Chemical profiling and discrimination of green tea and Pu-erh raw tea based on UPLC–Q–Orbitrap–MS/MS and chemometrics

Identifying key contributors to the sweet aftertaste of raw Pu-erh tea through analytical and sensory methods

In this study, the key components contributing to raw Pu-erh tea (RAPT) sweet aftertaste were identified. Six RAPTs were investigated through sensory evaluation, mass spectrometry, and taste addition experiments, and 96 taste components of tea infusion were annotated and analyzed. Saliva analysis after drinking tea revealed that 27 components present in tea remained in the mouth. On the basis of the results of the multivariate statistical analyses, we hypothesized that alkaloids and flavonoids might influence the sweet aftertaste strength of RAPT. Finally, the results of the taste addition experiments revealed that theophylline and rutin are key components that significantly influence the sweet aftertaste intensity of the RAPT. This strategy can be used as a methodology for analyzing the taste of tea, and the results can provide an evaluation index for evaluating the quality of RAPT.

Resource utilization of tea waste in biochar and other areas: Current status, challenges and future prospects

The consumption of tea, one of the most popular non-alcoholic beverages, has steadily increased, leading to a significant rise in global tea production and consequently the generation of substantial amounts of tea waste annually. China alone generates more than 5 million tons of tea waste annually, comprising trimmed stems, discarded leaves and buds, waste from the manufacturing process, and residue after brewing. Tea is rich in polyphenols, polysaccharides, amino acids, alkaloids, and other active substances. Leveraging substantial quantities of tea waste can produce cost-effective derivatives across various sectors, thereby enhancing its utilitarian value and promoting a circular economy, for "Waste to Treasure". This study aims to evaluate the potential for resourceful utilization of tea waste in diverse applications. The current state of research concerning various applications of tea waste, including its use in biochar, composting feedstock, sludge performance modifiers, disinfection and biocides, as well as animal feed is comprehensively summarized. Focusing on the preparation and application of tea-waste-derived biochar (TWB), this study identifies several limitations in current TWB production technologies, including challenges related to performance, yield, and economic viability. Combined with bibliometric analysis, machine learning methods have emerged as valuable tools for evaluating and predicting biochar performance, as well as optimizing the biochar production process. An economic assessment of TWB production costs revealed that its production cost ($434.2/ton) is lower than that of corn stover ($454.19/ton) and wheat straw ($448.01/ton), but higher than rice straw ($425.73/ton). Furthermore, the analysis highlighted pyrolysis time and heating rate as critical factors influencing production costs, offering new insights compared to prior studies. This paper summarizes the progress and challenges faced by tea wastes in the field of biochar and looks at future directions. Results will provide sustainable utilization of tea waste and assist in exploiting this abundant and cheap waste biomass in many ways.

Predicting Precursor Ions Combined with Fragmentation Pathway for Screening and Identification of Flavan-3-ol Oligomers in Tea (Camellia sinensis. var. assamica)

Flavan-3-ol oligomers (FLOs), including proanthocyanidins (PAs) and theasinensins (TSs), contribute greatly to the flavor and bioactivity of the tea beverage. Ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry has been widely used in profiling a wide range of compounds in tea. However, the detection and identification of FLOs with low concentration and high structural diversity remain meaningful yet challenging work. Herein, we propose a strategy that enables efficient discovery and annotation of FLOs, especially those with a relatively high degree of polymerization (DP, ≥3). Based on the known monomers and the specific polymerization pattern between them, the strategy predicted a theoretical list of precursor ions of FLO. Matching the predicted list against the experimental ion features screened out 490 features as the candidate of FLOs from over 10 000 raw features. Investigation of the fragmentation pathways of 17 known FLOs found that both PAs and TSs are easily subjected to RDA cleavage, which produced a series of characteristic fragmentation ions and neutral losses. Moreover, successive cleavage of the C4 → C8 bond between monomer units is observed for PAs, leading to the generation of characteristic fragmentation ions corresponding to monomeric flavan-3-ols. Assisted by the characteristic fragmentation pathways, 52 FLOs (DP: 2-6) were finally annotated from the 490 retained features. Their chemical structures were verified by depolymerization experiments using menthofuran as the nucleophilic trapping reagent. Among them, the pentamers and hexamers were detected in a Yunnan large leaf tea for the first time. Semiquantitation and multivariate statistical analysis indicate that PAs exhibit higher contents in green tea, and TSs show higher levels in black and white tea.

An algorithm-driven intelligent mining and identification strategy for natural product mass spectrometry

Efficiently mining and identification of new compounds from the extensive MS/MS datasets of plant extracts poses a significant challenge due to the structural diversity and compositional complexity inherent in natural products (NPs). Various data post-processing techniques have been developed to simplify the interpretation of MS/MS data; however, they often suffer from limited specificity and precision. Meanwhile, structure annotation following data post-processing is particularly time-consuming. In this study, we introduced an innovative strategy named MS-SMART, which integrates three intelligent algorithms: automatic mining of diagnostic ions, rapid filtration of alkaloids from untargeted MS/MS data, and structural recommendations for filtered components. The feasibility of this approach for rapidly discovering novel compounds was demonstrated using berberine-type alkaloids as an example. Firstly, diagnostic ions were automatically extracted and validated using available reference data. Subsequently, berberine-type compounds were filtered from raw MS/MS data. Finally, the structures of the target components were recommended using building blocks derived from berberines reported in various plants. A total of 103, 198, 60, 80 and 51 berberines were efficiently identified in diverse families and genera, including Stephaniae Epigaeae Radix, Coptidis Rhizoma, Phellodendri Chinensis Cortex, Phellodendri Amurensis Cortex and Corydalis Decumbentis Rhizoma, with 99, 169, 50, 64 and 40 new compounds identified, respectively. Among these, 8, 14, 8, 7 and 12 berberines were confirmed by reference compounds. This strategy provides a new research paradigm for the rapid discovery and identification of different types of new compounds in complex samples.

