Comparative Digestive Behavior, Chemical Profiles, and Antioxidant Activities of Coicis Semen Ultrafine Powder Suspension and Water Decoction During In Vitro Gastrointestinal Digestion

This study compared the digestive behavior, chemical profiles, and antioxidant activity of a Coicis Semen ultrafine powder suspension (CSUP) and water decoction (CSW) during in vitro gastrointestinal digestion using the INFOGEST 2.0 model. Peptide content, lipid profile changes, metabolite profiles, and antioxidant capacity were analyzed by peptide quantification, ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS)-based lipidomics, untargeted metabolomics, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging assays. Chemical similarity and antioxidant-related differences were further evaluated using study-specific exploratory indices, including the Chemical Equivalence Index (CE*), Bioequivalence Index (BE), and Chemical–Biological Deviation Index (CBDI*). Compared with CSW, CSUP exhibited approximately 4–8 times higher measured peptide-related content during gastric digestion and 7–10 times higher measured peptide-related content during intestinal digestion. Lipidomics revealed stage-dependent changes in the relative MS signal proportions of triacylglycerols (TAGs), diacylglycerols (DAGs), and other lipid-related components, with pronounced changes occurring during the intestinal phase. Metabolomics revealed different profiles between CSUP and CSW, with differential metabolites mainly enriched in steroid metabolism and cytochrome P450-related pathways according to pathway enrichment analysis. CSUP showed lower DPPH and ABTS IC50 values and higher BE values, consistent with greater in vitro radical-scavenging activity under the tested conditions, while CBDI* values increased during the early intestinal phase. Overall, CSUP and CSW exhibited different digestion-associated characteristics under the tested conditions, and CSUP showed higher measured peptide-related content and stronger in vitro radical-scavenging activity than CSW. These findings provide comparative information for evaluating different preparation forms of Coicis Semen.