Widely Targeted Metabolomics Reveals Differences in Secondary Metabolites in Oats With Different Grain Hardness

ABSTRACT Grain hardness is a crucial factor influencing the processing quality of cereals. This study utilized UHPLC–MS/MS technology to explore novel changes in metabolites associated with grain hardness in the oat cultivars HX317 and HX320. By integrating metabolomics with multivariate statistical methods, we identified 409 secondary metabolites and demonstrated the differences in metabolite profiles between seeds exhibiting varying levels of hardness. The synergistic action of flavonoids cirsilineol (4′,5‐dihydroxy‐3′,6,7‐trimethoxyflavone) and swertiajaponin suggests a potential mechanism for regulating reactive oxygen species accumulation, which may subsequently induce ⍺‐amylase degradation of branched starch through gibberellic acid and abscisic acid pathways, thereby potentially influencing grain hardness. These findings enhanced our understanding of the metabolic mechanisms underlying oat grain hardness and provided a theoretical basis for improving oat processing quality.