Effects of Protein on Green Tea Quality in a Milk-Tea Model during Heat Treatment: Antioxidant Activity, Foaming Properties, and Unbound Small-molecule Metabolome

Tea drinks/beverage has a long history and milk is often added to enhance its taste and nutritional value, whereas the interaction between the tea bioactive compounds with proteins has not been systematically investigated. In this study, a milk-tea model was prepared by mixing green tea solution with milk and then heated at 100°C for 15 min. The milk tea was then measured using biochemical assay, antioxidant detection kit, microscopy as well as HPLC-QTOF-MS/MS after ultrafiltration. The study found that as the concentration of milk protein increased in the milk-tea system, the total phenol-protein binding rate raised from 19.63% to 51.08%, which led to a decrease in free polyphenol content. This decrease of polyphenol was also revealed in the antioxidant capacity, including 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability and ferric ion reducing antioxidant power, in a dose-dependent manner. Untargeted metabolomics results revealed that the majority of small-molecule compounds/polyphenols in tea, such as epigallocatechin gallate, (-)-epicatechin gallate, and Catechin 5,7,-di-O-gallate, bound to milk proteins and were removed by ultrafiltration after addition of milk and heat treatment. The SDS-PAGE and Native-PAGE results further indicated that small molecule compounds in tea formed covalent and non-covalent complexes by binding to milk proteins. All above results partially explained that milk proteins form conjugates with tea small-molecule compounds. Consistently, the particle size of the tea-milk system increased as the tea concentration increased, but the polymer dispersity index decreased, indicating a more uniform molecular weight distribution of the particles in the system. Addition of milk protein enhanced foam ability in the milk-tea system but reduced foam stability. In summary, our findings suggest that the proportion of milk added to tea infusion needs to be considered to maintain the quality of milk-tea from multiple perspectives, including stability, nutritional quality and antioxidant activity.

Bioactive components and mechanisms of Pu-erh tea in improving levodopa metabolism in rats through COMT inhibition

Catechol-O-methyltransferase (COMT) plays a central role in the metabolic inactivation of endogenous neurotransmitters and xenobiotic drugs and hormones having catecholic structures. Its inhibitors are used in clinical practice to treat Parkinson's disease. In this study, a fluorescence-based visualization inhibitor screening method was developed to assess the inhibition activity on COMT both in vitro and in living cells. Following the screening of 94 natural products, Pu-erh tea extract exhibited the most potent inhibitory effect on COMT with an IC50 value of 0.34 μg mL-1. In vivo experiments revealed that Pu-erh tea extract substantially hindered COMT-mediated levodopa metabolism in rats, resulting in a significant increase in levodopa levels and a notable decrease in 3-O-methyldopa in plasma. Subsequently, the chemical components of Pu-erh tea were analyzed using UHPLC-Q-Exactive Orbitrap HRMS, identifying 24 major components. Among them, epigallocatechin gallate, gallocatechin gallate, epicatechin gallate, and catechin gallate exhibited potent inhibition of COMT activity with IC50 values from 93.7 nM to 125.8 nM and were the main bioactive constituents in Pu-erh tea responsible for its COMT inhibition effect. Inhibition kinetics analyses and docking simulations revealed that these compounds competitively inhibit COMT-mediated O-methylation at the catechol site. Overall, this study not only explained how Pu-erh tea catechins inhibit COMT, suggesting Pu-erh tea as a potential dietary intervention for Parkinson's disease, but also introduced a new strategy for discovering COMT inhibitors more effectively.

A sensor array based on a nanozyme with polyphenol oxidase activity for the identification of tea polyphenols and Chinese green tea

Green tea is popular among consumers because of its high nutritional value and unique flavor. There is often a strong correlation among the type of tea, its quality level and the price. Therefore, the rapid identification of tea types and the judgment of tea quality grades are particularly important. In this work, a novel sensor array based on nanozyme with polyphenol oxidase (PPO) activity is proposed for the identification of tea polyphenols (TPs) and Chinese green tea. The absorption spectra changes of the nanozyme and its substrate in the presence of different TPs were first investigated. The feature spectra were scientifically selected using genetic algorithm (GA), and then a sensor array with 15 sensing units (5 wavelengths × 3 time) was constructed. Combined with the support vector machine (SVM) discriminative model, the discriminative rate of this sensor array was 100% for different concentrations of typical TPs in Chinese green tea with a detection limit of 5 μM. In addition, the identification of different concentrations of the same tea polyphenols and mixed tea polyphenols have also been achieved. Based on the above study, we further developed a facile and efficient new method for the category differentiation and adulteration identification of green tea, and the accuracy of this array was 96.88% and 100% for eight types of green teas and different adulteration ratios of Biluochun, respectively. This work has significance for the rapid discrimination of green tea brands and adulteration.

