In vitro antioxidant and pancreatic α-amylase inhibitory activity of isolated fractions from water extract of Qingzhuan tea

LC-MS metabolomics and molecular docking approaches to identify antihyperglycemic and antioxidant compounds from Melastoma malabathricum L. Leaf

The dried leaves of Melastoma malabathricum L., locally named Karamunting or Senduduk, is traditionally consumed in many regions in Indonesia as herbal tea to cure different illnesses, including diabetes. To date, information on the compounds responsible for their antidiabetic activity is still very rare. The study aimed to identify bioactive compounds of M. malabathricum L. leaves using LC-MS based metabolomics and molecular docking approaches. The leaves brewed with different methods were subjected to LC-MS measurements and several bioactivity tests (in vivo and in vitro antihyperglycemic, and in vitro antioxidant). LC-MS data were linked to the activity data using multivariate data analysis. Molecular docking using alpha-glucosidase, alpha-amylase, and insulin receptor as protein targets was used to verify the results and study the interaction between the identified compound and protein targets. As results, isoquercetin and myricitrin were identified as compounds strongly associated with alpha-amylase inhibitors, while rutin and epicatechin were identified as alpha-glucosidase inhibitors. Quercitrin, citric acid, quercetin, epicatechin, isoquercitrin, and 7-hydroxycoumarine were strongly correlated with both antihyperglycemic and antioxidant activities. The results of metabolomics were confirmed with molecular docking studies, which showed that some of these compounds acted as competitive inhibitors, while others acted as non-competitive ones. Possible synergism between epicatechin and citric acid in their interaction with IR was detected. Metabolomics combined with molecular docking efficiently identified and confirmed several antihyperglycemic and antioxidant compounds from M. malabathricum L., leaf. This study provides scientific evidence for the traditional use of M. malabathricum L. as an antidiabetic herbal.

Heptaellipside A, a rare new 2,28-bidesmosidic lupane-type saponin from the leaves of Heptapleurum ellipticum

For the first time, phytochemical constituents of the leaves of Heptapleurum ellipticum were investigated. One rare new 2,28-bidesmosidic lupane-type saponin, named heptaellipside A (1), along with four other lupane-type analogs (2-5) were purified by combining differently chromatographic methods. All of the separated compounds (1-5) were communicated for the first time from H. ellipticum. The structures of them were definitely illustrated following extensive and comprehensive UV/VIS, FTIR, HRMS/ESI, and NMR techniques. Further, all isolated compounds were evaluated for their α-glucosidase and α-amylase inhibition. As the results, compound 3 respectively exhibited stronger in both inhibitory activities against α-glucosidase and α-amylase (IC50 values of 15.53 and 26.93 μM), than the acarbose standard (IC50 values of 214.50 and 143.48 μM).

Exploring core functional fungi driving the metabolic conversion in the industrial pile fermentation of Qingzhuan tea

The distinct sensory quality of Qingzhuan tea is mainly formed in pile fermentation by a group of functional microorganisms but the core functional ones was poorly characterized. Therefore, this study investigated the dynamic changes in the fungal community and metabolic profile by integrating microbiomics and metabolomics, and explored the core functional fungi driving the metabolic conversion in the industrial pile fermentation of Qingzhuan tea. Indicated by microbiomics analysis, Aspergillus dominated the entire pile-fermentation process, while Thermoascus, Rasamsonia, and Cylindrium successively abounded in the different stages of the pile fermentation. A total of 50 differentially changed metabolites were identified, with the hydrolysis of galloyl/polymeric catechins, biosynthesis of theabrownins, oxidation of catechins, N-ethyl-2-pyrrolidinone substitution of catechins, and deglycosylation of flavonoid glucosides. Nine fungal genera were identified as core functional fungi, in which Aspergillus linked to the hydrolysis of polymeric catechins and insoluble polysaccharides as well as biosynthesis of theabrownins, while Thermoascus participated in the biosynthesis of theabrownins, deglycosylation of flavonoid glucosides, and N-ethyl-2-pyrrolidinone substitution of catechins. These findings would advance our understanding of the quality formation of Qingzhuan tea and provide a benchmark for precise inoculation for its quality improvement.

Genome-wide characterization of COMT family and regulatory role of CsCOMT19 in melatonin synthesis in Camellia sinensis

BACKGROUND

Caffeic acid O-methyltransferase (COMT) is a key enzyme that regulates melatonin synthesis and is involved in regulating the growth, development, and response to abiotic stress in plants. Tea plant is a popular beverage consumed worldwide, has been used for centuries for its medicinal properties, including its ability to reduce inflammation, improve digestion, and boost immune function. By analyzing genetic variation within the COMT family, while helping tea plants resist adversity, it is also possible to gain a deeper understanding of how different tea varieties produce and metabolize catechins, then be used to develop new tea cultivars with desired flavor profiles and health benefits.

