Identification of key metabolites based on non-targeted metabolomics and chemometrics analyses provides insights into bitterness in Kucha [Camellia kucha (Chang et Wang) Chang]

Metabolomic insights into the Arabica-like flavour of stenophylla coffee and the chemistry of quality coffee

Stenophylla coffee, an undomesticated species from Upper West Africa, is of commercial interest due to its high heat tolerance and Arabica-like flavour. To investigate the chemical basis of flavour similarity, we analysed unroasted coffee bean samples using liquid chromatography-mass spectrometry (LC-MS) and applied metabolomics approaches to compare chemical profiles. We report similarities between Arabica and stenophylla in the relative levels of several key compounds linked to coffee flavour, including caffeine, trigonelline, sucrose and citric acid. Differences in their chemical profiles were also observed, especially in their diterpenoid and hydroxycinnamic acid profiles. We report the additional novel finding that theacrine occurs in stenophylla, which is the first record of this alkaloid in coffee beans. For stenophylla, the dissimilarities in chemical compound composition (compared to Arabica) may offer opportunities for a better understanding of the chemical basis of high-quality coffee and sensory diversification.

Supercritical CO2 Extraction of Bioactive Compounds from Corn Grains (Zea mays L., Hybrid Pri-15-7-16) with Metabolomic Profiling and Confocal Laser Microscopy

This study aimed to optimize supercritical CO2 extraction conditions, analyze bioactive compounds, and visualize their distribution in corn grains (Zea mays L., hybrid Pri-15-7-16). The optimal extraction conditions were identified as a pressure of 200 bar and a temperature of 55 °C, yielding 2.2 mg/g of bioactive compounds. The distribution of autofluorescent compounds within corn grain tissues was visualized using confocal laser scanning microscopy. Image analysis showed that the pericarp and aleurone layer cell walls were rich in autofluorescent compounds, while the endosperm cell walls exhibited low autofluorescence. Metabolomic analysis, combining high-performance liquid chromatography and mass spectrometry, identified 44 compounds in the extracts, including 30 polyphenolic compounds from subgroups such as polyphenolic acids, flavones, flavan-3-ols, flavonols, and anthocyanidins as well as 14 compounds from other chemical groups, including amino acids and fatty acids.

Supercritical Extraction and Identification of Bioactive Compounds in Dryopteris fragrans (L.) Schott

Background: This is a comparative metabolomic study of the medicinal plant Dryopteris fragrans (L.) Schott from the family Dryopteridaceae Herter (or Aspidiaceae Mett. ex Frank) growing under cold pole conditions in the Oymyakon region of the Republic of Sakha (Yakutia). Methods: The aerial parts of D. fragrans were subjected to extraction using supercritical CO2 extraction and maceration methods. Several experimental conditions were investigated, including a pressure range of 50-300 bar and a temperature range of 31-60 °C. A 1% volume of ethanol was used as a co-solvent in the liquid phase of the extraction. Results: The most effective D. fragrans extraction conditions were 200 Bar pressure and a temperature of 55 °C. Tandem mass spectrometry was used to detect the target analytes. A total of 141 bioactive compounds (86 compounds from the polyphenol group and 55 compounds from other chemical groups) were tentatively identified in extracts of aerial parts of D. fragrans. Among these, thirty chemical constituents from the polyphenol group were identified for the first time. Other compound classes that were newly identified in D. fragrans include naphthoquinones (5,8-dihydroxy-6-methyl-2,3-dihydro-1,4-naphthoquinone, 1,8-dihydroxy-anthraquinone, 1,4,8-trihydroxyanthraquinone, chrysophanol, etc.), diterpenoids (tanshinone IIa, cryptotanshinone, isocryptotanshinone II, tanshinone IIb, etc.), polysaccharides, triterpenoids, and sesquiterpenes. Conclusions: These results highlight that D. fragrans is rich in bioactive compounds and put forward several newly detected compounds for further investigation.

Evaluation of key taste components in Huangjin green tea based on electronic tongue technology

A random forest algorithm combined with correlation analysis, was employed to identify key taste compounds in Huangjin green tea by using an electronic tongue. A total of 45 commercial Huangjin green teas were analysed for their amino acids, catechins, gallic acid, and caffeine using an amino acid analyser and HPLC. In this study, taste compounds of 30 were quantified, and 16 of these compounds exhibited taste activity values greater than 1 in the tea samples, including 6 amino acids, 8 catechins, as well as gallic acid and caffeine. Among these compounds, 5 compounds showed relatively high importance and strong correlations (P < 0.05) with the response of electronic tongue; specific for theanine, glutamic acid, lysine, gallocatechin, and catechin. A taste reconstruction experiment further confirmed that these 5 compounds significantly contributed to the overall taste profile, particularly enhancing the umami flavour.