Rapid analysis of insecticidal metabolites from the entomopathogenic fungus Beauveria bassiana 331R using UPLC-Q-Orbitrap MS

Beauveria bassiana, a representative entomopathogenic fungus, is increasingly being utilized as an eco-friendly pest management alternative to chemical insecticides. This fungus produces a range of insecticidal secondary metabolites that act as antimicrobial and immunosuppressive agents. However, detailed qualitative and quantitative analysis related to these compounds remains scarce, we developed a method for the rapid analysis of these metabolites. Eight secondary metabolites (bassianin, bassianolide, beauvericin, beauveriolide I, enniatin A, A1, and B, and tenellin) were efficiently extracted when B. bassiana-infected Tenebrio molitor larvae were ground in 70% EtOH extraction solvent and subsequently subjected to ultrasonic treatment for 30 min. The eight metabolites were rapidly and simultaneously analyzed using ultra-performance liquid chromatography-quadrupole-Orbitrap mass spectrometry (UPLC-Q-Orbitrap MS). Bassianolide (20.6-51.1 µg/g) and beauvericin (63.6-109.8 µg/g) were identified as the main metabolites in B. basssiana-infected larvae, indicating that they are likely major toxins of B. bassiana. Validation of the method exhibited recovery rates in the range of 80-115% and precision in the range of 0.1-8.0%, indicating no significant interference from compounds in the matrix. We developed a method to rapidly analyze eight insecticidal metabolites using UPLC-Q-Orbitrap MS. This can be extensively utilized for detecting and producing insecticidal fungal secondary metabolites.

Quantitative analysis and survey of 9,10-anthraquinone contaminant in Chinese Liupao tea

Recently, 9,10-anthraquinone (AQ) contamination in Chinese Liupao tea has attracted much attention because the tea for export must meet the EU limit (10 µg kg^-1). In this study, a method was developed in which the sample was extracted with n-hexane-acetone solution, then purified with Florisil adsorbent, detected by GC-MS/MS and contamination levels of AQ determined using an internal standard. This method was found to be more suitable for Liupao tea and other dark tea complex substrates than the QuEChERS procedure. The sample pre-treatment method was optimized with respect to extraction reagent and clean-up column adsorbent and n-hexane-acetone selected as the optimal extraction solvent. When the content of Florisil in the column was 1.0 g, the optimum clean-up was achieved. The new method reduced the limit of quantification (LOQ) of AQ to 10 μg kg^-1, and accuracy was also further improved. The recovery of AQ-fortified tea samples containing 20-100 µg·kg^-1 was 94.5-100.4%, and the relative standard deviation (RSD) was less than 1.3%. In a small survey, 98 Liupao tea samples on the market were tested by the new method. It was found that 61 samples were positive (occurrence rate 63.3%), and thus exceeded the EU limit (10 µg kg^-1). This study also found that the contamination of AQ in Liupao tea increased with the length of ageing. The source of AQ in the Liupao tea ageing process will be the focus of further research.

Flavor perception and health benefits of tea

As one of the most consumed non-alcoholic beverages in the world, tea is acclaimed for its pleasant flavor and various health benefits. Different types of tea present a distinctive flavor and bioactivity due to the changes in the composition and proportion of respective compounds. This article aimed to provide a more comprehensive understanding of tea flavor (including aroma and taste) and the character of tea in preventing and alleviating diseases. The recent advanced modern analytical techniques for revealing flavor components in tea, including enrichment, identification, quantitation, statistics, and sensory evaluation methodologies, were summarized in the following content. Besides, the role of tea in anti-cancer, preventing cardiovascular disease and metabolic syndrome, anti-aging and neuroprotection, and regulating gut microbiota was also listed in this article. Moreover, questions and outlooks were mentioned to objectify tea products' flavor quality and health benefits on a molecular level and significantly promote our understanding of the comprehensive value of tea as a satisfactory health beverage in the future.

Rapid screening and characterization of 2-(2-phenylethyl)chromones in agarwood by UHPLC-Q-Exactive Orbitrap-MS

The purpose of this study is to develop an improved comprehensive data filtering strategy, which was implemented primarily through the Microsoft Office platform's Excel software for rapid screening of potential 2-(2-phenylethyl)chromone (PEC) monomers and their dimers (PEC dimers) obtained from agarwood. A total of 108 PEC monomers and 30 PEC dimers in agarwood were characterized. In conclusion, the results obtained in this work could provide useful information for the future utilization of agarwood. In particular, it is the first time to conduct an in-depth analysis of the MS/MS fragmentation behavior of a large number of PEC monomers and PEC dimers, including the identification of substituent positions of them. The proposed data filtering strategy could improve the comprehensive characterization efficiency of complex components in spices.

Insights into Characteristic Volatiles in Wuyi Rock Teas with Different Cultivars by Chemometrics and Gas Chromatography Olfactometry/Mass Spectrometry

Wuyi rock tea (WRT) is one of the most famous subcategories of oolong tea, exhibiting distinct aroma characteristics with the application of different cultivars. However, a comprehensive comparison of the characteristic volatiles among WRTs with different cultivars has rarely been carried out. In this study, non-targeted analyses of volatile fragrant compounds (VFCs) and targeted aroma-active compounds in WRTs from four different cultivars were performed using chemometrics and gas chromatography olfactometry/mass spectrometry (GC-O/MS). A total of 166, 169, 166, and 169 VFCs were identified for Dahongpao (DHP), Rougui (RG), Shuixian (SX), and Jinfo (JF), respectively; and 40 components were considered as the key differential VFCs among WRTs by multivariate statistical analysis. Furthermore, 56 aroma-active compounds were recognized with predominant performances in "floral & fruity", "green & fresh", "roasted and caramel", "sweet", and "herbal" attributes. The comprehensive analysis of the chemometrics and GC-O/MS results indicated that methyl salicylate, p-cymene, 2,5-dimethylpyrazine, and 1-furfurylpyrrole in DHP; phenylethyl alcohol, phenethyl acetate, indole, and (E)-β-famesene in RG; linalool, phenethyl butyrate, hexyl hexanoate, and dihydroactinidiolide in JF; and naphthalene in SX were the characteristic volatiles for each type of WRT. The obtained results provide a fundamental basis for distinguishing tea cultivars, recombination, and simulation of the WRT aroma.

