Identification of Cu(111) as Superior Active Sites for Electrocatalytic NO Reduction to NH3 with High Single-Pass Conversion Efficiency.

Opting for NO as an N source in electrocatalytic NH3 synthesis presents an intriguing approach to tackle energy and environmental challenges. However, blindly pursuing high NH3 synthesis rates and Faradaic efficiency (FE) while ignoring the NO conversion ratio could result in environmental problems. Herein, Cu nanosheets with exposed (111) surface is fabricated and exhibit a NO-to-NH3 yield rate of 371.89 µmol cm-2 h-1 (flow cell) and the highest FE of 93.19±1.99 % (H-type cell). The NO conversion ratio is increased to the current highest value of 63.74 % combined with the development of the flow cell. Additionally, Crystal Orbital Hamilton Population (COHP) clearly reveals that the "σ-π* acceptance-donation" is the essence of the interaction between the Cu and NO as also supported by operando attenuated total reflection infrared spectroscopy (ATR-IRAS) in observing the key intermediate of NO- . This work not only achieves a milestone NO conversion ratio for electrocatalytic NO-to-NH3 , but also proposes a new descriptor that utilizes orbital hybridization between molecules and metal centers to accurately identify the real active sites of catalysts.

Cell-free DNA methylation markers for differential diagnosis of hepatocellular carcinoma.

BACKGROUND: Aberrant DNA methylation may offer opportunities in revolutionizing cancer screening and diagnosis. We sought to identify a non-invasive DNA methylation-based screening approach using cell-free DNA (cfDNA) for early detection of hepatocellular carcinoma (HCC). METHODS: Differentially, DNA methylation blocks were determined by comparing methylation profiles of biopsy-proven HCC, liver cirrhosis, and normal tissue samples with high throughput DNA bisulfite sequencing. A multi-layer HCC screening model was subsequently constructed based on tissue-derived differentially methylated blocks (DMBs). This model was tested in a cohort consisting of 120 HCC, 92 liver cirrhotic, and 290 healthy plasma samples including 65 hepatitis B surface antigen-seropositive (HBsAg+) samples, independently validated in a cohort consisting of 67 HCC, 111 liver cirrhotic, and 242 healthy plasma samples including 56 HBsAg+ samples. RESULTS: Based on methylation profiling of tissue samples, 2321 DMBs were identified, which were subsequently used to construct a cfDNA-based HCC screening model, achieved a sensitivity of 86% and specificity of 98% in the training cohort and a sensitivity of 84% and specificity of 96% in the independent validation cohort. This model obtained a sensitivity of 76% in 37 early-stage HCC (Barcelona clinical liver cancer [BCLC] stage 0-A) patients. The screening model can effectively discriminate HCC patients from non-HCC controls, including liver cirrhotic patients, asymptomatic HBsAg+ and healthy individuals, achieving an AUC of 0.957(95% CI 0.939-0.975), whereas serum α-fetoprotein (AFP) only achieved an AUC of 0.803 (95% CI 0.758-0.847). Besides detecting patients with early-stage HCC from non-HCC controls, this model showed high capacity for distinguishing early-stage HCC from a high risk population (AUC=0.934; 95% CI 0.905-0.963), also significantly outperforming AFP. Furthermore, our model also showed superior performance in distinguishing HCC with normal AFP (< 20ng ml-1) from high risk population (AUC=0.93; 95% CI 0.892-0.969). CONCLUSIONS: We have developed a sensitive blood-based non-invasive HCC screening model which can effectively distinguish early-stage HCC patients from high risk population and demonstrated its performance through an independent validation cohort. TRIAL REGISTRATION: The study was approved by the ethic committee of The Second Xiangya Hospital of Central South University (KYLL2018072) and Chongqing University Cancer Hospital (2019167). The study is registered at ClinicalTrials.gov(# NCT04383353 ).

Measuring demand and supply of community care services for older people healthy ageing in rural Zhejiang Province.