Investigating the effects of thermal processing on bitter substances in atemoya (Annona cherimola × Annona squamosa) through sensory-guided separation

Atemoya (Annona cherimola × Annona squamosa) is a specialty crop in Taiwan. Thermal treatment induces bitterness, complicating seasonal production adjustments and surplus reduction. In this research, sensory-guided separation, metabolomics, and orthogonal partial least squares discrimination analysis (OPLS-DA) are used for identifying the bitterness in atemoya which originates from catechins, epicatechin trimers, and proanthocyanidins. Different thermal treatments (65 °C, 75 °C, and 85 °C) revealed that the glucose and fructose contents in atemoya significantly decreased, while total phenols, flavonoids, and tannins significantly increased. The concentration of 5-hydroxymethylfurfural (5-HMF) increased from 23.16 ng/g in untreated samples to 400.71 ng/g (AP-65), 1208.59 ng/g (AP-75), and 2838.51 ng/g (AP-85). However, these levels are below the 5-HMF bitterness threshold of 3780 ng/g. Combining mass spectrometry analysis with sensory evaluation, OPLS-DA revealed that atemoya treated at 65 °C, 75 °C, and 85 °C exhibited significant bitterness, with the main bitter components being proanthocyanidin dimers and trimers.

Application of Supercritical CO2 Extraction and Identification of Polyphenolic Compounds in Three Species of Wild Rose from Kamchatka: Rosa acicularis, Rosa amblyotis, and Rosa rugosa

A comparative metabolomic study of three varieties of wild Rosa (Rosa acicularis, Rosa amblyotis, and Rosa rugosa) from a Kamchatka expedition (2024) was conducted via extraction with supercritical carbon dioxide modified with ethanol (EtOH), and detection of bioactive compounds was realized via tandem mass spectrometry. Several experimental conditions were investigated in the pressure range 50-350 bar, with the used volume of co-solvent ethanol in the amount of 2% in the liquid phase at a temperature in the range of 31-70 °C. The most effective extraction conditions are the following: pressure 200 Bar and temperature 55 °C for Rosa acicularis; pressure 250 Bar and temperature 60 °C for Rosa amblyotis; pressure 200 Bar and temperature 60 °C for Rosa rugosa. Three varieties of wild Rosa contain various phenolic compounds and compounds of other chemical groups with valuable biological activity. Tandem mass spectrometry (HPLC-ESI-ion trap) was applied to detect the target analytes. A total of 283 bioactive compounds (two hundred seventeen compounds from the polyphenol group and sixty-six compounds from other chemical groups) were tentatively identified in extracts from berries of wild Rosa. For the first time, forty-eight chemical constituents from the polyphenol group (15 flavones, 14 flavonols, 4 flavan-3-ols, 3 flavanones, 1 phenylpropanoid, 2 gallotannins, 1 ellagitannin, 4 phenolic acids, 1 dihydrochalcone, and 3 coumarins) were identified in supercritical extracts of R. acicularis, R. amblyotis, and R. rugosa.

Evolution of the biochemistry underpinning purine alkaloid metabolism in plants

Purine alkaloids are naturally occurring nitrogenous methylated derivatives of purine nucleotide degradation products, having essential roles in medicine, food and various other aspects of our daily lives. They are generated through convergent evolution in different plant species. The pivotal reaction steps within the purine alkaloid metabolic pathways have been largely elucidated, and the convergent evolution of purine alkaloids has been substantiated through bioinformatic, biochemical and other research perspectives within S-adenosyl-ʟ-methionine-dependent N-methyltransferases. Currently, the biological and ecological roles of purine alkaloids, further refinement of the purine alkaloid metabolic pathways and the investigation of purine alkaloid adaptive evolutionary mechanisms continue to attract widespread research interest. The exploration of the purine alkaloid metabolic pathways also enhances our comprehension of the biochemical mechanism, providing insights into inter-species interactions and adaptive evolution and offering potential value in drug development and agricultural applications. Here, we review the progress of research in the distribution, metabolic pathway elucidation and regulation, evolutionary mechanism and ecological roles of purine alkaloids in plants. The opportunities and challenges involved in elucidating the biochemical basis and evolutionary mechanisms of the purine alkaloid metabolic pathways, as well as other research aspects, are also discussed. This article is part of the theme issue 'The evolution of plant meta-bolism'.

Investigation of non-volatile metabolite variations during round green tea processing and effect of pan-frying degree using untargeted metabolomics and objective quantification

Round green tea (RGT) presents unique properties and is widely distributed in China, and during processing, it undergoes dynamic changes in non-volatile metabolites (NVMs), which are poorly understood. Utilizing UHPLC-Q-Exactive/MS analysis, this study comprehensively characterized 216 NVMs during RGT processing and identified fixation and pan-frying as key processes influencing NVMs. Additionally, 23 key differential NVMs were screened, with amino acid and flavonoid metabolism highlighted as key metabolic pathways for RGT taste and color quality. The impact of pan-frying degree on shape, color, and taste was also explored. Moderate pan-frying led to optimal results, including a tight and round shape, green and bright color, mellow and umami taste, and reduced astringent and bitter taste NVMs, including epigallocatechin gallate, procyanidin B2, myricetin 3-O-galactoside, quinic acid, strictinin, phenylalanine, and theobromine. This study addresses the NVM research gap in RGT processing, thus providing a technical foundation for the precision-oriented processing of high-quality tea.