Exploring the Promotive Effects and Mechanisms of Different Polyphenolic Extracts from Prinsepia utilis Royle Seed Shell on Tyrosinase

Prinsepia utilis Royle (P. utilis) is commonly used as a food ingredient and herbal medicine according to folk records, yet little research has been done on the seed shell, a processing waste. The aim of this study was to investigate the distribution of polyphenolic components and the tyrosinase activation activity of different extracts from the seed shell by UHPLC-ESI-HRMS/MS, in vitro tyrosinase activity assay, molecular docking and molecular dynamics. A total of 16 phytochemicals were identified, of which (+)-catechin and (-)-epicatechin were the major polyphenolic compounds. Both the esterified and insoluble bound polyphenols exhibited tyrosinase activation activity, and the esterified polyphenols showed better tyrosinase activation activity. (+)-Catechin and (-)-epicatechin might be the main activators of tyrosinase, both of which may act as substrate to affect tyrosinase activity. By molecular docking and molecular dynamics simulation studies, (+)-catechin and (-)-epicatechin can be efficiently and stably bound to the tyrosinase active site through hydrogen bonds, van der Waals forces and π-bonds. The results of this study may not only provide a scientific basis for exploring P. utilis seed shell as a potential activator of tyrosinase, but also contribute to the high value utilization of P. utilis processing by-products.

Variation in Volatile Compounds of Raw Pu-Erh Tea upon Steeping Process by Gas Chromatography-Ion Mobility Spectrometry and Characterization of the Aroma-Active Compounds in Tea Infusion Using Gas Chromatography-Olfactometry-Mass Spectrometry

Steeping process is an important factor for aroma release of tea, which has rarely been investigated for the aroma changes of raw Pu-erh tea (RAPT). In addition, the comprehensive aroma characteristics identification of RAPT infusion is necessary. In this study, GC-IMS coupled with principal component analysis (PCA) was used to clarify the difference of volatile profiles during the steeping process of RAPT. Furthermore, the volatiles contained in the RAPT infusion were extracted by three pretreatment methods (HS-SPME, SBSE, and SAFE) and identified using GC-O-MS. According to the odor activity value, 28 of 66 compounds were categorized as aroma-active compounds. Aroma recombination and omission experiments showed that "fatty", "green", "fruity", and "floral" are considered to be the main aroma attributes of RAPT infusion with a strong relationship with 1-octen-3-one, 1-octen-3-ol, (E)-2-octenal, β-ionone, linalool, etc. This study will contribute a better understanding of the mechanism of the RAPT steeping process and volatile generation.

Phytochemical Compounds, Antioxidant, and Digestive Enzymes Inhibitory Activities of Different Fractions from Ginkgo biloba L. Nut Shells

This study was designed to investigate the phytochemical compounds, antioxidant, and digestive enzymes inhibitory activities of the free (F), esterified (E), and insoluble-bound (IB) fractions from Ginkgo biloba L. nut shells. Results showed that a total of twelve compounds were detected in G. biloba nut shells by using UHPLC-ESI-HRMS/MS, including two kinds of organic acids, three kinds of phenolic acids, three kinds of flavonoids, and four kinds of terpene lactones. The F fraction contained all identified compounds and had the highest contents of the total phenolics and total flavonoids. All of the three different fractions exhibited good DPPH radical and ABTS radical cation scavenging activities and strong inhibitory effects on the generation of intracellular reactive oxygen species (ROS). Moreover, these three fractions also had good inhibitory effects towards α-glucosidase and pancreatic lipase. Among the three fractions, the F fraction possessed the strongest bioactivities. The findings obtained in the current study may provide some insights and bases for the further investigation and application of G. biloba nut shells in clinical medicine or the nutraceutical industry.

Water Caltrop (Trapa quadrispinosa Roxb.) Husk Improves Oxidative Stress and Postprandial Blood Glucose in Diabetes: Phenolic Profiles, Antioxidant Activities and α-Glycosidase Inhibition of Different Fractions with In Vitro and In Silico Analyses

The aim of this study was to investigate the phenolic profiles, antioxidant activities and α-glycosidase inhibitory activities of three different phenolic fractions from water caltrop (Trapa quadrispinosa Roxb.) husk and to further explore the predominant compounds and their mechanisms on α-glycosidase inhibition by virtual screening and molecular dynamics. A total of 29 substances were identified and quantified in this study. Tannins were the main constituents of water caltrop husk extract. All of the free phenolic (FP), esterified phenolic (EP) and insoluble-bound phenolic (BP) fractions exhibited good antioxidant activities, and the BP had the highest radical scavenging ability with IC50 values of 0.82 ± 0.12 μg/mL (ABTS) and 1.15 ± 0.02 μg/mL (DPPH), respectively (p < 0.05). However, compared with the EP and BP, the FP showed the strongest inhibition towards the α-glycosidase and the IC50 value of FP was 1.43 ± 0.12 μg/mL. The 1,2,6-trigalloylglucose and α-glycosidase complex had better root mean square deviations (RMSD) stability via molecular dynamics simulation study. Results obtained from this study may provide a good potential natural resource for the improvement of oxidative stress injury and blood glucose control in diabetes mellitus, which could expand the use of water caltrop husk and improve its economic value.

Flavor of tea (Camellia sinensis): A review on odorants and analytical techniques

Tea is among the most consumed nonalcoholic beverages worldwide. Understanding tea flavor, in terms of both sensory aspects and chemical properties, is essential for manufacturers and consumers to maintain high quality of tea products and to correctly distinguish acceptable or unacceptable products. This article gives a comprehensive review on the aroma and off-flavor characteristics associated with 184 odorants. Although many efforts have been made toward the characterization of flavor compounds in different types of tea, modern flavor analytical techniques that affect the results of flavor analysis have not been compared and summarized systematically up to now. Thus, the overview mainly provides the instrumental flavor analytical techniques for both aroma and taste of tea (i.e., extraction and enrichment, qualitative, quantitative, and chemometric approaches) as well as descriptive sensory analytical methodologies for tea, which is helpful for tea flavor researchers. Flavor developments of tea evolved toward time-saving, portability, real-time monitoring, and visualization are also prospected to get a deeper insight into the influences of different processing techniques on the formation and changes of flavor compounds, especially desired flavor compounds and off-flavor substances present at (ultra)trace amounts in tea and tea products.

