Growth Month-Associated Variation in Volatile Profiles, Anti-Glycation Capacity, and Antioxidant Activity of...

Cyclocarya paliurus leaves, commonly consumed as "sweet tea", remain underutilized after spring harvest. This pilot study investigated harvest month-associated changes in bioactivity-related properties and volatile profiles of mature leaves collected from May to September (Q5-Q9) at one site in 2024. Aqueous extracts were analyzed for TPC, TFC, TP, TSC, DPPH and ABTS•+ radical scavenging activities, and inhibition of advanced glycation end-products (AGEs) formation in glucose/fructose-BSA models, with aminoguanidine as a positive reference. Dried leaf powders were profiled by SPME-GC-MS for tentative VOC annotation. TPC, TFC, TP, and TSC ranged from 28.04 to 28.87, 15.42 to 40.22, 2.14 to 2.51, and 23.15 to 25.30 mg/g, respectively. Q9 showed the strongest radical scavenging response, with the lowest DPPH and ABTS•+ IC50 values (0.119 and 0.131 mg/mL), while Q6 also exhibited relatively strong activity. Furthermore, Q6 and Q9 exhibited superior advanced glycation end-product (AGE) inhibitory responses, with Q9 being particularly effective in the fructose-BSA model. VOC profiles varied markedly by month, shifting from alkene/terpene predominance in Q5-Q6 to alcohol enrichment in Q7 and renewed alkene/terpene predominance in Q9. Integrated heatmap and Pearson correlation analyses identified clear temporal co-variations and pairwise associations between distinct VOC classes and bioactivity indices. Collectively, these results provide preliminary, site- and year-specific evidence that harvest month is associated with changes in the bioactivity-related properties and aroma-related phytochemical profiles of mature C. paliurus leaves, offering a cautious reference for harvest-stage-oriented utilization.