Exploration of the mechanism of temperature influence on bitter taste of theacrine by activating human bitter taste receptor hTAS2R14

Theacrine, a purine alkaloid derived from Camellia assamica var. kucha, has a distinct bitter taste. Our previous study found the lower recognition threshold of theacrine at 25 °C than 45 °C. This study aims to investigate the bitterness characterizations of theacrine at aforementioned temperatures and its taste perception mechanism. Sensory analysis exhibited higher bitterness intensity for theacrine at 25 °C than 45 °C. Subsequently, flow cytometry was performed to verify the above characterization at the cellular level. It revealed that theacrine could activated the bitter receptor hTAS2R14 and the calcium signal at 25 °C was higher than 45 °C. Ultimately, the interaction mechanism was studied by molecular dynamics simulations, indicating that the conformation of theacrine-hTAS2R14 had a higher binding capacity and better stability at 25 °C. Overall, temperature affected the binding of theacrine to the bitter receptor hTAS2R14, resulting in the stronger bitterness intensity of theacrine at 25 °C than 45 °C.

Multivariate approach to assess the bioactive compounds of Atractylodes chinensis (DC.) Koidz in different harvest periods

BACKGROUND

The Atractylodes chinensis (DC.) Koidz (A. chinensis) Chinese herb possesses numerous therapeutic properties and is extensively utilized in the pharmaceutical industry. Its quality is closely associated with the harvest periods. However, the optimal quality and harvest periods of A. chinensis remain elusive.

METHODS

The bioactive compounds of perennial A. chinensis were detected by ultra-high-performance liquid chromatography coupled with quadrupole Orbitrap mass spectrometry (UHPLC-Q-Orbitrap/MS) metabolomics, and differentially abundant compounds were selected by multivariate statistical analysis. Then, variations in the content of differential compounds in samples harvested at different periods were analyzed, while correlation analysis was carried out on the differential compounds to determine the suitable harvest period for distinct components.

RESULTS

A total of 61 bioactive compounds were detected in all samples, grouped into 9 known classes. The results revealed that the chemical compositions of A. chinensis at different harvest periods were significantly different. The volatile oil content in the four-year-old and five-year-old samples was relatively high, at 31.92 mg/g and 32.42 mg/g, respectively. There were also significant differences in the content of the six active ingredients, for example, the five-year-old sample had the highest content of atractylodin (4.38 mg/g). Indeed, the harvest period was correlated with the abundance of most bioactive compounds. Specifically, quinquennial samples were significantly negatively correlated with the abundance of organic acids and aliphatics while moderately positively correlated with the abundance of other classes of bioactive compounds.

CONCLUSIONS

According to the results, the ideal harvest time for atractylenolide Ⅲ was 3 years. Regarding organic acids, the optimal harvest time was around 2-3 years. Taken together, these results offer valuable insights to producers for optimizing the harvest period for A. chinensis.

Genus Ribes: Ribes aureum, Ribes pauciflorum, Ribes triste, and Ribes dikuscha-Comparative Mass Spectrometric Study of Polyphenolic Composition and Other Bioactive Constituents

This study presents the metabolomic profiles of the four Ribes species (Ribes pauciflorum Turcz., Ribes triste Pall., Ribes dicuscha Fisch., and Ribes aureum Purch.). The plant material was collected during two expeditions in the Russian Far East. Tandem mass spectrometry was used to detect target analytes. A total of 205 bioactive compounds (155 compounds from polyphenol group and 50 compounds from other chemical groups) were tentatively identified from the berries and extracts of the four Ribes species. For the first time, 29 chemical constituents from the polyphenol group were tentatively identified in the genus Ribes. The newly identified polyphenols include flavones, flavonols, flavan-3-ols, lignans, coumarins, stilbenes, and others. The other newly detected compounds in Ribes species are the naphthoquinone group (1,8-dihydroxy-anthraquinone, 1,3,6,8-tetrahydroxy-9(10H)-anthracenone, 8,8'-dihydroxy-2,2'-binaphthalene-1,1',4,4'-tetrone, etc.), polyhydroxycarboxylic acids, omega-3 fatty acids (stearidonic acid, linolenic acid), and others. Our results imply that Ribes species are rich in polyphenols, especially flavanols, anthocyanins, flavones, and flavan-3-ols. These results indicate the utility of Ribes species for the health and pharmaceutical industry.

A new insight into the key matrix components for aftertaste in Ampelopsis grossedentata (vine tea) infusion: From the intensity and duration of taste profiles using non-targeted metabolomics and molecular simulation

The aftertaste with a prolonged duration in ampelopsis grossedentata infusion (AGTI) is easily perceived, however, its formation mechanism is unclear. Therefore, aftertaste-A and richness were confirmed as the characteristic aftertaste of AGTI through sensory evaluation and electronic tongue. Moreover, 5-KETE, theobromine, etc., metabolites were identified as the differential components between AGTI and green tea infusion. Among them, p-coumaroyl quinic acid, xanthine etc., and proline, dihydromyricetin, etc., components contributed more to the formation of aftertaste-A and richness, respectively. Further, the bonding between characteristic metabolites for aftertaste in AGTI with their receptors were shown to be more stable using molecular docking, compared to metabolites related to typical taste profiles. The aftertaste in AGTI was more easily perceived by saltiness components or in NaCl system by molecular simulation. This study offers novel insight into the interaction mechanism of aftertaste in tea infusion and will contribute to further study on aftertaste for other foods.