BACKGROUND: A consequence of demographic trends and economic prosperous is the increasing diversity in needs for care services. However, the traditional family support for older people has been largely supplanted by the wider provision of community care services. This study aims to investigate the current status of demand and supply in community care services across different villages of Zhejiang province and assess service effectiveness for healthy ageing. METHODS: A questionnaire survey was carried out towards 207 rural villages across 9 cities in Zhejiang province. One hundred eighty-six valid responses were received, representing a response rate of around 89.9%. Descriptive statistics were employed to identify older villagers' care needs and available community services. Comparative analysis examined the balance between the demand and supply of community care services. Correlation analysis were applied to determine key factors that impacted the supply of social services in rural communities. RESULTS: The research found that rural older residents normally lived with their children or spouse with limited literacy and income. On average the categories of community care services is substantially small in comparison with the increasingly diverse demands of older people in rural areas. There was an obvious mismatch between service demand and service supply in rural communities, which often caused the waste of public resources. Moving forward, the uppermost priority is given to infrastructure construction service and daily life service, while little attention is paid to mental health service and specialized nursing service. CONCLUSION: There needs to be an improvement in the socio-economic capacity of rural communities and in the diversity of social care services. Policies and strategies are also needed to encourage private sectors' involvement in providing care services for rural older people. Local government should have a clear vision of the potential demands for community care services, practical guidelines will be useful in guaranteeing better service quality.

The impact of family doctor system on patients' utilisation of general practitioner in primary care facilities-Evidence from Hangzhou, China.

OBJECTIVE: This study aims to examine whether participating in the contracted family doctor system increases patients' utilisation of primary care general practitioner for multiple disease outcomes in China. METHODS: Binary logistic regression models were estimated using data collected from 372 community residents in nine selected districts of Hangzhou, China. RESULTS: Findings revealed that (1) for patients with influenza, diabetes, upper respiratory infection, and gingivitis, those who participated in the contracted family doctor system were approximately 4.3 times, 98.4%, 92.5%, and 52.8% more likely to choose primary care general practitioners (GP) for their initial diagnosis, respectively, as compared with their counterparts who did not have contracted family doctors; (2) For patients with stroke or cerebrovascular disease and cholecystitis or cholelithiasis, those who had contracted family doctors were 1.111 times and 80.6% more likely to choose primary care GP for their subsequent disease maintenance, respectively, as compared to their counterparts without contracted family doctors. CONCLUSION: Our findings indicate that the contracted family doctor system not only increases the utilisation of primary care GP for patients with many chronic conditions but also promotes the overall completion of China's hierarchical medical system in the long run. Policy implications were provided to help policymakers actively construct and develop the contracted family doctor system to promote the hierarchical medical system in China.

Isolation of N-Ethyl-2-pyrrolidinone-Substituted Flavanols from White Tea Using Centrifugal Countercurrent Chromatography Off-Line ESI-MS Profiling and Semi-Preparative Liquid Chromatography.

N-Ethyl-2-pyrrolidinone-substituted flavanols (EPSF) are marker compounds for long-term stored white teas. However, due to their low contents and diasteromeric configuration, EPSF compounds are challenging to isolate. In this study, two representative epimeric EPSF compounds, 5'''R- and 5'''S-epigallocatechin gallate-8-C N-ethyl-2-pyrrolidinone (R-EGCG-cThea and S-EGCG-cThea), were isolated from white tea using centrifugal partition chromatography (CPC). Two different biphasic solvent systems composed of 1. N-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v/v/v) and 2. N-hexane-ethyl acetate-acetonitrile-water (0.7:3.0:1.3:5.0, v/v/v/v) were used for independent pre-fractionation experiments; 500 mg in each separation of white tea ethyl acetate partition were fractionated. The suitability of the two solvent systems was pre-evaluated by electrospray mass-spectrometry (ESI-MS/MS) analysis for metabolite distribution and compared to the results of the CPC experimental data using specific metabolite partition ratio KD values, selectivity factors α, and resolution factors RS. After size-exclusion and semi-preparative reversed-phase liquid chromatography, 6.4 mg of R-EGCG-cThea and 2.9 mg of S-EGCG-cThea were recovered with purities over 95%. Further bioactivity evaluation showed that R- and S-EGCG-cThea possessed in vitro inhibition effects on α-glucosidase with IC50 of 70.3 and 161.7 µM, respectively.