RESULTS

In this study, a total of 25 CsCOMT genes were identified based on the high-quality tea (Camellia sinensis) plant genome database. Phylogenetic tree analysis of CsCOMTs with COMTs from other species showed that COMTs divided into four subfamilies (Class I, II, III, IV), and CsCOMTs was distributed in Class I, Class II, Class III. CsCOMTs not only undergoes large-scale gene recombination in pairs internally in tea plant, but also shares 2 and 7 collinear genes with Arabidopsis thaliana and poplar (Populus trichocarpa), respectively. The promoter region of CsCOMTs was found to be rich in cis-acting elements associated with plant growth and stress response. By analyzing the previously transcriptome data, it was found that some members of CsCOMT family exhibited significant tissue-specific expression and differential expression under different stress treatments. Subsequently, we selected six CsCOMTs to further validated their expression levels in different tissues organ using qRT-PCR. In addition, we silenced the CsCOMT19 through virus-induced gene silencing (VIGS) method and found that CsCOMT19 positively regulates the synthesis of melatonin in tea plant.

CONCLUSION

These results will contribute to the understanding the functions of CsCOMT gene family and provide valuable information for further research on the role of CsCOMT genes in regulating tea plant growth, development, and response to abiotic stress.

Chemical Analysis of the Antihyperglycemic, and Pancreatic α-Amylase, Lipase, and Intestinal α-Glucosidase Inhibitory Activities of Cannabis sativa L. Seed Extracts

Cannabis is considered (Cannabis sativa L.) a sacred herb in many countries and is vastly employed in traditional medicine to remedy numerous diseases, such as diabetes. This research investigates the chemical composition of the aqueous extracts from Cannabis sativa L. seeds. Furthermore, the impact of these extracts on pancreatic α-amylase and lipase, and intestinal α-glucosidase enzymes is evaluated, as well as their antihyperglycemic effect. Analysis of the chemical composition of the aqueous extract was conducted using high-performance liquid chromatography with a photodiode array detector (HPLC-DAD). In contrast, the ethanol, hexanic, dichloromethane, and aqueous extract compositions have been established. Additionally, the inhibitory effects of ethanolic, dichloromethane, and aqueous extracts on pancreatic α-amylase and lipase, and intestinal α-glucosidase activities were evaluated in vitro and in vivo. The results of HPLC analysis indicate that the most abundant phenolic compound in the aqueous cannabis seed extract is 3-hydroxycinnamic acid, followed by 4-hydroxybenzoic acid and rutin acid. Moreover, administration of ethanolic and aqueous extracts at a dose of 150 mg/Kg significantly suppressed postprandial hyperglycemia compared to the control group; the ethanolic, dichloromethane, and aqueous extracts significantly inhibit pancreatic α-amylase and lipase, and intestinal α-glucosidase in vitro. The pancreatic α-amylase test exhibited an inhibition with IC50 values of 16.36 ± 1.24 µg/mL, 19.33 ± 1.40 µg/mL, 23.53 ± 1.70 µg/mL, and 17.06 ± 9.91 µg/mL for EAq, EDm, EET, and EHx, respectively. EET has the highest inhibitory capacity for intestinal α-glucosidase activity, with an IC50 of 32.23 ± 3.26 µg/mL. The extracts inhibit porcine pancreatic lipase activity, demonstrating their potential as lipase inhibitors. Specifically, at a concentration of 1 mg/mL, the highest inhibition rate (77%) was observed for EDm. To confirm these results, the inhibitory effect of these extracts on enzymes was tested in vivo. The oral intake of aqueous extract markedly reduced starch- and sucrose-induced hyperglycemia in healthy rats. Administration of the ethanolic extract at a specific dose of 150 mg/kg significantly reduced postprandial glycemia compared with the control group. It is, therefore, undeniable that cannabis extracts represent a promising option as a potentially effective treatment for type 2 diabetes.

Metabolomic and transcriptomic analyses reveal comparisons against liquid-state fermentation of primary dark tea, green tea and white tea by Aspergillus cristatus

Liquid-state fermentation (LSF) of tea leaves is a promising way to obtain tea-based nutraceutical products rich in various bioactive compounds. In the study, the changes of bioactive compounds, tea pigments and complex metabolites from LSF of primary dark tea, green tea and white tea infusions with Aspergillus cristatus were determined. Chemical analyses revealed that soluble sugars, monosaccharide composition, total polyphenols, total flavonoids, free amino acids, soluble proteins and tea pigments were changed in different ways. An untargeted metabolomic analysis and ribonucleic acid sequencing (RNA-seq) based transcriptomic analysis were performed to investigate the metabolic differentiation and clarify the key differentially expressed genes (DEGs, fold change >2 and p < 0.05), showing that amino acid metabolism, carbohydrate metabolism and lipid metabolism were the most enriched pathways during A. cristatus fermentation of primary dark tea, green tea and white tea infusions. In addition, glycerophospholipid metabolism, linoleic acid metabolism and phenylalanine metabolism were greatly accumulated in the fermentation of primary dark tea and white tea infusions; Pyruvate metabolism, glycolysis/gluconeogenesis, fatty acid degradation, tyrosine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis and valine and leucine, isoleucine degradation were greatly accumulated in the fermentation of primary dark tea and green tea infusions; Starch and sucrose metabolism was greatly accumulated in the fermentation of green tea and white tea infusions; Galactose metabolism was significantly enhanced in the fermentation of primary dark tea infusion; Amino sugar and nucleotide sugar metabolism, sphingolipid metabolism and alanine, aspartate and glutamate metabolism were significantly enhanced in the fermentation of green tea infusion. Besides, some other pathways involving aminobenzoate degradation, biosynthesis of cofactors, pyrimidine metabolism, benzoxazinoid biosynthesis and phenazine biosynthesis, tropane, piperidine and pyridine alkaloid biosynthesis and flavone and flavonol biosynthesis also differed from each other. These findings support that A. cristatus plays a vital role in the biochemical and genetic regulation of metabolite profile, and could be considered a potential prospect for better use of A. cristatus on different kinds of tea materials.

