Wenhui Zhou

Brewing temperature and duration jointly modulate the sensory perception, functional properties, and chemical composition of herbal tea infusions, yet their integrated effects on Cyclocarya paliurus tea remain poorly understood. Here, cold-brewed (4 °C) and hot-brewed (90 °C) C. paliurus infusions prepared over a 5 min–2 h time gradient were systematically characterized using a multi-platform analytical strategy. Brewing mode and time produced clearly differentiated quality profiles: hot brewing yielded darker infusions with stronger bitterness and astringency, higher phenolic and flavonoid contents, and greater 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging capacities, whereas cold brewing produced lighter, milder infusions with more gradual time-dependent compositional changes. Volatile and non-volatile profiles were clearly separated between the two brewing modes, and their temporal patterns indicated compound-specific temperature- and time-dependent responses rather than a generalized increase in extraction efficiency at elevated temperature. In total, 61 volatile features and 3666 metabolite features were annotated, from which 50 core differential metabolites were screened; exploratory treatment-level correlation analysis linked tentatively annotated gossypetin 8-glucuronide to radical-scavenging capacity, kaempferol 3-O-arabinoside and sericoside to bitterness-related responses, and epoxypheophorbide a to color variation. These findings clarify how brewing temperature and time jointly shape the quality of C. paliurus tea infusions and provide candidate chemical markers to guide the selection of brewing conditions and the development of differentiated C. paliurus-based herbal beverages. As a single commercial batch of C. paliurus tea was examined, these findings should be interpreted within the context of the tested material and brewing conditions.

Brewing temperature and duration jointly modulate the sensory perception, functional properties and chemical profiles of herbal tea infusions, yet their integrated effects on Cyclocarya paliurus tea remain poorly understood. In this study, cold-brewed (4 °C) and hot-brewed (90 °C) C. paliurus infusions were prepared across a time gradient from 5 min to 2 h, and systematically characterized via a multi-platform analytical strategy.Hot brewing produced darker infusions with stronger bitterness and astringency, higher levels of phenolics and flavonoids, and greater DPPH(2,2-diphenyl-1-picrylhydrazyl ) and ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging capacity, whereas cold brewing resulted in lighter appearance, milder taste and more gradual time-dependent compositional changes. A total of 61 volatile features and 3666 metabolite features were annotated, with 50 core differential metabolites screened. Representative metabolites including gossypetin 8-glucuronide, kaempferol 3-O-arabinoside, sericoside and epoxypheophorbide a were statistically associated with antioxidant, bitterness and color traits, respectively.These results demonstrate compound-specific temperature- and time-dependent responses rather than simplistic greater extraction under high temperature, providing chemical clues for brewing optimization and development of differentiated C. paliurus-based herbal beverages.

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.

Cyclocarya paliurus leaves are widely consumed as “sweet tea”, yet mature leaves harvested after spring remain underutilized despite their potential health-promoting value. This study aimed to clarify how harvest month modulates volatile signatures and functional bioactivities of C. paliurus leaves across the growing season. Leaves collected from May to September (Q5–Q9) were extracted with water and characterized by spectrophotometric quantification of major non-volatile constituents (TPC, TFC, TP, and TSC), SPME–GC–MS profiling of volatile organic compounds (VOCs), DPPH radical scavenging assays, and BSA-based glucose/fructose glycation models; multivariate and correlation analyses were further applied to link chemical dynamics with bioactivities. Antioxidant capacity exhibited clear harvest-stage dependence, with Q9 and Q6 showing the strongest DPPH scavenging and the lowest IC₅₀ values (0.119 and 0.222 mg/mL, respectively). Anti-glycation activity displayed a similar temporal pattern: in both Glu–BSA and Fru–BSA systems, Q6 and Q9 consistently achieved the most pronounced inhibition of AGEs accumulation, exceeding 70% at weeks 3–4. VOCs underwent substantial seasonal remodeling, characterized by alkene predominance in Q6 (74.00%), alcohol enrichment in Q7 (38.90%), and a transient increase of alkanes in Q8 (22.32%), with ketones recurring at early and late stages. Correlation analysis and a three-phase schematic model collectively suggest that functional differentiation is driven by coordinated interactions between the non-volatile matrix (notably flavonoids) and stage-specific volatile signatures (e.g., alkenes and ketones). Overall, these findings provide a mechanistic basis for precision harvesting and stage-targeted utilization of mature C. paliurus leaves to optimize both bioactivity and aroma quality.