Is China facing the social risks associated with reliance on hospitalization for the care of the elderly with chronic diseases?

This study aims to investigate if China is facing the social risks associated with reliance on hospitalization for the care of the elderly with chronic diseases. Textual studies and big data analysis indicate the following outcomes: (1) The elderly population suffering from chronic diseases is expanding rapidly, while the prevalence rate also shows a growing trend; (2) the reliance on hospitalization for the care of the elderly patients exists and has caused three new social risks; and (3) these social risks are wasted health resources, poverty between individuals and families, and relative increase in the disability rate of the elderly after hospital admission. We conclude that effectively defusing the risks entails strengthening the management of chronic diseases related to communal public health, initiating the concept of "continuity of care" to pursue an active combination of medical and health care, hastening the implementation of long-term care insurance (LTCI) and other policy measures.

Metabolomic analysis reveals the composition differences in 13 Chinese tea cultivars of different manufacturing suitabilities.

BACKGROUND: Green tea and black tea are manufactured using appropriate tea cultivars in China. However, the metabolite differences relating to the manufacturing suitability of tea cultivars are unclear. In the present study, we performed a non-targeted metabolomic analysis on 13 Chinese tea cultivars using ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry to investigate comprehensively the metabolite differences between cultivars suitable for manufacturing green tea (GT cultivars) and cultivars suitable for manufacturing both green tea and black tea (G&BT cultivars). RESULTS: Multivariate statistical analysis and cluster analysis divided the 13 cultivars into two groups, namely GT cultivars and G&BT cultivars, which correlated with their manufacturing suitability. The GT cultivars contained higher levels of flavonoid glycosides, whereas the G&BT cultivars contained higher levels of catechins, dimeric catechins, phenolic acids and alkaloids. CONCLUSION: Metabolic pathway analysis revealed that the flavonoid pathway inclined toward the synthesis of flavonoid glycosides in GT cultivars, whereas it inclined toward the synthesis of catechins and phenolic acids in G&BT cultivars. The results of the present study will be helpful for discriminating the manufacturing suitability of tea cultivars and investigating their breeding. © 2017 Society of Chemical Industry.

[Efficiency of isolated caudate lobe resection for huge hepatocellular carcinoma (10 cm or larger in diameter)].

OBJECTIVE: To explore the feasibility and efficacy of isolated caudate lobe resection for caudate lobe in huge hepatocellular carcinoma(10 cm or larger in diameter).
 Methods: Clinical data of 27 patients with hepatocellular carcinoma larger than 10 cm who underwent isolated caudate lobe resection from January 2001 to December 2011 were retrospectively analyzed.
 Results: All the patients successfully completed the operation. There was no postoperative death. Median operative time was 288 min, and the estimated intraoperative blood loss was 2 260 mL. Postoperative morbidity rate was 44.4%. The patients were discharged successfully after active treatment. Overall survival rates at 1, 3, and 5 years were 80.2%, 52.1%, and 27.1%, respectively.
 Conclusion: Isolated caudate lobe resection is safe and effective for caudate lobe huge hepatocellular carcinoma.

Multiple reaction monitoring-ion pair finder: a systematic approach to transform nontargeted mode to pseudotargeted mode for metabolomics study based on liquid chromatography-mass spectrometry.