Identification and Quantification of Chlorogenic Acids from the Root Bark of Acanthopanax gracilistylus by UHPLC-Q-Exactive Orbitrap Mass Spectrometry

The purpose of this study is to identify and quantify the chlorogenic acids (CGAs) from the root bark of Acanthopanax gracilistylus, which is conventionally regarded as a tonic in folk Chinese Traditional medicine. The effective methods for identification and quantification analysis of CGAs were developed based on ultra high performance liquid chromatography-Q-exactive orbitrap mass spectrometry (UHPLC-Q-Orbitrap MS) in parallel reaction monitoring (PRM) and selected reaction monitoring (SIM), which showed high sensitivity and resolution for screening and quantifying compounds. The root bark of A. gracilistylus was extracted under ultrasonication with 70% methanol. Ultimately, a for total of 70 CGAs, 64 of these were tentatively identified for the first time. Moreover, a methodological study of seven kinds of CGAs was carried out. The proposed procedure was optimized and validated in terms of selectivity, linearity of analytical curves (r ² > 0.990), accuracy (recovery range from 96.7 to 105%), and repeatability (relative standard deviation <5%). Then it was applied to determine the content of the CGAs in A. gracilistylus roots from 66 of different batches. The total CGAs was quantified in a range between 2.150 and 33.51 mg/g, which could be considered as excellent source of natural bioactive compound. The result was extremely useful for understanding the bioactive substance and quality control of A. gracilistylus in depth.

Mycotoxins in Tea ((Camellia sinensis (L.) Kuntze)): Contamination and Dietary Exposure Profiling in the Chinese Population

Tea is popular worldwide with multiple health benefits. It may be contaminated by the accidental introduction of toxigenic fungi during production and storage. The present study focuses on potential mycotoxin contamination in tea and the probable dietary exposure assessments associated with consumption. The contamination levels for 16 mycotoxins in 352 Chinese tea samples were determined by ultra-performance liquid chromatography-tandem mass spectrometry. Average concentrations of almost all mycotoxins in tea samples were below the established regulations, except for ochratoxin A in the dark tea samples. A risk assessment was performed for the worst-case scenarios by point evaluation and Monte Carlo assessment model using the obtained mycotoxin levels and the available green, oolong, black, and dark tea consumption data from cities in China. Additionally, we discuss dietary risk through tea consumption as beverages and dietary supplements. In conclusion, there is no dietary risk of exposure to mycotoxins through tea consumption in the Chinese population.

Analysis of the differences in the chemical composition of monascus rice and highland barley monascus

Monascus rice (MR) and highland barley monascus (HBM), the monascus fermented products, are applied in food and medicine to reduce cholesterol and promote digestion. Due to the fermentation substrates, their compositions are different. However, the exact differences have not been reported to date. By UPLC-Q-Orbitrap HRMS analysis, multiple components of twenty batches of MR and HBM samples were identified. In total, 100 components were confirmed (e.g., monacolins, pigments, decalin derivatives, amino acids). Then, principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to filter the components of MR and HBM. In the PCA model, 88.1% of the total variance was uncovered. The OPLS-DA model showed better discrimination between MR and HBM, and the values of R²X, R²Y, and Q² were 0.837, 0.996, and 0.956, respectively. Based on the value of the variable importance in projection (VIP) and the result of the t-test, 424 components (VIP > 1, p < 0.05) were acquired. Finally, 11 differential components were selected as the characteristic compounds to discriminate between MR and HBM: the content of 9 monacolins (3-hydroxy-3,5-dihydrodehydromonacolin K, monacolin K, dehydromonacolin K, dehydromonacolin J hydroxy acid, monacophenyl, dihydromonacolin J hydroxy acid, monacolin L, dehydromonacolin J, and monacolin R) in HBM was higher than the content in MR, but the content of 2 pigments (ankaflavin and monascin) was lower in HBM and higher in MR. The findings revealed the similarities and differences in the chemical composition between MR and HBM, which is expected to provide a basis for quality control of HBM.

Targeted identification of glycosylated flavones and isomers in green tea through integrated ion-filtering strategy and mass-fragmentation characteristics based on the UPLC-Q-Orbitrap-MS/MS platform

Glycosylated flavones (GFs) are important components of green tea and have various structures and isomers. The annotation of GFs' chemical structures is challenging. Ultrahigh-performance liquid chromatography-high resolution mass spectrometry can provide informative mass ions for GF annotation. However, distinguishing the mass features of GFs from those of thousands of ions is difficult. In this study, integrated ion-filtering strategies for O- and C-glycosyl flavones were constructed, and the mass-fragmentation characteristics were summarized from GF standards. Ultimately, 29 GFs with different types of aglycones and glycosides, connection modes, and locations were annotated. According to principal component analysis and t-test results, significant differences were observed in the contents of 16 components in the two kinds of tea. Among them, the contents of 11 GFs in autumn teas were significantly higher than those in spring teas. This study provided an efficient strategy for isomer annotation in food analysis.