Structure-activity relationships and the underlying mechanism of α-amylase inhibition by hyperoside and quercetin: Multi-spectroscopy and molecular docking analyses

Inhibiting the activity of α-amylase has been considered an effective strategy to manage hyperglycemia. Hyperoside and quercetin are the main natural flavonoids in various plants, and the inhibition mechanism on α-amylase remains unclear. In this study, the structure-activity relationships between hyperoside/quercetin and α-amylase were evaluated by enzyme kinetic analysis, multi-spectroscopic techniques, and molecular docking analysis. Results showed that hyperoside and quercetin exhibited significant α-amylase inhibitory activities with IC₅₀ values of 0.491 and 0.325 mg/mL, respectively. The α-amylase activity decreased in the presence of hyperoside and quercetin in a competitive and noncompetitive manner, respectively. UV-vis spectra suggested that the aromatic amino acid residues (Trp and Tyr) microenvironment of α-amylase changed in the presence of these two flavonoids. FTIR and CD spectra showed the vibrations of the amide bands and the secondary structure content changes. The fluorescence quenching mechanism of α-amylase by hyperoside and quercetin belonged to the static quenching type. Finally, molecular docking intuitively showed that hyperoside/quercetin formed hydrogen bonds with the key active site residues (Asp197, Glu233, and Asp300) in α-amylase. MD simulation indicated hyperoside/quercetin-α-amylase docked complexes had good stability. Taken together, this research provides new sights to developing potent drugs or functional foods with hyperoside and quercetin, offering new avenues for hyperglycemia treatment.

The determination of monosaccharide in different years Qingzhuan Dark Tea polysaccharide by liquid chromatography-mass spectrometry

AIM

To establish a fast, sensitive and accurate high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for determining the monosaccharide content of Qingzhuan Dark Tea polysaccharides in different years (2 years, 5 years and 11 years).

METHODS

The optimised chromatographic conditions were achieved on a C18 column (5.0 μm, 250 mm × 4.6 mm inner diameter). The mobile phase flow rate was 0.9 mL/min and the column temperature was set to 27°C. The aqueous phase A (5 mM aqueous ammonium acetate) and organic phase B (acetonitrile) were used to elute the target analyses isocratically (0-60 min: 18% B). The mass spectrometer detector was equipped with an electron spray ionisation (ESI)source, and multiple reaction monitoring (MRM) mode was used for the determination of 1-phenyl-3-methyl-5-pyrazolone (PMP) derived monosaccharides.

RESULTS

We carried out a comprehensive methodological validation of PMP derived monosaccharides, including linearity, precision, stability and repeatability. Nine monosaccharides (rhamnose, mannose, ribose, glucose, galacturonic acid, xylose, galactose, fucose and arabinose) of Qingzhuan Dark Tea polysaccharides were identified, in which ribose and fucose were reported for the first time. The results showed the contents of these nine monosaccharides differed significantly among different years.

CONCLUSIONS

The validated method is reliable, accurate, repeatable and can be applied to quality assessment of these monosaccharides.

Enhancement in Seed Priming-Induced Starch Degradation of Rice Seed Under Chilling Stress via GA-Mediated α-Amylase Expression

Chilling stress is the major abiotic stress that severely limited the seedling establishment of direct-seeded rice in temperate and sub-tropical rice production regions. While seed priming is an efficient pre-sowing seed treatment in enhancing crop establishment under abiotic stress. Our previous research has identified two seed priming treatments, selenium priming (Se) and salicylic priming (SA) that effectively improved the seed germination and seedling growth of rice under chilling stress. To further explore how seed priming enhance the starch degradation of rice seeds under chilling stress, the present study evaluated the effects of Se and SA priming on germination and seedling growth, α-amylase activity, total soluble sugar content, hormone content and associated gene relative expression under chilling stress. The results showed that both Se and SA priming significantly increased the seed germination and seedling growth attributes, and enhanced the starch degradation ability by increasing α-amylase activity and total soluble sugar content under chilling stress. Meanwhile, seed priming increased the transcription level of OsRamy1A, OsRamy3B that regulated by GA, and increased the transcription level of OsRamy3E that regulated by sugar signals. Furthermore, seed priming significantly improved the GA₃ contents in rice seeds by up-regulating the expression of OsGA3ox1 and OsGA20ox1, and decreased the ABA content and the expression of OsNCED1, indicating that the improved starch degradation ability in primed rice seeds under chilling stress might be attributed to the increased GA₃ and decreased ABA levels in primed rice seeds, which induced the expression of GA-mediated α-amylase. However, studies to explore how seed priming mediate hormonal metabolism and the expression of OsRamy3E are desperately needed.

