Elevational Metabolic Reprogramming Optimizes Flavonoid Accumulation and Antioxidant Capacity in Chimonobambusa utilis Leaves

Chimonobambusa utilis is a dominant bamboo species in China, yet its leaves remain an underutilized resource despite their significant bioactive potential. To elucidate the metabolic reprogramming of Ch. utilis leaves across an elevational gradient and its link to antioxidant phenotypes, we integrated widely targeted metabolomics with redox profiling of leaves collected from 1150, 1600, and 2000 m in the Qingba Mountains. The mid-elevation (1600 m) group exhibited the most robust antioxidant capacity and the highest total flavonoid content. Metabolomic analysis identified 3113 metabolites across 13 classes, with flavonoids (604 compounds, 22.7% of total abundance) emerging as the predominant secondary metabolites. Pairwise comparisons revealed 1716 differentially accumulated metabolites (DAMs). KEGG enrichment indicated that while the low-elevation (1150 m) group prioritized primary metabolism and upstream phenylpropanoid branches, the high-elevation (2000 m) group was associated with photoprotection and defense responses. In contrast, the mid-elevation environment optimized the flux toward flavonoid biosynthesis while maintaining steady metabolic supply. HPLC quantification further confirmed that key markers—vitexin, hyperoside, orientin, and luteoloside—peaked at 1600 m. Correlation analysis between 423 differential flavonoids and antioxidant indices demonstrated that distinct radical-scavenging activities are driven by specific flavonoid structural motifs. Overall, altitude-driven metabolic remodeling, characterized by a mid-elevation advantage for flavonoid accumulation, dictates the antioxidant plasticity of Ch. utilis leaves.