Pseudotargeted metabolic profiling is a novel strategy combining the advantages of both targeted and untargeted methods. The strategy obtains metabolites and their product ions from quadrupole time-of-flight (Q-TOF) MS by information-dependent acquisition (IDA) and then picks targeted ion pairs and measures them on a triple-quadrupole MS by multiple reaction monitoring (MRM). The picking of ion pairs from thousands of candidates is the most time-consuming step of the pseudotargeted strategy. Herein, a systematic and automated approach and software (MRM-Ion Pair Finder) were developed to acquire characteristic MRM ion pairs by precursor ions alignment, MS(2) spectrum extraction and reduction, characteristic product ion selection, and ion fusion. To test the reliability of the approach, a mixture of 15 metabolite standards was first analyzed; the representative ion pairs were correctly picked out. Then, pooled serum samples were further studied, and the results were confirmed by the manual selection. Finally, a comparison with a commercial peak alignment software was performed, and a good characteristic ion coverage of metabolites was obtained. As a proof of concept, the proposed approach was applied to a metabolomics study of liver cancer; 854 metabolite ion pairs were defined in the positive ion mode from serum. Our approach provides a high throughput method which is reliable to acquire MRM ion pairs for pseudotargeted metabolomics with improved metabolite coverage and facilitate more reliable biomarkers discoveries.

Ion fusion of high-resolution LC-MS-based metabolomics data to discover more reliable biomarkers.

A systematic approach for the fusion of associated ions from a common molecule was developed to generate "one feature for one peak" metabolomics data. This approach guarantees that each molecule is equally selected as a potential biomarker and may largely enhance the chance to obtain reliable findings without employing redundant ion information. The ion fusion is based on low mass variation in contrast to the theoretical calculation measured by a high-resolution mass spectrometer, such as LTQ orbitrap, and a high correlation of ion pairs from the same molecule. The mass characteristics of isotopic distribution, neutral loss, and adduct ions were simultaneously applied to inspect each extracted ion in the range of a predefined retention time window. The correlation coefficient was computed with the corresponding intensities of each ion pair among all experimental samples. Serum metabolomics data for the investigation of hepatocellular carcinoma (HCC) and healthy controls were utilized as an example to demonstrate this strategy. In total, 609 and 1084 ion pairs were respectively found meeting one or more criteria for fusion, and therefore fused to 106 and 169 metabolite features of the datasets in the positive and negative modes, respectively. The important metabolite features were separately discovered and compared to distinguish the HCC from the healthy controls using the two datasets with and without ion fusion. The results show that the developed method can be an effective tool to process high-resolution mass spectrometry data in "omics" studies.

Nontargeted modification-specific metabolomics study based on liquid chromatography-high-resolution mass spectrometry.

Modifications of genes and proteins have been extensively studied in systems biology using comprehensive analytical strategies. Although metabolites are frequently modified, these modifications have not been studied using -omics approaches. Here a general strategy for the nontargeted profiling of modified metabolites, which we call "nontargeted modification-specific metabolomics", is reported. A key aspect of this strategy was the combination of in-source collision-induced dissociation liquid chromatography-mass spectrometry (LC-MS) and global nontargeted LC-MS-based metabolomics. Characteristic neutral loss fragments that are specific for acetylation, sulfation, glucuronidation, glucosidation, or ribose conjugation were reproducibly detected using human urine as a model specimen for method development. The practical application of this method was demonstrated by profiling urine samples from liver cirrhosis patients. Approximately 900 features were identified as modified endogenous metabolites and xenobiotics. Moreover, this strategy supports the identification of compounds not included in traditional metabolomics databases (HMDB, Metlin, and KEGG), which are currently referred to as "unknowns" in metabolomics projects. Nontargeted modification-specific metabolomics opens a new perspective in systems biology.

Study of urinary steroid hormone disorders: difference between hepatocellular carcinoma in early stage and cirrhosis.