Untargeted Metabolomics Combined with Bioassay Reveals the Change in Critical Bioactive Compounds during the Processing of Qingzhuan Tea

Qingzhuan tea (QZT) is a typical Chinese dark tea that has a long-time manufacturing process. In the present study, liquid chromatography coupled with tandem mass spectrometry was used to study the chemical changes of tea samples during QZT processing. Untargeted metabolomics analysis revealed that the pile-fermentation and turnover (post-fermentation, FT) was the crucial stage in transforming the main compounds of QZT, whose contents of flavan-3-ols and flavonoids glycosides were decreased significantly. The bioactivities, including the antioxidant capacities and inhibitory effects on α-amylase and α-glucosidase, were also reduced after the FT process. It was suggested that although the QZT sensory properties improved following pile-fermentation and aging, the bioactivities remained restrained. Correlation analysis indicated that the main galloylated catechins and flavonoid glycosides were highly related to their antioxidant capacity and inhibitory effects on α-amylase and α-glucosidase.

Application of BRAFO-tiered approach for health benefit-risk assessment of dark tea consumption in China

Dark tea, a unique tea fermented primarily in China, has numerous potential beneficial effects. However, harmful substances present in dark tea have provoked significant concern. To conduct a quantitative benefit-risk assessment of dark tea for Chinese residents and provide guidance on rational consumption, a framework of Benefit-Risk Analysis for Foods (BRAFO) and meta-analysis was applied to construct a disability-adjusted life year (DALY). Based on the BRAFO-tiered approach, a reference scenario (no intake) and an alternative scenario (intake of 3 cups/day) were determined. The overall health impacts of dark tea were simulated by comparing the risks of fluoride and AF with benefits of reduced-risk to coronary heart disease (CHD) and diabetes in different scenarios. Three cups of fermented tea consumed per day decreased risks of CHD and diabetes by 8.16% and 12.77% respectively. After quantitative integration of information, the ultimate net health effect was found to be -1958.827 illustrating that the benefits of drinking three cups of dark tea per day outweigh the risks. However, considering the uncertainties in the process, decision-makers should proceed with caution, consulting additional well-conducted studies and further managing harmful substances in dark tea.

Comparative Metagenomics Reveals Microbial Communities and Their Associated Functions in Two Types of Fuzhuan Brick Tea

Fuzhuan brick tea (FBT) is a unique post-fermented tea product, naturally co-fermented by microorganisms, and has gained global popularity due to its potential health benefits for humans. Considerable efforts have been made toward elucidating the microbial diversity within FBT, but an understanding of the underlying FBT community interactions and functions remains poorly studied. Consequently, the microbial communities of two types of FBT, originating from Hunan and Shaanxi provinces, were investigated using comparative shotgun metagenomic sequencing and functional annotations. Metagenomic analysis indicated that two communities shared similar taxonomic and functional attributes. Two samples shared 486 genera, in which Pseudomonas contributed most to the abundant functions within the two samples. The carbohydrate active enzyme functions of the communities primarily comprised GH (32.92%), GT (26.8%), CEs (20.43%), and AAs (18.04%). Furthermore, the overall metabolic pathways encoded by the metagenomes were largely associated with carbohydrate and amino acid metabolism, with nine metabolic pathways that were differential between two groups including penicillin and cephalosporin biosynthesis. Significantly, a total of 35 potential probiotics were inferred, with Pseudomonas putida being the most abundant inferred probiotic (80%) within the FBT communities. This study provides new insights into FBT microbial communities on their potential functions and roles in FBT characteristics.

Changes of fungal community and non-volatile metabolites during pile-fermentation of dark green tea

Fungal community and non-volatile metabolites changes during the pile-fermentation are key factors to organoleptic qualities of dark green tea. However, the correlation between fungal succession and non-volatile compounds has never been satisfactorily explained. The purpose of the present study was to investigate fungal succession and its correlation with flavor compounds by multi-omics. Illumina Miseq sequencing of ITS1 region was conducted to analyze the fungal succession, a total of 78 OTUs which consisted of one phyla, nine classes, 15 orders, 26 families, 37 genera were identified, with Ascomycota as dominant phyla. Cluster analysis and non-metric multidimensional scaling of samples demonstrated the distribution of OTUs in multi-dimensional space, the pile-fermentation process of dark green tea can be divided into four periods according to the generated trajectory of fungal population, S0, S1-S3, S4-S5, and S6. Aspergillus is the dominant genus. Penicillium, Cyberlindnera, Debaryomyces, Candida, Thermomyces, Rasamsonia, Thermoascus, and Byssochlamys appear in different periods. three alkaloids, seven catechins, nine amino acids, five organic acids, five flavones and flavonoid glycosides were identified by UPLC-QTOF-MS/MS, and the contents were all decreasing. Caffeine, EGC, EGCG, L-theanine, kaempferitrin, L-phenylalanine, gallic acid, and myricetin-3-O-galactoside are important ingredients which contribute to the flavor of dark green tea. This study demonstrated the fungal succession, non-volatile flavor compounds and their relationships during pile-fermentation of dark green tea, and provides new insights into evaluating pivotal role of fungal succession in the manufacturing process of dark green tea.