Assessment of Variations in Round Green Tea Volatile Metabolites During Manufacturing and Effect of Second-Drying Temperature via Nontargeted Metabolomic Analysis

Round green tea (RGT) is widely distributed and presents a high yield in China. The quality of RGT can be determined by its aroma; however, the transformation and formation of volatile metabolites during RGT processing remain unclear. In this study, 173 volatile compounds (nine categories) were identified totally from RGT via gas chromatography-mass spectrometry with infrared-assisted headspace-solid phase microextraction. These substances exhibited different changing trends during various procedures, with the most intense transformation occurring during fixation, followed by pan-frying and second drying; moreover, 51 substances were screened, mainly containing fatty acid-derived volatiles (i.e., (E)-2-hexen-1-ol, Hexanal, pentanal, hexanal) and glycoside-derived volatiles (i.e., linalool, geraniol, benzyl alcohol, benzaldehyde), and their evolution during processing was clarified. Furthermore, the effect of the second-drying temperature on volatile compound metabolism was clarified, and 90°C was the best temperature for RGT aroma. This research lays a foundation for in-depth quality control and the aroma formation mechanism of RGT.

Phytochemical profile of Tibetan native fruit "Medog lemon" and its comparison with other cultivated species in China

Tibet's native fruit resources have not been explored and remain underutilized due to geographical isolation. "Medog lemon" (ML), an ethno-species of wild citron, is an important functional food and dietary resource for the local people in southeastern Tibet. Herein comprehensive characterization of components of ML were firstly performed with an integrated strategy based on UHPLC-QE Orbitrap MS. A total of 196 components were characterized, among which 33 were detected from Citrus genus for the first time, and 55 were identified as potential new phytochemicals. The chemical comparison of ML with cultivated citron and fingered citron based on partial least squares-discriminant analysis model and univariate analysis revealed the distinct chemical composition of ML and in which more than 30 differentiated components were identified. The distinct morphological and chemical characters, as well as its good antioxidant properties, indicated ML as a potential new food resource that can be beneficial for human health.

[Comprehensive analysis of chemical constituents of tea flowers by ultra-performance liquid chromatography-high resolution mass spectrometry combined with integrated filtering strategy]

Tea flowers and fresh tea leaves are biological products of tea, but tea flower is often regarded as waste during tea production, resulting in notable waste of tea flower resources. At present, analysis of the chemical components in tea flowers focuses on single types of chemical components such as amino acids and tea polyphenols, and there are only a few reports on the simultaneous analysis of numerous chemical components in tea flowers. Researchers are not completely clear about the types and amounts of the chemical components in tea flowers; this has hindered the in-depth development and effective utilization of tea flowers. In this study, ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was used to detect the chemical constituents of tea flowers. This technique was combined with the integrated filtering strategy (IFS) of nitrogen rule filtering (NRF), mass defect filtering (MDF), and diagnostic fragment ion filtering (DFIF) for screening the characteristic mass spectra of the target chemical components. Furthermore, the chemical constituents of tea flowers were annotated with information about the retention time, MS fragmentation, and MS/MS fragmentation. All the qualitative chemical components were divided into six categories with a total of 137 chemical constituents, including 3 alkaloids, 38 flavonoids, 31 phenolic acids and their derivatives, 37 catechins and their derivatives, 18 amino acids, and 10 other components. The internal standard method was used to quantify all the qualitative chemical components. The quantitative results showed that the amounts of the six kinds of chemical components in tea flowers were as follows: amino acids, 9371.42 μg/g; catechins and their derivatives, 9068.43 μg/g; phenolic acids and their derivatives, 8696.92 μg/g; alkaloids, 4392.52 μg/g; flavonoids, 1192.88 μg/g; and others, 139.94 μg/g. Quality control samples were used to evaluate the stability of the instrument and the repeatability of the tested data. Nine representative chemical components with high, medium, and low contents in tea were selected, and the relative standard deviation (RSD) of the results was used to evaluate the repeatability of the data. These nine chemical constituents are selected from amino acids, alkaloids, flavonoids, phenolic acids and their derivatives, catechins and their derivatives, and other components, and the response intensities were different. The relative standard deviations of the nine chemical components were in the range of 2.11% to 12.17%. The above results demonstrated the good stability of the instrument and excellent repeatability of the test data. Chlorogenic acid components (CGAs) and glycosylated quercetin components (GQs) were used as two representative components to explain the entire process of extracting the target compounds by IFS. CGAs comprise a class of special esters formed by the esterification of cinnamic acid derivatives with quinic acid as the parent structure. The most common cinnamic acid derivatives are p-coumaric acid, caffeic acid, and ferulic acid. On the one hand, according to the above information and the different positions and degree of quinic acid esterification, the CGAs were structurally classified as monosubstituted CGAs (Mono-CGAs), disubstituted CGAs (Di-CGAs), and trisubstituted CGAs (Tri-CGAs), and three different mass defect filtering windows were set. Therefore, 751 possible target components were selected from 3537 mass spectra in accordance with the nitrogen rule. On the other hand, 22 target components in accordance with the nitrogen rule were obtained by further screening the m/z 191.0551 ion as the diagnostic fragment ion of the CGAs. Combining the overall analytical data with the above mass defect filtering and diagnostic fragment ion filtering screening results, nine target CGAs were selected and characterized based on the MS information. This study reveals the types and amounts of the chemical components accumulated in tea flowers, thus providing valuable information and serving as data reference for the in-depth development and effective utilization of tea flowers.