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world. Discovery of novel biomarkers for early HCC from other liver diseases such as cirrhosis is of great clinical benefit. In this study, a novel steroid hormone metabolomic method based on liquid chromatography-mass spectrometry combined with logistic regression analysis was applied to study the steroid hormone disorders and to screen potential urinary steroid hormone biomarkers of early HCC. Thirty-six urinary steroid hormones were detected and quantified in healthy controls, cirrhotic patients, and early HCC patients. Heat map analysis and multivariate statistical analysis suggested severe disorders of steroid hormone network and holistically decreased urinary steroid hormone pattern in cirrhotic and early HCC patients. Logistic regression analysis reveals that a panel of two urinary steroid hormones (epitestosterone and allotetrahydrocortisol) displayed excellent diagnostic capability for distinguishing early HCC from cirrhosis with area under the curve (AUC) = 0.938 of receiver operating characteristic (ROC) analysis. These results help to overcome the disadvantage of lower sensitivity and specificity of alpha-fetoprotein for distinguishing early HCC from cirrhosis. Our work shows that steroid hormone metabolomics is a promising biomarker tool for biomarker study of early HCC.

[Application of liver hanging maneuver in anterior approach for isolated complete liver caudate lobectomy].

OBJECTIVE: To explore the technique and effect of liver hanging maneuver in anterior approach for isolated complete liver caudate lobectomy. METHODS: We recruited 17 patients with liver caudate lobe tumor (13 primary hepatocellular carcinoma, 3 cholangiocarcinoma and 1 liver metastasis from colorectal cancer). Isolated complete caudate lobectomy with liver hanging maneuver was performed in 17 patients. RESULTS: All 17 patients were successfully received the above-mentioned operation. The operative time was 166-427 (211.5 ± 20.1) min and the intraoperative blood loss was 372-1 208 (472.7 ± 83.6) mL. There was no operative death. The survival rates of follow up for 1, 3 and 5 years were 76.5%, 52.9% and 23.5%, respectively. CONCLUSION: Liver hanging maneuver for isolated complete resection of the caudate lobe is an ideal approach for liver neoplasms resection.

Multifactorial risk prediction analysis of liver metastasis in colorectal cancer: incorporating programmed cell death ligand 1 combined positive score and other factors.

BACKGROUND: The occurrence of liver metastasis significantly affects the prognosis of colorectal cancer (CRC). Existing research indicates that primary tumor location, vascular invasion, lymph node metastasis, and abnormal preoperative tumor markers are risk factors for CRC liver metastasis. Positive expression of programmed cell death ligand 1 (PD-L1) may serve as a favorable prognostic marker for nasopharyngeal and gastric cancers, in which combined positive score (CPS) quantifies the level of PD-L1 expression. This study aimed to explore CPS as a potential risk factor for CRC liver metastasis and integrate other independent risk factors to establish a novel predictive model for CRC liver metastasis. METHODS: A retrospective analysis was conducted on 437 patients with CRC pathologically diagnosed at The Second Xiangya Hospital of Central South University from January 1, 2019, to December 31, 2021. Data were collected, including CPS, age, gender (male and female), primary tumor location, Ki-67 expression, pathologic differentiation, neural invasion, vascular invasion, lymph node metastasis, and preoperative tumor markers. The optimal cutoff point for the continuous variable CPS was determined using the Youden index, and all CPSs were dichotomized into high- and low-risk groups based on this threshold (scores below the threshold were considered high risk, and score above the threshold were considered low risk). Univariate logistic regression analysis was employed to identify risk factors for CRC liver metastasis, followed by multivariate logistic regression analysis to integrate the selected risk factors. The predictive model was validated through the construction of receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA). A nomogram was constructed for visualization. RESULTS: The determined cutoff point for PD-L1 CPS was 4.5, with scores below this threshold indicating a high risk of CRC liver metastasis. In addition, primary tumor origin other than the rectum, presence of pericolonic lymph node metastasis, and abnormal levels of tumor markers carcinoembryonic antigen and cancer antigen 19-9 were identified as independent risk factors for CRC liver metastasis. The constructed clinical prediction model demonstrated good predictive ability and accuracy, with an area under the ROC curve of 0.871 (95% CI, 0.838-0.904). CONCLUSION: The exploration and validation of CPS as a novel predictor of CRC liver metastasis were performed. Based on these findings, a new clinical prediction model for CRC liver metastasis was developed by integrating other independent risk factors. The DCA, clinical impact curve, and nomogram graph constructed on the basis of this model have significant clinical implications and guide clinical practice.