Impact of Various Microbial-Fermented Methods on the Chemical Profile of Dark Tea Using a Single Raw Tea Material

In the present study, we produced Pu-erh, Liubao, Qingzhuan, and Fuzhuan teas using a single raw tea material and applied widely targeted metabolomics to study the impact of various microbial-fermented methods on the chemical profile of dark tea. The contents of catechins and free amino acids decreased drastically, whereas the contents of gallic acid and theabrownins increased significantly during microbial fermentation. Pu-erh tea had the highest content of theabrownins (11.82 ± 0.49%). Moreover, MS-based metabolomics analysis revealed that the different types of dark teas were significantly different from their raw material. A total of 85 differential metabolites were screened among 569 metabolites identified referring to self-compiled database. Glycosylated, hydroxylated, methylated, and condensed and oxidated products originating from microbial bioconversion of their corresponding primitive forms were significantly increased in dark teas. These results suggest that various microbial-fermented methods greatly affect the metabolic profile of dark tea, which can provide useful information for dark tea biochemistry research.

Hydroxycinnamic Acid from Corncob and Its Structural Analogues Inhibit Aβ40 Fibrillation and Attenuate Aβ40-Induced Cytotoxicity

The aggregation of amyloid-β protein (Aβ) is deemed a vital pathological feature of Alzheimer's disease (AD). Hence, inhibiting Aβ aggregation is noticed as a major tactic for the prevention and therapy of AD. Hydroxycinnamic acid, as a natural phenolic compound, is widely present in plant foods and has several biological activities including anti-inflammation, antioxidation, and neuroprotective effects. Here, it was found that hydroxycinnamic acid and its structural analogues (3-hydroxycinnamic acid, 2-hydroxycinnamic acid, cinnamic acid, 3,4-dihydroxycinnamic acid, 2,4-dihydroxycinnamic acid, and 3,4,5-trihydroxycinnamic acid) could inhibit Aβ40 fibrillogenesis and reduce Aβ40-induced cytotoxicity in a dose-dependent manner. Among these small molecules investigated, 3,4,5-trihydroxycinnamic acid is considered to be the most effective inhibitor, which reduces the ThT fluorescence intensity to 30.79% and increases cell viability from 49.47 to 84.78% at 200 μM. Also, the results with Caenorhabditis elegans verified that these small molecules can ameliorate AD-like symptoms of worm paralysis. Moreover, molecular docking studies showed that these small molecules interact with the Aβ40 mainly via hydrogen bonding. These results suggest that hydroxycinnamic acid and its structural analogues could inhibit Aβ40 fibrillogenesis and the inhibition activity is enhanced with the increase of phenolic hydroxyl groups of inhibitors. These small molecules have huge potential to be developed into novel aggregation inhibitors in neurodegenerative disorders.

Determination of six groups of mycotoxins in Chinese dark tea and the associated risk assessment

Chinese dark tea is widely enjoyed for its multiple health-promoting effects and pleasant taste. However, its production involves fermentation by microbiota in raw tea, some of which are filamentous fungi and thus potential mycotoxin producers. Accordingly, whether mycotoxins pose health risk on dark tea consumption has become a public concern. In this study, a cleaning method of multi-functional column (MFC) and immunoaffinity column (IAC) in tandem combined to HPLC detection was developed and validated for determining ten mycotoxins of six groups (i.e., aflatoxins of B₁, B₂, G₁ and G₂, ochratoxin A, zearalenone, deoxynivalenol, fumonisins of B₁, B₂, and T-2) in dark teas. The interferences from secondary metabolites were effectively reduced, and the sensitivities and recoveries of the method were qualified for tea matrices. Six groups mycotoxins were determined in 108 samples representing the major Chinese dark teas by using the new method. Subsequently, the dietary exposure and health risks were evaluated for different age and gender groups in Kunming and Pu'er in China and Ulan Bator in Mongolia. The occurrence of zearalenone was 4.63% and that of ochratoxin A was 1.85%, with the other four groups mycotoxins were below the limits of quantification. The hazard index values for the five groups' non-carcinogenic mycotoxins were far below 1.0. The deterministic risk assessment indicated no non-carcinogenic risks for dark tea consumption in the three areas. Probabilistic estimation showed that the maximum value of 95th percentile carcinogenic risk value for the aflatoxins was 2.12 × 10^-8, which is far below the acceptable carcinogenic risk level (10^-6). Hereby, six groups mycotoxins in Chinese dark tea showed no observed risk concern to consumers.

Carbohydrate digestive enzymes are inhibited by Poincianella pluviosa stem bark extract: relevance on type 2 diabetes treatment

Background

The stem bark aqueous alcohol extract of Poincianella pluviosa (PPSB extract) is rich in bioactives including gallic acid, gallic acid methyl ester, pyrogallol, ellagic acid, corilagin, 1,4,6-tri-O-galloyl-glucose, 1,2,3,6-tetra-O-galloyl-glucose, 1,2,3,4,6-penta-O-galloyl-glucose, tellimagrandin I, tellimagrandin II, mallotinic acid, mallotusinic acid, and geraniin. The aim of the present study was to evaluate the antioxidant activity of the PPSB extract as well as its inhibitory action on carbohydrate digestive enzymes relevant to type 2 diabetes.

