Screening of Metabolite Biomarkers for Antioxidant and Glycosidase Inhibitory Activities from Oat Resources

Oat accessions vary substantially in their bioactive components and associated functional properties, but the metabolites underlying differences in the bioactivities of digested oat samples remain insufficiently characterized. In this study, samples obtained after simulated gastrointestinal digestion of 43 oat accessions were evaluated for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging and α-glucosidase inhibitory activities, and their metabolite profiles were characterized using ultra-performance liquid chromatography–electrospray ionization–tandem mass spectrometry. Eleven differential metabolites were detected between the groups with high and low DPPH radical-scavenging activity, while nine were detected between groups with contrasting α-glucosidase inhibitory activities. Random forest-based feature selection identified tricin 7-O-β-D-glucoside, myricetin 3-O-glucoside, quercetin 3-O-galactoside, and β-sitosterol as candidate markers associated with variation in DPPH radical-scavenging activity. The association of β-sitosterol with the high-DPPH phenotype was interpreted as statistical rather than as evidence of direct radical-scavenging activity. Myricetin 3-O-glucoside, quercetin 3-O-galactoside, and reduced glutathione were identified as metabolic markers associated with α-glucosidase inhibition. The results revealed substantial variation in the in vitro functional properties and metabolite profiles of digested oat samples. These metabolic markers provide a new research basis for the efficient development and utilization of functional products.