Bitter flavors and bitter compounds in foods: identification, perception, and reduction techniques

Bitterness is one of the five basic tastes generally considered undesirable. The widespread presence of bitter compounds can negatively affect the palatability of foods. The classification and sensory evaluation of bitter compounds have been the focus in recent research. However, the rigorous identification of bitter tastes and further studies to effectively mask or remove them have not been thoroughly evaluated. The present paper focuses on identification of bitter compounds in foods, structural-based activation of bitter receptors, and strategies to reduce bitter compounds in foods. It also discusses the roles of metabolomics and virtual screening analysis in bitter taste. The identification of bitter compounds has seen greater success through metabolomics with multivariate statistical analysis compared to conventional chromatography, HPLC, LC-MS, and NMR techniques. However, to avoid false positives, sensory recognition should be combined. Bitter perception involves the structural activation of bitter taste receptors (TAS2Rs). Only 25 human TAS2Rs have been identified as responsible for recognizing numerous bitter compounds, showcasing their high structural diversity to bitter agonists. Thus, reducing bitterness can be achieved through several methods. Traditionally, the removal or degradation of bitter substances has been used for debittering, while the masking of bitterness presents a new effective approach to improving food flavor. Future research in food bitterness should focus on identifying unknown bitter compounds in food, elucidating the mechanisms of activation of different receptors, and developing debittering techniques based on the entire food matrix.

Comparative Analysis of Metabolic Variation in Eggplant Fruit of Different Varieties Reveals Metabolites Important for Quality Traits

Eggplant is one of the most important vegetable crops worldwide and has been considered to have great antioxidant activity. However, little information is available about the primary metabolic composition of the nutritional values of eggplant. Using a widely targeted metabolome approach, the current study investigated primary metabolic variation in 13 eggplant varieties with different morphologies. A total of 503 primary metabolites (amino acids, lipids, nucleotides, organic acids, vitamin, saccharides, and alcohols) and 170 phenolic acids were detected, among which 211 metabolites were differently accumulated. Metabolic pathway analysis of the differential metabolites revealed the significant enrichment of phenylpropanoid biosynthesis, arginine biosynthesis, alpha-linolenic acid metabolism, and linoleic acid metabolism. The higher levels of amino acids and lipids were related to the umami, soft, and waxy taste of eggplant fruit. The present work substantially contributes to the knowledge of primary metabolite compositions regarding fruit-eating quality and provides useful information for the future breeding of eggplant.

Dracocephalum jacutense Peschkova from Yakutia: Extraction and Mass Spectrometric Characterization of 128 Chemical Compounds

Dracocephalum jacutense Peschkova is a rare and endangered species of the genus Dracocephalum of the Lamiaceae family. The species was first described in 1997 and listed in the Red Data Book of Yakutia. Significant differences in the multicomponent composition of extracts from D. jacutense collected in the natural environment and successfully introduced in the Botanical Garden of Yakutsk were identified by a team of authors earlier in a large study. In this work, we studied the chemical composition of the leaves, stem, and inflorescences of D. jacutense using the tandem mass spectrometry method. Only three cenopopulations of D. jacutense were found by us in the territory of the early habitat-in the vicinity of the village of Sangar, Kobyaysky district of Yakutia. The aboveground phytomass of the plant was collected, processed and dried as separate parts of the plant: inflorescences, stem and leaves. Firstly, a total of 128 compounds, 70% of which are polyphenols, were tentatively identified in extracts of D. jacutense. These polyphenol compounds were classified as 32 flavones, 12 flavonols, 6 flavan-3-ols, 7 flavanones, 17 phenolic acids, 2 lignans, 1 dihydrochalcone, 4 coumarins, and 8 anthocyanidins. Other chemical groups were presented as carotenoids, omega-3-fatty acids, omega-5-fatty acids, amino acids, purines, alkaloids, and sterols. The inflorescences are the richest in polyphenols (73 polyphenolic compounds were identified), while 33 and 22 polyphenols were found in the leaves and stems, respectively. A high level of identity for polyphenolic compounds in different parts of the plant is noted for flavanones (80%), followed by flavonols (25%), phenolic acids (15%), and flavones (13%). Furthermore, 78 compounds were identified for the first time in representatives of the genus Dracocephalum, including 50 polyphenolic compounds and 28 compounds of other chemical groups. The obtained results testify to the unique composition of polyphenolic compounds in different parts of D. jacutense.