Results

The PPSB extract was prepared using a mixture of 40% ethanol and 60% distilled water. The PPSB extract showed high antioxidant activities and inhibited several carbohydrate digestive enzymes. The IC50 values for inhibiting in vitro salivary amylase, pancreatic amylase, intestinal β-galactosidase and intestinal invertase were, respectively, 250 ± 15, 750 ± 40, 25 ± 5, and 75 ± 8 μg/mL. In vivo inhibition of the intestinal starch absorption was confirmed by determination of blood glucose levels in rats before and after administration of starch by gavage with or without different amounts of PPSB extract. Docking simulations performed on three different programs to rank the extract compounds most likely to bind to porcine pancreatic α-amylase suggest that geraniin is likely to be the P. pluviosa extract compound that presents the greatest binding potential to the pancreatic alpha-amylase. However, the total inhibitory action of the PPSB extract is likely to result from a summation of effects of several molecules. Furthermore, the PPSB extract did not present acute toxicity nor did it present mutagenic effects.

Conclusion

It can be concluded that the PPSB extract is potentially useful in controlling the postprandial glycaemic levels in diabetes. Further clinical studies with the extract are needed, however, to confirm its potential use in the management of type 2 diabetes.

Distinct Changes of Metabolic Profile and Sensory Quality during Qingzhuan Tea Processing Revealed by LC-MS-Based Metabolomics

Qingzhuan tea (QZT) is a unique type of dark tea exclusively produced in Hubei Province of China. In the current study, liquid chromatography-mass spectrometry (LC-MS) coupled with multivariate analysis was applied to characterize the chemical composition of QZT and investigate the effect of QZT processing on its metabolic profile and sensory quality. The contents of polyphenols and flavonoids decreased significantly while the polysaccharides content remained stable, while the theabrownin content inversely increased during QZT processing. LC-MS-based metabolomics analyses revealed that the tea sample after microbial fermentation (MFT) was dramatically different from the sample before microbial fermentation (UFT), while MFT was very similar to QZT. A total of 102 compounds were identified as critical metabolites responsible for metabolic changes caused by QZT processing, with the contents of catechins and flavonoids significantly decreased, and some novel phenolic acids and catechin derivatives were formed. The sensory quality of QZT was mainly formed during microbial fermentation, which greatly reduced the astringency and bitterness of raw tea leaves and produced its characteristic woody and stale aroma as well as mellow taste. These results suggested that microbial fermentation is the critical process in changing the metabolic profile of raw tea leaves and forming the sensory quality of QZT.

Effects of Cooking Methods and Tea Marinades on the Formation of Heterocyclic Amines and Benzo[a]pyrene in Grilled Drumsticks

ABSTRACT

The effects of different grilling methods and tea marinades on the formation of heterocyclic amines (HCAs) and benzo[a]pyrene (BaP) in grilled chicken drumsticks were investigated. This study showed that both the grilling method and type of charcoal used in charcoal grilling had a significant effect on the formation of HCAs and BaP. The total content of HCAs and BaP detected in drumsticks was the lowest under electric roasting, at 7.25 and 0.04 ng/g, respectively; thus, the electric grill can be used as an alternative grilling method to meet consumer demands for safety. The free radical scavenging ability of tea infusion was significantly higher than that of spice infusion. The white tea marinade significantly increased radical scavenging activity and prevented formation of HCAs and BaP more than the green tea marinade; thus, tea marinade can be applied to flavoring as a pretreatment to preserve the quality of meat and to decrease the generation of HCAs and BaP during cooking.

HIGHLIGHTS

Simultaneous Determination of Four Aflatoxins in Dark Tea by Multifunctional Purification Column and Immunoaffinity Column Coupled to Liquid Chromatography Tandem Mass Spectrometry

Dry tea matrix contains an abundance of caffeine and polyphenols which are different from the food matrix (e.g., protein, lipid, and carbohydrates), and only a few studies have tried aflatoxins determination with tea samples. Here, a specific, accurate, and sensitive method was developed and validated for the simultaneous determination of aflatoxin B1, B2, G1, and G2 in dark teas. Aflatoxins were extracted by acetonitrile/water, press-filtered, and cleaned by multifunctional purification column (MFC) and immunoaffinity column (IAC) in tandem. The cleaned extract was analyzed by liquid chromatography tandem mass spectrometry. The matrix interference was effectively reduced by MFC-IAC cleaning method. Recoveries at the spiking concentrations of 5-60 μg/kg ranged from 77.5 to 93%, with relative standard deviations <11.0%. The correlation coefficients of aflatoxins standard were >0.998. The limits of detection were 0.024-0.21 μg/kg and the limits of quantification were 0.08-0.74 μg/kg. The intra- and interday accuracy ranged from 74 to 87%, and the intra- and interday precisions ranged from 0.4 to 3.1%. After the method validation, the aflatoxins contaminations in 100 collected dark teas were detected, and the results were compared with those of other methods.