Dynamic Hydroxylation Enhances Hydrogen Atom Abstraction from Water for Nitrogen Fixation Revealed by Isotope Labeling in Situ Fourier-Transform Infrared Spectroscopy.

Employing water as a hydrogen source to participate in the hydrogen atom transfer (HAT) process is a low-cost and carbon-free process demonstrating great economic and environmental potential in catalysis. However, the low efficiency of hydrogen atom abstraction from water leads to slow kinetics of HAT for most hydrogenative reactions. Here, we prepared ultrathin Bi4O5Cl2 nanosheets where the surface can be in situ reconstructed via hydroxylation under light illumination to facilitate the abstraction of hydrogen atoms from pure water for efficient nitrogen fixation. Consequently, the isotope labeling in situ Fourier-transform infrared spectroscopy (FT-IR) involving H2O and D2O has clearly revealed that the hydroxyl groups tend to be adsorbed on the chloride vacancy sites on the Bi4O5Cl2 surface to form hydroxylated surfaces, where the hydroxylated photocatalyst surface enables partial dehydrogenation of water into H2O2, allowing the utilization of H atoms for efficient of N2 hydrogenation via HAT steps. This work elucidates the in-depth reaction mechanism of hydrogen atom extraction from H2O molecules via the light-generated chloride vacancy to promote photocatalytic nitrogen fixation, ultimately enabling the inspiration and providing crucial rules for the design of important functional materials that can efficiently deliver active hydrogen for chemical synthesis.

Lattice Strain in High Entropy Oxides Promote CO2 Photomethanation.

Lattice strain is widely investigated to improve the performance of heterogeneous catalysts, however, the effect of lattice strain is under-explored in high-entropy oxide based photocatalyst. In this study, noble-metal-free (CoCrMnFeNi)Ox with lattice strain is synthesized using a temperature-controlled, template-free and salt-assisted strategy. In the presence of lattice strain, an intensive internal electric field is formed in (CoCrMnFeNi)Ox, promoting the separation of photoinduced charge carriers. The size of the (CoCrMnFeNi)Ox can be tuned by varying the calcination temperature. Specifically, (CoCrMnFeNi)Ox prepared at a higher temperature possesses a smaller grain size exposing more active sites, resulting in an enhanced CO2 photomethanation performance. This work provides valuable insights for the rational design of the photocatalysts and highlights the promising role of high-entropy oxides in heterogeneous photocatalysis.

Investigations of the highly efficient processing technique, chemical constituents, and anti-inflammatory effect of N-ethyl-2-pyrrolidinone-substituted flavan-3-ol (EPSF)-enriched white tea.

N-Ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) are a newly discovered compound class in tea with various bioactivities. This study aimed to develop a novel processing technique to enhance EPSF contents in white tea efficiently. Using optimal processing parameters of 125 °C and 30 min in a high-temperature sterilizing oven, total EPSF content significantly increased by 1.42-18.80-fold to 1.57-6.22 mg/g without impacting sensory characteristics. Metabolomics analysis revealed elevated levels of nucleosides, nucleotides, bases, theaflavins, flavonol aglycones, EPSFs, and most flavone-C-glycosides, as well as decreased levels of amino acids, procyanidins, theasinensins, several flavanols, and flavonol-O-glycosides after EPSF-enrichment treatment. Furthermore, the EPSF-enriched white tea exhibited notable anti-inflammatory effects, mitigating xylene-induced ear edema in mice and carrageenan-induced paw edema and cotton ball-induced granulomas in rats. This study developed a new processing technique for highly efficient enhancement of EPSFs in white tea and demonstrated that EPSF-enriched white tea has a potential to serve as effective anti-inflammatory dietary supplement.

