Germination-driven dynamic changes of phenolic compounds in oats and the underlying mechanisms for antioxidation...

Gemination is a promising technology to enhance oats nutritional value, especially reshaping their phenolic profile. This study investigated the time-dependent remodeling of oat phenolic compounds during germination and linked these changes to antioxidant capacity, along with underlying cellular mechanisms. Results demonstrated that the total content of polyphenols increased 4-fold after 9-day germination (4.22 ± 0.20 mg GAE/g). Avenanthramides dominated at 3-day germinated oat, whereas flavonoid C-glycosides, primarily vitexin-2-O-rhamnoside and isovitexin-2-O-arabinoside, emerged as the major phenolic in late stage (days 7-9). These compositional shifts paralleled markedly higher DPPH and ABTS radical scavenging capabilities compared with ungerminated oats (P < 0.05). In the RAW264.7 macrophage model, germinated oat extracts can efficiently reduce intracellular ROS accumulation, restore SOD, GPx, and CAT activities, and upregulate Nrf2, HO-1, NQO-1 expression. Importantly, the AVNs-rich early oat sprouts preferentially engaged AMPK/HO-1 signaling, while flavonoid glycosides-enriched late oat sprouts were more likely to activate PI3K/NQO1 pathway, contributing to enhanced antioxidant response. This work identifies germination endpoints that generate mechanistically distinct oat phenolic signatures and can provide guidance for stage-targeted processing of germinated oats for functional food applications.