To investigate the effect of harvesting time on the aroma quality of Langao green tea, volatile compounds in tea leaves collected in early, middle, and late spring were analyzed using stir bar sorptive extraction coupled with gas chromatography-mass spectrometry (GC-MS). Multivariate statistical analysis and odor activity value (OAV) were applied to systematically identify key differential volatile compounds and aroma-active components. A total of 109 volatile compounds were identified, among which terpenes, alcohols, esters, and ketones were the main ones, collectively accounting for 69% of the total volatile content. Principal component analysis, partial least squares-discriminant analysis, and non-parametric tests revealed 23 key differential compounds (P < 0.05) including cis-linalool oxide (furanoid), linalool, cedrol, and 2-methylbutanal, common across different harvesting periods. Based on absolute quantification and OAV analysis, six key aroma-active components (OAV ≥ 1) were identified: 2-methylbutanal, 1-octen-3-one, linalool, α-cubebene, cedrol, and safranal. Among these, linalool and α-cubebene reached the highest concentrations in middle spring, whereas safranal peaked in late spring. These compounds could be used as important indicators for distinguishing Langao green tea from different harvesting periods. This study provides a theoretical foundation for the precise harvesting and quality control of spring tea. Furthermore, it offers potential strategies for enhancing tea quality through targeted modulation of these key aroma compounds.

This study included four Jinhua white tea samples and five Fu brick tea samples to systematically investigate the differences in sensory quality and chemical composition between the two types of tea. Sensory evaluation results showed that compared with Fu brick tea infusion, Jinhua white tea infusion exhibited a redder color with a sweet, fruity aroma and a sweet, mild/mellow taste profile. A total of 130 compounds were identified in the tea samples using a metabolomics approach based on liquid chromatography-mass spectrometry (LC-MS), including 8 alkaloids, 9 amino acids, 13 dimeric catechins, 16 N-ethyl-2-pyrrolidinone-substituted flavan-3-ol (EPSF), 15 flavanols, 31 flavanols and flavanol-O-glycosides, 2 flavonoids, 2 lipids, 8 organic acids, 11 phenolic acids, 7 catechin B-ring cleavage derivatives, and 8 other compounds. Partial least squares-discriminant analysis (PLS-DA) and heatmap analysis revealed significant differences in chemical composition between Jinhua white tea and Fu brick tea. Among these, 78 significantly differential compounds were identified (P < 0.05). Amino acid content was generally higher in Jinhua white tea than in Fu brick tea. Jinhua white tea had lower levels of esterified catechins (epigallocatechin gallate, epicatechin gallate, gallocatechin gallate, and catechin gallate) but higher levels of non-esterified catechins (epicatechin and epigallocatechin) than Fu brick tea. The contents of catechin dimers (theaflavins, theasinesins, and procyanidins), as well as those of 4 differential catechin derivatives with B-ring cleavage, were generally higher in Jinhua white tea than in Fu brick tea. The contents of 12 EPSFs were significantly lower in Jinhua white tea than in Fu brick tea. The levels of flavanols and flavanol-O-glycosides were lower in Fu brick tea than in Jinhua white tea. The contents of caffeine and guanylate (GMP) were both significantly higher in Jinhua white tea than in Fu brick tea. This study provides a theoretical basis for clarifying the health benefits of Jinhua white tea.

To investigate the effects of anaerobic treatment at different withering degrees on the components and taste quality of γ-aminobutyric acid (GABA)-enriched white tea, tea samples subjected to anaerobic treatment after withering to water contents of 60%, 50%, and 40% were analyzed using sensory evaluation according to the national standard procedure and using metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Exactive/MS). The results showed that the infusion of tea processed with anaerobic treatment at a fresh leaf water content of 60% exhibited a bright apricot-yellow color and a rich sweet-fruity aroma. A total of 151 compounds were identified across all samples, including 19 amino acids, 11 catechins, 15 dimeric catechins, 16 alkaloids, 32 flavonoid glycosides, 8 N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs), 13 phenolic acids, 9 organic acids, 2 aroma glycosides, 16 lipids, and 10 other compounds. The partial least squares-discriminant analysis (PLS-DA) and One-way analysis of variance (ANOVA) results indicated significant differences in the chemical composition of white tea processed at different withering degrees. In total, 125 compounds exhibited significant inter-group differences (P < 0.05). The highest GABA content was found in tea subjected to anaerobic treatment at a fresh leaf water content of 60%. The levels and proportions of amino acids in GABA-enriched white tea fluctuated across different withering degrees. Notably, the contents of catechins, proanthocyanidin dimers, and most flavonoid glycosides significantly decreased after anaerobic treatment, while the levels of theasinensins and theaflavin-3-gallate significantly increased. Additionally, metabolic pathway enrichment analysis revealed that anaerobic treatment at varying withering degrees significantly affected flavonoid and flavonol biosynthesis, as well as alanine, aspartate, and glutamate metabolism in GABA-enriched white tea. This study provides a theoretical basis for the production of GABA-enriched white tea.