Development of a Novel UPLC-MS/MS Method for the Simultaneous Determination of 16 Mycotoxins in Different Tea Categories

The contamination of potential mycotoxins in tea production and consumption has always been a concern. However, the risk monitoring on multiple mycotoxins remains a challenge by existing methods due to the high cost and complex operation in tea matrices. This research has developed a simple ultra-performance liquid chromatography-tandem mass spectrometry strategy based on our homemade purification column, which can be applied in the detections of mycotoxins in complex tea matrices with high-effectively purifying and removing pigment capacity for 16 mycotoxins. The limits of detection and the limits of quantification were in the ranges of 0.015~15.00 and 0.03~30.00 µg·kg⁻¹ for 16 mycotoxins, respectively. Recoveries from mycotoxin-fortified tea samples (0.13~1200 µg·kg⁻¹) in different tea matrices ranged from 61.27 to 118.46%, with their relative standard deviations below 20%. Moreover, this method has been successfully applied to the analysis and investigation of the levels of 16 mycotoxins in major categories of tea and the monitoring of multiple mycotoxins in processed samples of ripened Pu-erh. In conclusion, the proposed strategy is simple, effective, time-saving, and low-cost for the determination of a large number of tea samples.

Analysis of the characteristic compounds of Citri Sarcodactylis Fructus from different geographical origins

INTRODUCTION

Citri Sarcodactylis Fructus (CSF) is widely used as a food ingredient and a traditional Chinese medicine. In China, CSF is cultivated in many places, including Sichuan, Guangdong, Zhejiang, and Fujian provinces. The types and chemical contents of CSF from different origins may vary greatly due to the difference in climate and environmental conditions. Therefore, comparing the chemical composition of CSF from various places is vital.

OBJECTIVE

To rapidly select potential characteristic compounds for differentiating CSF from different origins.

MATERIAL AND METHODS

Thirty-one batches of CSF samples from different regions were analysed using ultra-performance liquid chromatography with hybrid quadrupole-orbitrap high-resolution mass spectrometry. Thereafter, chemometric methods, including principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA), were employed to find differential metabolites among the CSF samples from various origins.

RESULTS

PCA revealed 77.9% of the total variance and divided all CSF samples into three categories corresponding to their origins. OPLS-DA displayed better discrimination of CSF from different sources, with R² X, R² Y, and Q² of 0.801, 0.985, and 0.849, respectively. Finally, 203 differential metabolites were obtained from CSF from different origins using the variable importance in projection of the OPLS-DA model, 30 of which were identified, and five coumarin compounds were selected as marker compounds discriminating CSF from different origins.

CONCLUSION

This work provides a practical strategy for classifying CSF from different origins and offers a research foundation for the quality control of CSF.

The Impact of Citrus-Tea Cofermentation Process on Chemical Composition and Contents of Pu-Erh Tea: An Integrated Metabolomics Study

Ganpu tea, an emerging pu-erh compound tea, which is cofermented with the peel of Citrus reticulata "Chachi," has been widely favored by Chinese consumers due to its potential health effects and distinct flavor and taste. So far, the influence of this cofermentation procedure on the chemical profile of pu-erh tea has barely been addressed yet. In this work, an ultra-high-performance liquid chromatography-Q Exactive Orbitrap mass spectrometry (UHPLC-QE Orbitrap MS)-based qualitative and quantitative method combined with multivariate analysis was conducted to comprehensively investigate the chemical changes in pu-erh tea after cofermented with Citrus peel. A total of 171 compounds were identified based on a three-level strategy, among which seven phenolic acids, 11 flavan-3-ols, and 27 flavonoids and flavonoid glycosides were identified from pu-erh tea for the first time. Eighty-nine main constituents were selected for further quantitative analysis using a validated method. Both the principal component analysis (PCA) of untargeted metabolomics and orthogonal partial least squares discriminant analysis (OPLS-DA) models of targeted components revealed the significant chemical profile disparity between the raw pu-erh tea and Ganpu tea. It showed that Citrus tea cofermentation process significantly decreased the total contents of phenolic acids, flavan-3-ols, and flavonoid aglycones, while most of the quercetin glycosides and myricetin glycosides as well as the vitexin were significantly increased. In addition, hesperidin, a flavonoid glycoside only existed in Citrus, was first found in pu-erh tea after cofermented with Citrus. This study clearly profiled the chemical composition and content changes of pu-erh tea after cofermented with Citrus peel, which revealed that Citrus tea cofermentation process further accelerated the fermentation of pu-erh tea and improved the unique flavor of tea.

Quality chemical analysis of crush-tear-curl (CTC) black tea from different geographical regions based on UHPLC-Orbitrap-MS

Crush-tear-curl (CTC) black tea is a popular beverage, owing to its unique taste characteristics and health benefits. However, differences in the taste quality and chemical profiles of CTC black tea from different geographical regions remain unclear. In this study, 28 CTC black tea samples were collected from six geographical regions and analyzed using electronic tongue and ultrahigh performance liquid chromatography-Orbitrap-mass spectroscopy. The e-tongue analysis indicated that each region's CTC black tea has its own relatively prominent taste characteristics: Sri Lanka (more umami and astringent), North India (more umami), China (more sweetness and astringent), South India (moderate umami and sweetness), and Kenya (moderate umami and astringent). Based on multivariate statistical analysis, 78 metabolites were tentatively identified and used as potential markers for CTC black tea of different origins, mainly including amino acids, flavone/flavonol glycosides, and pigments. Different metabolites, which contributed to the taste characteristics of CTC black tea, were clarified by partial least squares regression correlation analysis. Our findings may serve as useful references for future studies on origin traceability and quality characteristic determination of CTC black teas. PRACTICAL APPLICATION: This study provides useful references for future studies on the origin traceability and taste characteristic determination of CTC black teas from different geographical regions.