Combined analysis of the metabolome and transcriptome provides insight into seed oil accumulation in soybean

BACKGROUND

Soybean (Glycine max (L.) Merr) is an important source of human food, animal feed, and bio-energy. Although the genetic network of lipid metabolism is clear in Arabidopsis, the understanding of lipid metabolism in soybean is limited.

RESULTS

In this study, 30 soybean varieties were subjected to transcriptome and metabolome analysis. In total, 98 lipid-related metabolites were identified, including glycerophospholipid, alpha-linolenic acid, linoleic acid, glycolysis, pyruvate, and the sphingolipid pathway. Of these, glycerophospholipid pathway metabolites accounted for the majority of total lipids. Combining the transcriptomic and metabolomic analyses, we found that 33 lipid-related metabolites and 83 lipid-related genes, 14 lipid-related metabolites and 17 lipid-related genes, and 12 lipid-related metabolites and 25 lipid-related genes were significantly correlated in FHO (five high-oil varieties) vs. FLO (five low-oil varieties), THO (10 high-oil varieties) vs. TLO (10 low-oil varieties), and HO (15 high-oil varieties) vs. LO (15 low-oil varieties), respectively.

CONCLUSIONS

The GmGAPDH and GmGPAT genes were significantly correlated with lipid metabolism genes, and the result revealed the regulatory relationship between glycolysis and oil synthesis. These results improve our understanding of the regulatory mechanism of soybean seed oil improvement.

Special tea products featuring functional components: Health benefits and processing strategies

The functional components in tea confer various potential health benefits to humans. To date, several special tea products featuring functional components (STPFCs) have been successfully developed, such as O-methylated catechin-rich tea, γ-aminobutyric acid-rich tea, low-caffeine tea, and selenium-rich tea products. STPFCs have some unique and enhanced health benefits when compared with conventional tea products, which can meet the specific needs and preferences of different groups and have huge market potential. The processing strategies to improve the health benefits of tea products by regulating the functional component content have been an active area of research in food science. The fresh leaves of some specific tea varieties rich in functional components are used as raw materials, and special processing technologies are employed to prepare STPFCs. Huge progress has been achieved in the research and development of these STPFCs. However, the current status of these STPFCs has not yet been systematically reviewed. Here, studies on STPFCs have been comprehensively reviewed with a focus on their potential health benefits and processing strategies. Additionally, other chemical components with the potential to be developed into special teas and the application of tea functional components in the food industry have been discussed. Finally, suggestions on the promises and challenges for the future study of these STPFCs have been provided. This paper might shed light on the current status of the research and development of these STPFCs. Future studies on STPFCs should focus on screening specific tea varieties, identifying new functional components, evaluating health-promoting effects, improving flavor quality, and elucidating the interactions between functional components.

Identification and Analysis of Metabolites That Contribute to the Formation of Distinctive Flavour Components of Laoxianghuang

In addition to volatile compounds, metabolites also have a great effect on the flavour of food. Fresh finger citron cannot be eaten directly because of its spicy and bitter taste, so it is made into a preserved fruit product known as Laoxianghuang (LXH). To investigate the metabolites that have an effect on the flavour of LXH, untargeted metabolomics was performed using an ultrahigh-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS), and the metabolites of the Laoxianghuang samples from different locations in the Chaoshan area were compared and analysed. A total of 756 metabolites were identified and distinct differences were revealed among the different Laoxianghuang samples. A total of 33 differential metabolites with the most significant changes were screened through further multivariate analytical steps, and each group of samples had unique metabolites. For instance, pomolic acid had the highest content in the JG sample, while L-glycyl-L-isoleucine was rich in the QS sample. Moreover, flavonoid metabolites made the greatest contribution to the unique flavour of Laoxianghuang. The metabolic pathways involved are the biosynthetic pathways of flavonoids, isoflavonoids, flavones, and flavonols. This study can provide some creative information for distinguishing the quality differences of Laoxianghuang from the perspective of metabolites and offer preliminary theoretical support to characterise the formation of flavour substances in Laoxianghuang.

Autofluorescence-Based Investigation of Spatial Distribution of Phenolic Compounds in Soybeans Using Confocal Laser Microscopy and a High-Resolution Mass Spectrometric Approach

In this research, we present a detailed comparative analysis of the bioactive substances of soybean varieties k-11538 (Russia), k-11559 (Russia), k-569 (China), k-5367 (China), k-5373 (China), k-5586 (Sweden), and Primorskaya-86 (Russia) using an LSM 800 confocal laser microscope and an amaZon ion trap SL mass spectrometer. Laser microscopy made it possible to clarify in detail the spatial arrangement of the polyphenolic content of soybeans. Our results revealed that the phenolics of soybean are spatially located mainly in the seed coat and the outer layer of the cotyledon. High-performance liquid chromatography (HPLC) was used in combination with an amaZon SL BRUKER DALTONIKS ion trap (tandem mass spectrometry) to identify target analytes in soybean extracts. The results of initial studies revealed the presence of 63 compounds, and 45 of the target analytes were identified as polyphenolic compounds.