To ascertain the influence of storage time on the chemical composition of compressed Shoumei white tea, metabolomics based on ultra-high performance liquid chromatography-quadrupole-orbitrap mass spectroscopy (UPLC-QExactive-MS) was applied to investigate the chemical composition of compressed white tea with different storage periods (3-14 years). A total of 148 chemical compounds were identified including 12 catechins, 12 dimeric catechins, 16 N-ethyl-2-pyrrolidinol-substituted flavanol (EPSF), 17 alkaloids, 11 amino acids, 4 flavonoid aglycones, 30 flavonoid glycosides, 4 aroma glycosides, 11 phenolic acids, 7 organic acids, 14 lipids, and 10 others. Using partial least squares-discriminant analysis (PLS-DA) and heatmap analysis, we selected 145 significantly differential compounds among white tea with different storage periods, which indicated that the chemical composition greatly changed with storage time. The contents of catechins, dimeric catechins, amino acids, phenolic acids, and organic acids decreased, whereas the contents of EPSFs, alkaloids, lipids and flavanol aglycones increased. EPSF content in white tea produced in 2020-2013 was strongly correlated with storage time with a correlation coefficient of 0.882. This study provides a theoretical basis for scientific storage of white tea.

In this study, the difference in the chemical composition among the representative types of Yunnan white tea, Yun Baihao, Yueguangbai grade Ⅰ and Ⅱ of Baimudan and Yun Shou were investigated by metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Orbitrap-MS). A total of 120 compounds were identified, including catechins, dimeric catechins, amino acids, alkaloids, phenolic acids, organic acids, aroma glycosides, flavonoid glycosides, N-ethyl-2-pyrrolidinone-substituted flavan-3-ols, and lipids. Partial least squares-discriminant analysis (PLS-DA) and heatmap analysis showed that there were distinct differences in the chemical components among the different types of Yunnan white tea. A total of 76 significantly differential compounds were among these types (P < 0.05). The contents of catechins, dimeric catechins, alkaloids, phenolic acids, and theanine were higher in white tea from younger tea leaves; some amino acids and myricetin glycosides were richer in Baimudan, while the contents of apigenin glycoside, kaempferol glycoside, quercetin glycoside and lipid compounds were relatively high in Yunshou. This study can provide a theoretical basis for the studies of sensory quality, nutritional value and grade discrimination of Yunnan white tea.

In order to explore the protective effect of Yongchun Foshou tea extracts on ulcerative colitis (UC) and the key bioactive compounds involved, we established a mouse model of UC induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) and intragastrically the mice with the water extracts of clean-aroma, strong-aroma and aged-aroma Yongchun Foshou oolong tea (200 mg/(kg·d)). We evaluated the effects of these three tea extracts on body mass, colon mass per unit length and pathological colon tissue as well as the serum levels of interleukin (IL)-6, IL-10, IL-1β, and tumor necrosis factor α (TNF-α) in mice with ulcerative colitis. Compared with the model group, body mass, colon mass per unit length, and pathological colon tissue were improved in the mice treated with each of the three tea extracts. There was no significant difference in body mass in the mice treated with the water extracts of strong-aroma and aged-aroma oolong tea for 5-7 days after UC induction compared with those before UC induction (P > 0.05). The mice treated with clean-aroma and strongaroma tea extracts showed a significant reduction in colon mass per unit length (P < 0.05 and P < 0.01). Each of these tea extracts reduced the degree of inflammation in mouse colon tissue, significantly increasing the concentrations of the antiinflammatory cytokine IL-10 (P < 0.05 and P < 0.001). The concentrations of the pro-inflammatory cytokines IL-1β and IL-6 were significantly decreased in the mice treated with strong-aroma tea extract (P < 0.05). The correlation analysis of the major compounds in the tea extracts and inflammatory cytokines revealed that flavone glycosides and N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF) were negatively correlated with three pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α). On the other hand, theanine, catechins, and flavone glycosides were significantly positively correlated with IL-10 (P < 0.05). In conclusion, the water extracts of the three aroma types of Yongchun Foshou oolong tea have an ameliorative effect on acute ulcerative colitis. Strong-aroma tea extract is the most effective among these extracts, and the polyphenols in the extract may play an important role.

In order to investigate the changes in the chemical composition of black tea during storage, we analyzed sun-dried black tea stored for 0, 1, 3 and 4 years by metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Orbitrap/MS). A total of 82 compounds were identified, including six catechins, nine dimeric catechins, five amino acids, eight alkaloids, eight phenolic acids, three organic acids, two aroma precursors, six N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF), twenty flavonol/flavone glycosides, ten lipids and five other compounds. Partial least squares discriminant analysis (PLS-DA) and heatmap analysis showed that the chemical composition of sun-dried black tea of different ages was greatly different, with 66 significantly differential compounds being identified between groups (P < 0.05). The contents of catechins, dimeric catechins, amino acids and most flavonol-O-glycosides decreased after storage, while the contents of caffeine, flavone glycosides and six EPSF compounds increased. The Pearson correlation coefficients of the contents of EPSF compounds with storage time were 0.802–0.986, indicating that the contents of EPSF compounds increased in a linear manner during storage. This study can provide a theoretical basis for the elucidation of the chemical composition of sun-dried black tea and for its scientific storage.