Consumption of post-fermented Jing-Wei Fuzhuan brick tea alleviates liver dysfunction and intestinal microbiota dysbiosis in high fructose diet-fed mice

Emerging evidence supports the health-promoting ability of a special microbial-fermented Fuzhuan brick tea. Epigallocatechin gallate was identified as a dominant flavonoid of Fuzhuan tea aqueous extract (FTE). Mice were treated with 30% high fructose (HF) water feeding alone or in combination with administration of FTE at 400 mg per kg bw for 13 weeks. FTE caused strong inhibition against the elevation of liver weight, serum enzymatic (aspartate aminotransferase, aspartate aminotransferase and alkaline phosphatase) activities and hepatic inflammatory cytokines (interleukin-1, interleukin-6, tumor necrosis factor-α and tumor necrosis factor-β) formation, as well as dyslipidemia (total cholesterol, total triglyceride, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol) in HF-fed mice (p < 0.05). Hepatic malonaldehyde formation was lowered, while superoxide dismutase and glutathione peroxidase activities were enhanced by FTE treatment, relative to HF-fed mice (p < 0.05), and histopathological evaluation confirmed the protection. As revealed by 16S rDNA gene sequencing, FTE notably increased abundance of Bacteroidetes and Lactobacillus, but reduced population of Firmicutes, Proteobacteria and Tenericutes in HF feeding mice. These findings suggest that FTE exerts a hepatoprotective effect by modifying hepatic oxidative stress, inflammatory response and gut microbiota dysfunction.

Fuzhuan brick tea can improve non-alcoholic fatty liver disease (NAFLD) and intestinal microbiota imbalance induced by a high fructose diet (HFD) intake in mice.

Animal study of the anti-diarrhea effect and microbial diversity of dark tea produced by the Yao population of Guangxi

Chinese dark teas (CDTs) are a special type of tea traditionally consumed by ethnic minorities around the border regions of China.

Dark tea extract mitigates hematopoietic radiation injury with antioxidative activity

The hematopoietic system is widely studied in radiation research. Tea has been proved to have antioxidative activity. In the present study, we describe the protective effects of dark tea extract (DTE) on radiation-induced hematopoietic injury. DTE administration significantly enhanced the survival rate of mice after 7.0 and 7.5 Gy total body irradiation (TBI). The results showed that DTE not only markedly increased the numbers and cloning potential of hematopoietic cells, but also decreased DNA damages after mice were exposed to 6.0 Gy total body irradiation (TBI). In addition, DTE also decreased the levels of reactive oxygen species (ROS) in hematopoietic cells by inhibiting NOX4 expression and increasing the dismutase, catalase and glutathione peroxidase in livers. These data demonstrate that DTE can prevent radiation-induced hematopoietic syndromes, which is beneficial for protection from radiation injuries.

Qing brick tea (QBT) aqueous extract protects monosodium glutamate-induced obese mice against metabolic syndrome and involves up-regulation Transcription Factor Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2) antioxidant pathway

BACKGROUND

Qing brick tea (QBT), traditional and popular beverage for Chinese people, is an important post-fermentation dark tea. Our present study was performed to investigate the ameliorative effects of QBT aqueous extract on metabolic syndrome (Mets) in monosodium glutamate-induced obese mice and the potential mechanisms.

METHOD

Monosodium glutamate-induced obese mice were used to evaluate the anti-Mets effects of QBT. Content levels of malonaldehyde (MDA), reactive oxygen species (ROS) and protein carbonylation, antioxidant enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione reductase (GR) in the skeletal muscle were assessed by commercial kits, respectively. Western blot and Q-PCR were used to detect the expressions of Transcription Factor Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2) signaling pathway and downstream antioxidant factors. In addition, activity of AKT signaling and expression of glucose transporter type 4 (GLUT4) in the skeletal muscle were investigated by western blot.

RESULT

QBT treatment limited gain of body weight, waistline and LEE index, improved insulin resistance and glucose intolerance, reduced lipid level in MSG mice. Content levels of MDA, ROS and protein carbonylation in skeletal muscle of QBT group were significantly improved compared to those of MSG mice. The antioxidant enzyme activities of SOD, GPx, CAT, and GR were increased in skeletal muscle of MSG mice intervened with QBT. After 20-week QBT treatment, Nrf2 signaling pathway and downstream antioxidant factors were both increased in the skeletal muscle. In addition, QBT treatment improved insulin signaling by preferentially augmenting AKT signaling, as well as increased the protein expression of GLUT4 in the skeletal muscle.

CONCLUSION

Our results showed that QBT intake was effective in protecting monosodium glutamate-induced obese mice against metabolic syndrome and involved in the Nrf2 signaling pathway in the skeletal muscle.