Identification and Spatial Distribution of Bioactive Compounds in Seeds Vigna unguiculata (L.) Walp. by Laser Microscopy and Tandem Mass Spectrometry

The research presents a comparative metabolomic study of extracts of Vigna unguiculata seed samples from the collection of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources. Analyzed samples related to different areas of use in agricultural production, belonging to different cultivar groups sesquipedalis (vegetable accessions) and unguiculata (grain accessions). Metabolome analysis was performed by liquid chromatography combined with ion trap mass spectrometry. Substances were localized in seeds using confocal and laser microscopy. As a result, 49 bioactive compounds were identified: flavonols, flavones, flavan-3-ols, anthocyanidin, phenolic acids, amino acids, monocarboxylic acids, aminobenzoic acids, fatty acids, lignans, carotenoid, sapogenins, steroids, etc. Steroidal alkaloids were identified in V. unguiculata seeds for the first time. The seed coat (palisade epidermis and parenchyma) is the richest in phenolic compounds. Comparison of seeds of varieties of different directions of use in terms of the number of bioactive substances identified revealed a significant superiority of vegetable accessions over grain ones in this indicator, 36 compounds were found in samples from cultivar group sesquipedalis, and 24 in unguiculata. The greatest variety of bioactive compounds was found in the vegetable accession k-640 from China.

Zostera marina L.: Supercritical CO2-Extraction and Mass Spectrometric Characterization of Chemical Constituents Recovered from Seagrass

Three types of Zostera marina L. collection were extracted using the supercritical CO2-extraction method. For the purposes of supercritical CO2-extraction, old seagrass ejection on the surf edge, fresh seagrass ejection on the surf edge and seagrass collected in water were used. Several experimental conditions were investigated in the pressure range 50–350 bar, with the used volume of co-solvent ethanol in the amount of 1% in the liquid phase at a temperature in the range of 31–70 °C. The most effective extraction conditions are: pressure 250 Bar and temperature 60 °C for Z. marina collected in sea water. Z. marina contain various phenolic compounds and sulfated polyphenols with valuable biological activity. Tandem mass-spectrometry (HPLC-ESI–ion trap) was applied to detect target analytes. 77 different biologically active components have been identified in Z. marina supercritical CO2-extracts. 38 polyphenols were identified for the first time in Z. marina.

UPLC-QQQ-MS/MS-based widely targeted metabolomic analysis reveals the effect of solid-state fermentation with Eurotium cristatum on the dynamic changes in the metabolite profile of dark tea

Eurotium cristatum is the predominant fungus and key contributor to the characteristics of post-fermented Fu brick tea (FBT) during manufacturing. In this study, the influence of solid-state fermentation (SSF) with E. cristatum on the chemical profile dynamic changes of dark tea was investigated. Results indicated that total phenolics, flavonoids, theaflavins, thearubigins, and galloyl catechins consistently decreased, degalloyl catechins and gallic acid increased in the initial stage of fermentation and decreased after long-term fermentation, and theabrownins continually increased. UPLC-QQQ-MS/MS-based widely targeted metabolomic analysis revealed that the metabolites of dark tea processed by SSF with E. cristatum were drastically different from the raw material. A total of 574 differential metabolites covering 11 subclasses were detected in the whole SSF of dark tea, and the most drastic changes occurred in the middle stage. Phenolic acids and flavonoids were the two major classes of differential metabolites. A series of reactions such as degradation, glycosylation, deglycosylation, methylation, and oxidative polymerization occurred during SSF. Overall, SSF with E. cristatum greatly influenced the metabolites of dark tea, which provided valuable insights that E. cristatum is critical in forming the chemical constituents of FBT.

Nontargeted and targeted metabolomics analysis provides novel insight into nonvolatile metabolites in Jianghua Kucha tea germplasm (Camellia sinensis var. Assamica cv. Jianghua)

Jianghua Kucha (JHKC) is a special tea germplasm with high bitterness growing in China; however, the chemical characteristics of JHKC are not completely understood. In this study, 61 differential metabolites were identified between 11 wild JHKC individuals and 3 control cultivars of Fudingdabai, Yunkang 10, and Zhuyeqi using comprehensive nontargeted and targeted metabolomics approach. The JHKC accessions mainly possessed significantly higher levels of purine alkaloids of theacrine (12.06 ± 5.23 mg/g) and 1,3,7-trimethyluric acid, non-epi-form flavanols (catechin, gallocatechin, catechin gallate, and gallocatechin gallate), and methylated flavanols of epigallocatechin-3-O-(3″-O-methyl)-gallate (4.79 ± 1.45 mg/g) and epicatechin-3-O-(3″-O-methyl)-gallate (1.02 ± 0.34 mg/g), as well as significantly lower levels of flavonol glycosides, which indicated that caffeine metabolism, flavonoid biosynthesis, and flavonol and flavone biosynthesis are mostly differential metabolic pathways. Our study demonstrated that JHKC germplasm is a promising resource for breeding novel tea cultivars with high contents of theacrine, non-epi-form flavanols, and methylated flavanols.