Rat plasma protein binding of kaempferol-3-O-rutinoside from Lu'an GuaPian tea and its anti-inflammatory mechanism for cardiovascular protection

Previous study found a high content of kaempferol-3-O-rutinoside (KR) in Lu'an GuaPian tea, however, the rat plasma protein binding and mechanism of KR for cardiovascular protection are unclear. Thus, we studied plasma protein binding using ultrafiltration followed by UPLC, and screened its inhibition against LPS-induced inflammation injury in vitro as well as the underlying mechanism by molecular docking and western blot. KR showed over 74% plasma protein binding ratio. Furthermore, KR may act on the toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88). In vitro experiments showed that KR decreases the overexpression of TLR4, MyD88, and nuclear factor-κB (NF-κB), which further validates the molecular docking results, suggesting that KR could block TLR4/MyD88/NF-κB signaling. These results indicate that KR could be a potential active agent in the protection of myocardial injury. PRACTICAL APPLICATIONS: Health benefits of tea are largely dependent on the intake of flavonoids. Flavonoids are a group of compounds beneficial to cardiovascular disease and an important part of "functional foods." Lu'an GuaPian tea is mainly produced in Lu'an City, Anhui Province and is one of the top 10 famous teas in China. Kaempferol-3-O-rutinoside in Lu'an GuaPian has good hypoglycemic effect, mainly manifested in a strong inhibition of α-glucosidase and α-amylase activities. Present study showed that kaempferol-3-O-rutinoside could block TLR4/MyD88/NF-κB signaling, suggesting that it could be a potential active agent in the protection of myocardial injury.

Diagnostic ion filtering targeted screening and isolation of anti-inflammatory iridoid glycosides from Hedyotis diffusa

Efficient and targeted screening and isolation of bioactive compounds from complex natural products is still a challenging work. Herein, diagnostic ion filtering based high-performance liquid chromatography-quadrupole time-of-flight-tandem mass spectrometry was firstly developed to screen six main iridoid glycosides from Hedyotis diffusa. Then, online extraction-high-speed counter current chromatography was proposed for targeted enrichment and preparative isolation using ethyl acetate/n-butanol/water (4.5:0.5:5, v/v/v) as solvent system. After that, Sephadex LH-20 column chromatography using methanol as solvent system was selected for further purification of six iridoid glycosides with purities over 98%. They were finally identified as monotropein, desacetylasperuloside acid, asperuloside, 6-O-(Z)-p-coumaroyl scandoside methyl ester, 6-O-(Z)-feruloyl scandoside methyl ester, and 6-O-(E)-p-coumaroyl scandoside methyl ester. And their anti-inflammatory activities were evaluated and confirmed by lipopolysaccharide activated RAW 264.7 macrophages. Obviously, the results provide a scientific basis for the potential applications of H. diffusa, and the developed methodology is efficient and reliable for targeted screening and isolation of bioactive compounds from natural products.

Development and validation of the one-step purification method coupled to LC-MS/MS for simultaneous determination of four aflatoxins in fermented tea

Aflatoxin B₁ is the potential chemical contaminant of most concern during the production and storage of fermented tea. In this work, a simple, fast, sensitive, accurate, and inexpensive method has been developed and validated for the simultaneous detection of four aflatoxins in fermented tea based on a modified sample pretreatment method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Aflatoxins were extracted using acetonitrile and purified using mixed fillers (carboxyl multiwalled carbon nanotubes, hydrophilic-lipophilic balance, silica gel). Under optimum LC-MS conditions, the limits of quantification (LOQs) were 0.02-0.5 µg·kg^-1. Recoveries from aflatoxins-fortified tea samples (1-12 µg·kg^-1) were in the range of 78.94-105.23% with relative standard deviations (RSDs) less than 18.20%. The proposed method was applied successfully to determine aflatoxin levels in fermented tea samples.

Determination of 4 psychoactive substances in tea using ultra high performance liquid chromatography combined with the quadrupole time-of-flight mass spectrometry

In this study, a method for the qualification and quantification of 4 psychoactive substances in tea using ultra high performance liquid chromatography coupled with the quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) has been developed. Tea samples were extracted by a 50% (v/v) methanol-water solution, and then separated by an ACQUITY UPLC BEH Shield RP18 column using a binary solvent system by gradient elution. The analytes were determined by Q-TOF/MS in TOFMS and information-dependent acquisition (IDA)-MS/MS mode. The results showed that the mass accuracy error of the 4 psychoactive substances were lower than 5.0 × 10-6, and a good linear relationship was observed in the range of 0.5-500 μg L-1 and correlation coefficient was higher than 0.9990. The LOD was in the range of 0.005-0.020 mg kg-1 and the LOQ was in the range of 0.010-0.040 mg kg-1. The recovery of the method was in range of 80.14-93.25% with spike levels of 0.010-0.400 mg kg-1, and relative standard deviations were lower than 10%. The method was simple, specific and reliable. It has been successfully used for the detection of 4 psychoactive substances in tea samples.

Chemometric Analysis of Extracts and Fractions from Green, Oxidized, and Microbial Fermented Teas and Their Correlation to Potential Antioxidant and Anticancer Effects

Previous reports on phytochemicals in green tea (GT) and processed teas mainly focused on more representative compounds such as catechins. Here, we focus on the insignificantly studied non-catechin components in tea extracts, and explore the multivariate correlation between diverse phenolic compounds in tea and the in vitro antioxidant and anticancer effects. Extracts from GT and four types of processed teas were further divided into hydrophilic and hydrophobic fractions, whose phenolic compositions and antioxidant capacities were quantified using HPLC-MS and three antioxidant assays, respectively. For three types of teas, the anticancer effects of their extracts and fractions were assessed using cancer cell lines. The hydrophobic fractions had lower antioxidant capacities than the corresponding hydrophilic fractions, but exhibited superior antiproliferative effects on cancer cells compared with the whole extract and the hydrophilic fraction. Partial least squares-discriminant analysis revealed a strong correlation between the anticancer effects and the theaflavins and flavonols. Therefore, in addition to catechins, the hydrophobic fraction of tea extracts may have beneficial health effects.