Structural characterization and evaluation of the antioxidant activities of polysaccharides extracted from Qingzhuan brick tea

The crude tea polysaccharides (CTPS) from Qingzhuan brick tea(QZBT) were extracted and fractionated to afford two fractions, namely TPS-1 and TPS-2. Analyses were conducted concerning the structural characterization and antioxidant activities of these samples. Component analysis revealed that the carbohydrate, uronic acid, protein and polyphenol contents of these samples differed significantly. Fourier transform infrared analysis showed that these samples showed similar characteristic absorption peaks for polysaccharides. Ultraviolet-visible spectroscopy, circular dichroism, scanning electron microscopy and thermogravimetric analyses indicated that there were considerable differences in the presence of protein, surface features, conformational characteristics and thermodynamic behaviors. For antioxidant activities in vitro, CTPS, TPS-1 and TPS-2 exhibited concentration-dependent antioxidant activities, with TPS-2 showing significantly higher antioxidant activity than CTPS and TPS-1. These results provide a scientific and strong foundation for the use of tea polysaccharides(TPS) from QZBT and further research towards the relationships between the characteristics and antioxidant activities of TPS.

Structural characterization and bioactivity of proanthocyanidins from indigenous cinnamon (Cinnamomum osmophloeum)

BACKGROUND

Barks and twigs of common species of cinnamon with abundant proanthocyanidins are used as a spice, fold medicine or supplement. Cinnamomum osmophloeum is an endemic species in Taiwan and coumarin was not detected in the oil of the C. osmophloeum twig. The present study aimed to evaluate the relationship between the bioactivities and proanthocyanidins of C. osmophloeum twig extracts (CoTE). The n-butanol soluble fraction from CoTE was divided into 10 subfractions (F1-F10) by Sephadex LH-20 gel chromatography. The antihyperglycemic activities were examined by α-glucosidase, α-amylase and protein tyrosine phosphatase 1B inhibitory assays. Total antioxidant activities were examined by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging and ferrous ion-chelating assays.

RESULTS

The results revealed that subfractions F6-F10, with high proanthocyanidin contents, showed excellent antihyperglycemic and antioxidant activities. Subfractions F6-F10 were analyzed further by matrix-assisted laser desorption/ionization-time of flight/mass spectrometry and thiolysis-reversed-phase high-performance liquid chromatography/tandem mass spectrometry methods. The results showed that the mean degrees of polymerization of proanthocyanidins in subfractions F6-F10 ranged from 3.5 to 5.1, with the highest degrees of polymerization of proanthocyanidins reaching 8 in subfractions F8-F10. Two compounds in F6 were identified as cinnamtannin B1 and parameritannin A1. These proanthocyanidins contained at least one A-type and major B-type linkages.

CONCLUSION

These results demonstrate that proanthocyanidins are associated with their antihyperglycemic and antioxidant activities in CoTE. © 2016 Society of Chemical Industry.

In vitro α-glucosidase inhibitory activity of isolated fractions from water extract of Qingzhuan dark tea

BACKGROUND

Natural products have being used as potential inhibitors against carbohydrate-hydrolyzing enzymes to treat diabetes mellitus. Chinese dark tea has various interesting bioactivities. In this study, the active compounds from Qingzhuan dark tea were separated and their anti-diabetic activity was examined using an in vitro enzymatic model.

METHODS

The chloroform, ethyl acetate, n-butanol, sediment and residual aqua fractions of a Chinese dark tea (Qingzhuan tea) were prepared by successively isolating the water extract with different solvents and their in vitro inhibitory activities against α-glucosidase were assessed. The fraction with the highest inhibitory activity was further characterized to obtain the main active components of Qingzhuan tea.

RESULTS

The ethyl acetate fraction had the greatest inhibitory effect on α-glucosidase, followed by n-butanol, sediment and residual aqua fractions (with the IC₅₀ values of 0.26 mg/mL, 2.94 mg/mL, 3.02 mg/mL, and 5.24 mg/mL, respectively), mainly due to the high content of polyphenols. Among the eight subfractions (QEF1-8) isolated from the ethyl acetate fraction, QEF8 fraction showed the highest α-glucosidase inhibitory potential in a competitive inhibitory manner (the K _i value of 77.10 μg/mL). HPLC-MS analysis revealed that (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) were the predominant active components in QEF8.

CONCLUSION

These results indicated that Qingzhuan tea extracts exerted potent inhibitory effects against α-glucosidase, EGCG and ECG were likely responsible for the inhibitory activity in Qingzhuan tea. Qingzhuan tea may be recommended as an oral antidiabetic diet.

Changes of major tea polyphenols and production of four new B-ring fission metabolites of catechins from post-fermented Jing-Wei Fu brick tea

HPLC analysis of samples from four major fermentation procedures of Jing-Wei Fu brick tea showed that the level of major tea catechins epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) dropped increasingly to about 1/3 in the final product. Phytochemical study of the final product led to the discovery of four new B-ring fission metabolites of catechins (BRFCs) Fuzhuanin C-F (1-4) together with three known BRFCs (5-7), six known catechins (8-13), five simple phenols (14-18), seven flavones and flavone glycosides (19-25), two alkaloids (26, 27), three triterpenoids (28-30) and one steroid (31). The structures were elucidated by spectroscopic methods including 1D and 2D NMR, LC-HR-ESI-MS, IR, and CD spectra. Five compounds (16-18, 28, 29) were reported for the first time in tea. Possible pathways for the degradation of major tea catechins and the generation of BRFCs were also provided.