Stored white tea ameliorates DSS-induced ulcerative colitis in mice by modulating the composition of the gut microbiota and intestinal metabolites.

Changes in the chemical composition of white tea during storage have been studied extensively; however, whether such chemical changes impact the efficacy of white tea in ameliorating colitis remains unclear. In this study, we compared the effects of new (2021 WP) and 10-year-old (2011 WP) white tea on 3% dextrose sodium sulfate (DSS)-induced ulcerative colitis in mice by gavaging mice with the extracts at 200 mg kg-1 day-1. Chemical composition analysis showed that the levels of 50 compounds, such as flavanols, dimeric catechins, and amino acids, were significantly lower in the 2011 WP extract than in the 2021 WP extract, whereas the contents of 21 compounds, such as N-ethyl-2-pyrrolidinone-substituted flavan-3-ols, theobromine, and (-)-epigallocatechin-3-(3''-O-methyl) gallate, were significantly higher. Results of the animal experiments showed that 2011 WP ameliorated the pathological symptoms of colitis, which was superior to the activity of 2021 WP, and this effect was likely enhanced based on the decreasing of the relative abundance of the g_bacteroides and g_Escherichia-Shigella flora in mice with colitis and promoting the conversion of primary bile acids to secondary bile acids in the colon. These results will facilitate the development of novel functional products from white tea.

Metabolomics investigation of the chemical variations in white teas with different producing areas and storage durations.

In this study, we employed nontargeted metabolomics and quantitative analysis to explore the variations in metabolites among white teas from different production areas and with varying storage durations. A total of 83 compounds exhibited differential levels between Zhenghe and Fuding white tea, 89 between Zhenghe and Jinggu, and 75 between Fuding and Jinggu white tea. Concerning the storage of white tea, the concentrations of flavanols, dimeric catechins, and amino acids decreased over time, while N-ethyl-2-pyrrolidone-substituted flavanols (EPSFs), caffeine, adenosine monophosphate (AMP), and adenosine increased. Galloylated flavanols showed a higher propensity to form EPSFs with theanine compared to nongalloylated flavanols during storage. Theanine and epigallocatechin gallate were more inclined to generate S-configuration EPSFs during storage in Fuding and Jinggu white tea samples, while R-configuration EPSFs were more readily formed in Zhenghe white tea samples. This study offers a comprehensive understanding of the changes in metabolites during the storage of white tea.

Unraveling the Enantiomeric Distribution of Glycosidically Bound Linalool in Teas (Camellia sinensis) and Their Acidolysis Characteristics and Pyrolysis Mechanism.

Glycosidically bound linalool plays important roles in the formation of excellent tea flavor, while their enantiomeric distribution in teas and the actual transformations with free linalool are still unclear. In this study, a novel chiral ultrahigh performance liquid chromatography-mass spectrometry/mass spectrometry approach to directly analyze linalyl-ß-primeveroside and linalyl-ß-d-glucopyranoside enantiomers in teas was established and then applied in 30 tea samples. A close transformation relationship existed between the two states of linalool for their consistent dominant configurations (most S-form) and corresponding distribution trend in most teas (r up to 0.81). The acidolysis characterization indicated that free linalool might be slowly released from linalyl-ß-primeveroside with stable enantiomeric ratios during long-term withering of white tea in a weakly acidic environment, along with other isomerized products, e.g., geraniol, nerol, α-terpineol, etc. Furthermore, a novel online thermal desorption-gas chromatography-mass spectrometry approach was established to simulate the pyrolysis releasing of linalyl-ß-primeveroside during tea processing. Interestingly, free linalool was not the selected pyrolysis product of linalyl-ß-primeveroside but rather trans/cis-2,6-dimethyl-2,6-octadiene during the high-fire roasting or baking step of oolong and green teas. The identification of above high-fire chemical marks presented great potential to scientifically evaluate the proper thermal conditions in the practical production of tea.