvent. The flowers exhibited the strongest overall bioactivity.