Discriminant Analysis of Pu-Erh Tea of Different Raw Materials Based on Phytochemicals Using Chemometrics

Pu-erh tea processed from the sun-dried green tea leaves can be divided into ancient tea (AT) and terrace tea (TT) according to the source of raw material. However, their similar appearance makes AT present low market identification, resulting in a disruption in the tea market rules of fair trade. Therefore, this study analyzed the classification by principal component analysis/hierarchical clustering analysis and conducted the discriminant model through stepwise Fisher discriminant analysis and decision tree analysis based on the contents of water extract, phenolic components, alkaloid, and amino acids, aiming to investigate whether phytochemicals coupled with chemometric analyses distinguish AT and TT. Results showed that there were good separations between AT and TT, which was caused by 16 components with significant (p < 0.05) differences. The discriminant model of AT and TT was established based on six discriminant variables including water extract, (+)-catechin, (−)-epicatechin, (−)-epigallocatechin, theacrine, and theanine. Among them, water extract comprised multiple soluble solids, representing the thickness of tea infusion. The model had good generalization capability with 100% of performance indexes according to scores of the training set and model set. In conclusion, phytochemicals coupled with chemometrics analyses are a good approach for the identification of different raw materials.

Spatial Distribution of Polyphenolic Compounds in Corn Grains (Zea mays L. var. Pioneer) Studied by Laser Confocal Microscopy and High-Resolution Mass Spectrometry

Desirable changes in the biochemical composition of food plants is a key outcome of breeding strategies. The subsequent localization of nutritional phytochemicals in plant tissues gives important information regarding the extent of their synthesis across a tissue. We performed a detailed metabolomic analysis of phytochemical substances of grains from Zea mays L. (var. Pioneer) by tandem mass spectrometry and localization by confocal microscopy. We found that anthocyanins are located mainly in the aleurone layer of the grain. High-performance liquid chromatography in combination with ion trap tandem mass spectrometry revealed the presence of 56 compounds, including 30 polyphenols. This method allows for effective and rapid analysis of anthocyanins by plotting their distribution in seeds and grains of different plants. This approach will permit a more efficient screening of phenotypic varieties during food plant breeding.

Dracocephalum palmatum S. and Dracocephalum ruyschiana L. Originating from Yakutia: A High-Resolution Mass Spectrometric Approach for the Comprehensive Characterization of Phenolic Compounds

Dracocephalum palmatum S. and Dracocephalum ruyschiana L. contain a large number of target analytes, which are biologically active compounds. High performance liquid chromatography (HPLC) in combination with an ion trap (tandem mass spectrometry) was used to identify target analytes in extracts of D. palmatum S. and D. ruyschiana L. originating from Yakutia. The results of initial studies revealed the presence of 114 compounds, of which 92 were identified for the first time in the genus Dracocephalum. New identified metabolites belonged to 17 classes, including 16 phenolic acids and their conjugates, 18 flavones, 5 flavonols, 2 flavan-3-ols, 1 flavanone, 2 stilbenes, 10 anthocyanins, 1 condensed tannin, 2 lignans, 6 carotenoids, 3 oxylipins, 2 amino acids, 3 sceletium alkaloids, 3 carboxylic acids, 8 fatty acids, 1 sterol, and 3 terpenes, along with 6 miscellaneous compounds. It was shown that extracts of D. palmatum are richer in the spectrum of polyphenolic compounds compared with extracts of D. ruyschiana, according to a study of the presence of these compounds in extracts, based on the results of mass spectrometric studies.

Research of Dracocephalum palmatum S. and Dracocephalum ruyschiana L. originating from Yakutia and identification of metabolites by tandem mass spectrometry

Dracocephalum palmatum Stephan and Dracocephalum ruyschiana L. contains a large number of target analytes, which are biologically active compounds. High performance liquid chromatography (HPLC) in combination with a BRUKER DALTONIKS ion trap (tandem mass spectrometry) was used to identify target analytes in extracts of D. palmatum Stephan and D. ruyschiana L., originating from Yakutia. The results of initial studies revealed the presence of 61 compounds, of which 53 were identified for the first time in genus Dracocephalum. These are flavones: Apigenin 8-C-pentoside-6-C-hexoside, Apigenin 7-sulfate; Chrysin 6-C-glucoside, Chrysin glucuronide; flavanols: Kaempferol, Dihydrokaempferol, Astragalin; flavan-3-ol (epi)Catechin, phenolic acids: Methylgallic acid; Hydroxy methoxy dimethylbenzoic acid; Ellagic acid; Caffeoylshikimic acid; Prolithospermic acid; 3,4-O-dicaffeoylquinic acid; salvianolic acid G; stilbenes pinosylvin and resveratrol; anthocyanins Petunidin, Pelargonidin-3-O-glucoside; Peonidin-3-O-glucoside; Cyanidin 3-(acetyl)hexose; perillic acid; lignans: Hinokinin, Dimethyl-secoisolariciresinol, Podophyllotoxin, carotenoids: Apocarotenal, 5,8-epoxy-alpha-carotene; etc.