In order to investigate the influence of different roasting degrees on the quality and chemical composition of Rougui rock tea (Camellia sinensis (L.) O. Kuntze cv. Rougui), the non-volatile chemical compositions of tea samples processed at different roasting temperatures (low fire: 100 ℃, medium fire: 120 ℃, high fire: 140 ℃) and for different time periods (2, 4, 6, 8 and 10 h) were systematically investigated by metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Exactive/MS), and their quality was evaluated by sensory evaluation. A total of 144 compounds were structurally identified, belonging to 11 chemical classes including catechins, dimeric catechins, flavonoid glycosides (flavonol-O-glycosides and flavone-C-glycosides), N-ethyl-2-pyrrolidinonesubstituted flavan-3-ols (EPSFs), amino acids, phenolic acids, organic acids, alkaloids, and lipids. Partial least squares discriminant (PLSD) analysis and heatmap analysis showed distinct differences in chemical components among rock tea samples with different baking treatments. A total of 84 compounds that significantly differed among treatment groups were identified (P < 0.05). The contents of most amino acids, epicatechins, dimeric catechins (theaflavins and theasinensins), alkaloids (5’-methionosine and adenosine phosphate), phenolic acids (isochlorogenic acid, strictinin and theogallin), and flavonoid glycosides were gradually decreased with roasting time at 120 ℃, while most lipids (MG(18:3), LysoPC(18:3), and palmitic acid), some flavonol aglycones (myricetin, kaempferol, and quercetin), and some organic acids (pyroglutamic acid and 5-hydroxymethyl-2-furfural) showed the opposite trend. The contents of most EPSF compounds were increased linearly with roasting temperature and time, but it was gradually decreased with baking time at 140 ℃. Sensory evaluation showed that low-temperature long-time (8–10 h at 100 ℃) and medium-temperature short-time (2–4 h at 120 ℃) were beneficial for the quality improvement of rock tea. This study provides a theoretical basis for the quality improvement of Wuyi rock tea.

In this study, the digestion-promoting function of an aqueous extract from Maojian green tea extract (MJ-GTE) was evaluated by small intestinal motility in mice as well as body mass, body mass gain, food intake, food utilization rate, gastric pepsin activity, and gastric pepsin excretion in rats. The chemical composition of MJ-GTE was then systematically analyzed using metabolomics based on ultra-high performance liquid chromatography-quadrupole electrostatic orbitrap mass spectrometry (UPLC-Q-Exactive/MS). The results of animal experiments showed that the intestinal propulsion ratio of ink in the high-dose MJ-GTE group (0.83 g/(kg·d)) was significantly increased compared with the model group (P < 0.05), and gastric pepsin excretion in the medium-dose MJ-GTE group (0.21 g/(kg·d)) was significantly increased compared with the negative control group (deionized water) (P < 0.05), which collectively indicated that MJ-GTE has a digestion-promoting effect. The metabolomics analysis identified 98 compounds, among which, flavones (apigenin and luteolin, 0.14–0.77 mg/g), flavanones (naringenin and eriodictyol, 0.49–1.49 mg/g), flavone-7-O-glycosides (0.57–9.07 mg/g), and flavanone-7-O-glycosides (4.49–38.98 mg/g) were the major components in MJ-GTE. This study will provide a theoretical basis for the promotion and development of Maojian green tea and related products in the future.

In order to investigate the effect of cultivar and processing technique on the chemical composition of tea, this study analyzed green tea, fresh-scent oolong tea, strong-scent oolong tea and black tea made from the fresh leaves of the ‘Tieguanyin’ and ‘Shuixian’ cultivars from the same graphical origin using metabolomics based on ultra-high performance liquid chromatography-time-of-flight mass spectrometry (UPLC-TOF-MS). The results showed that the chemical compositions of tea samples made from different tea cultivars differed considerably. The contents of most lipids, alkaloids and methylated catechins were higher and the contents of theanine, most catechins, flavone (flavonol) glycosides, phenolic acids and N-ethyl-2-pyrrolidinone-substituted flavan-3-ols were lower in ‘Tieguanyin’ tea than in ‘Shuixian’ tea. Processing techniques also significantly impacted the chemical composition of tea. A total of 127 differential compounds wereselected, among which the contents of most catechins, dimeric catechins, alkaloids and some amino acid compounds were significantly higher in green tea than in other kinds of tea. The contents of some amino acids and flavone (flavonol) glycosides (quercetin-3-galactoside, and kaempferol-3-glucosylrutanoside) were higher in fresh-scent oolong tea. The contents of N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF), some flavone (flavonol) glycosides (quercetin-3-glucoside, and kaempferol-3-6”-acetylgalactoside), and lipid compounds in strong-scent oolong tea were higher, while black tea was richer in theaflavins and several flavone (flavonol) glycosides.