Towards Higher Sensitivity of Mass Spectrometry: A Perspective From the Mass Analyzers

Mass spectrometry (MS) is one of the most widely used analytical techniques in many fields. Recent developments in chemical and biological researches have drawn much attention to the measurement of substances with low abundances in samples. Continuous efforts have been made consequently to further improve the sensitivity of MS. Modifications on the mass analyzers of mass spectrometers offer a direct, universal and practical way to obtain higher sensitivity. This review provides a comprehensive overview of the latest developments in mass analyzers for the improvement of mass spectrometers' sensitivity, including quadrupole, ion trap, time-of-flight (TOF) and Fourier transform ion cyclotron (FT-ICR), as well as different combinations of these mass analyzers. The advantages and limitations of different mass analyzers and their combinations are compared and discussed. This review provides guidance to the selection of suitable mass spectrometers in chemical and biological analytical applications. It is also beneficial to the development of novel mass spectrometers.

Identification of Co-Expressed Genes Related to Theacrine Synthesis in Tea Flowers at Different Developmental Stages

Jiaocheng kucha is the first reported tea germplasm resource which contains theacrine founded in Fujian Province. Currently, the anabolic mechanism of theacrine within tea leaves is clear, but there are few studies focused on its flowers. In order to further explore the mechanism of theacrine synthesis and related genes in flowers, current study applied Jiaocheng kucha flowers (JC) as test materials and Fuding Dabaicha flowers (FD) as control materials to make transcriptome sequencing, and determination of purine alkaloid content in three different developmental periods (flower bud stage, whitening stage and full opening stage). The results showed that the flower in all stages of JC contained theacrine. The theacrine in the flower bud stage was significantly higher than in the other stages. The differentially expressed genes (DEGs) at three different developmental stages were screened from the transcriptome data, and were in a total of 5642, 8640 and 8465. These DEGs related to the synthesis of theacrine were primarily annotated to the pathways of purine alkaloids. Among them, the number of DEGs in xanthine synthesis pathway was the largest and upregulated in JC, while it was the smallest in caffeine synthesis pathway and downregulated in JC. Further weighted gene co-expression network (WGCNA) indicated that ADSL (CsTGY03G0002327), ADSL (CsTGY09G0001824) and UAZ (CsTGY06G0002694) may be a hub gene for the regulation of theacrine metabolism in JC. Our results will contribute to the identification of candidate genes related to the synthesis of theacrine in tea flowers, and explore the molecular mechanism of theacrine synthesis in JC at different developmental stages.

Analysis of Differentiated Chemical Components between Zijuan Purple Tea and Yunkang Green Tea by UHPLC-Orbitrap-MS/MS Combined with Chemometrics

Zijuan tea (Camellia sinensis var. assamica cv. Zijuan) is a unique purple tea. Recently, purple tea has drawn much attention for its special flavor and health benefits. However, the characteristic compounds of purple tea compared with green tea have not been reported yet. The present study employed a non-targeted metabolomics approach based on ultra-high performance liquid chromatography (UHPLC)-Orbitrap-tandem mass spectrometry (MS/MS) for comprehensive analysis of characteristic metabolites between Zijuan purple tea (ZJT) and Yunkang green tea (YKT). Partial least squares-discriminant analysis (PLS-DA) indicated that there are significant differences in chemical profiles between ZJT and YKT. A total of 66 major differential metabolites included catechins, proanthocyanins, flavonol and flavone glycosides, phenolic acids, amino acids and alkaloids were identified in ZJT. Among them, anthocyanins are the most characteristic metabolites. Nine glycosides of anthocyanins and six glycosides of proanthocyanins were found to be significantly higher in ZJT than that in YKT. Subsequently, pathway analysis revealed that ZJT might generate anthocyanins and proanthocyanins through the flavonol and flavone glycosides. Furthermore, quantitative analysis showed absolutely higher concentrations of total anthocyanins in ZJT, which correlated with the metabolomics results. This study presented the comprehensive chemical profiling and the characterized metabolites of ZJT. These results also provided chemical evidence for potential health functions of ZJT.

Comprehensive identification of non-volatile bitter-tasting compounds in Zanthoxylum bungeanum Maxim. by untargeted metabolomics combined with sensory-guided fractionation technique

Zanthoxylum Bungeanum Maxim. is an important seasoning in Chinese cooking, but its bitter taste limits its use by some consumers. In this study, metabolomic analysis based on ultra-high-performance liquid chromatograph-tandem mass spectrometry (UPLC-MS) was used to screen out a vast number of potential non-volatile bitter compounds in Z. bungeanum. Results showed that there were 37 potential bitter compounds in Z. bungeanum, and possible mechanisms underlying its bitter taste were provided. Further, instrumental analyses combined with sensory evaluation were used to identify the key bitter compounds in Gou jiao, a wild variant of Z. Bungeanum with a strong bitter taste. Totally 15 key bitter compounds were identified, most of which have a low bitterness recognition threshold. This study is the first comprehensive identification of non-volatile bitter compounds in Z. bungeanum and provides a basis for future investigations into mitigating bitterness and uncovering how the interaction between different bitter compounds affects taste.