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The maturity of tea shoots is a key factor influencing its biochemical composition, which in turn affects the quality of processed tea. This study aimed to assess the impact of leaf maturity—specifically, two-leaf and bud (2LB), three-leaf and bud (3LB), and four-leaf and bud (4LB)—on the biochemical constituents in fresh leaves and the quality of CTC black tea. The study was carried out with five commercial cultivars TV9, TV11, TV12, TV23 and S.3 A/3 from Northeast India. As the leaves matured, total polyphenol (TP), total catechin, and caffeine content decreased, while theanine levels increased. Key black tea quality components such as theaflavins, TP, caffeine, thearubigins, and water extract declined significantly (p ≤ 0.05) with increasing leaf maturity, while crude fiber and theanine levels increased. Antioxidant activity in the black tea samples also decreased with leaf maturity, showing a strong positive correlation with TP (R2 = 0.84–0.98) and theaflavins (R2 = 0.79–0.98). Sensory evaluations indicated a preference for 2LB black tea over the others. The chromatic analysis highlighted noticeable differences in the liquor color of black tea made from leaves at the three stages of maturity. These insights can help the tea industry optimize the quality of CTC black tea. [ABSTRACT FROM AUTHOR]

Theaflavin 3,3′‐digallate (TF3), a major polyphenolic component of black tea, exhibits antibacterial effects against many foodborne pathogens. However, the antibacterial mechanisms of TF3 against Listeria monocytogenes remain unclear. In this study, we investigated the effects of TF3 on viability, biofilm, and membrane function of L. monocytogenes by the conventional plating method, crystal violet staining, and microscopy using fluorescent dyes JC‐1 and Laurdan, respectively. It was found that TF3 showed excellent antibacterial activity against L. monocytogenes with the minimum inhibitory concentration of 62.5 mg/L. The viable count determined on TSA decreased by 3 log after the treatment for 2 h with TF3 at 62.5 mg/L. The viable count determined on TSA containing 4% NaCl decreased by more than 4 log after the treatment for 30 min with TF3 at the same concentration, suggesting that TF3 gave damage on the cells, enhancing the antibacterial action of 4% NaCl, but the damage was recoverable in the absence of 4% NaCl. To explore the antibacterial mechanisms of TF3, the effects of TF3 on membrane potential and membrane fluidity were investigated. TF3 reduced both membrane potential and fluidity of L. monocytogenes at 62.5 mg/L, suggesting that TF3 damaged the structural integrity of the cell membrane. TF3 reduced biofilm mass of mature biofilm of L. monocytogenes. Moreover, THEAFLAVIN TF40, a commercially available Camellia sinensis leaf extract containing TF3, reduced viable count of L. monocytogenes by 2 log on apple skin. These results suggest the potential of theaflavins as a natural anti‐Listeria disinfectant. [ABSTRACT FROM AUTHOR]

Aim To investigate the effect of theaflavin on oxidized low density lipoprotein (ox-LDL)-induced foam cell formation and oxidative stress in THP-1 macrophages and its mechanism. Methods THP-1 derived macrophages were pretreated with 50 μmol/L theaflavin and (or) 10 μmol/L nuclear factor erythroid 2-related factor 2 (NRF2) inhibitor ML385, then 100 mg/L ox-LDL was added to the cells for 24 h to establish the foam cell model. The effect of theaflavin on THP-1 macrophages viability was evaluated by CCK-8 assay and LDH release. The expression of inflammatory cytokines interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) were analyzed by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot. The release of inflammatory cytokines were detected by enzyme linked immunosorbent assay (ELISA). Intracellular lipid accumulation was detected by Oil red O staining, and lipid absorption was observed by DiL-labeled oxidized low density lipoprotein (DiL-ox-LDL) staining. Reactive oxygen species (ROS) level was detected by DCFH-DA probe. The expression of lipid uptake, cholesterol efflux and oxidative stress-related proteins were detected by Western blot and RT-qPCR. Results Treatment with 100 mg/L ox-LDL significantly decreased cell viability and cholesterol efflux-related protein expressions, increased lipid uptake, accumulation and lipid uptake-related protein expressions, and significantly promoted inflammation and ROS level, as well as the expressions of myeloperoxidase (MPO), NADPH oxidase 2 (NOX2) in THP-1 macrophages (all P<0. 05). After pretreatment with theaflavin, cell viability was increased, intracellular lipid uptake, accumulation and lipid uptake-related protein expressions were significantly reduced, cholesterol efflux-related protein expressions were significantly increased, the expression and release of IL-6, IL-1β and TNF-α were significantly decreased, ROS level was significantly decreased, and the expression of MPO and NOX2 were decreased (all P<0. 05). Pretreatment with theaflavin effectively alleviated intracellular oxidative stress by altering the expression of NRF2, heme oxygenase-1 (HO-1) and Kelch-like ECH-associated protein 1 (KEAP1) in NRF2 signaling pathway, and enhanced the translocation of NRF2 into the nucleus. After pretreatment with ML385, the expression levels of NRF2, HO-1, KEAP1 and CD36 were significantly decreased. Conclusion Theaflavin can significantly inhibit ox-LDL-induced foam cell formation, inflammation, and oxidative stress through NRF2/HO-1 signaling pathway in THP-1 macrophages. [ABSTRACT FROM AUTHOR]

The ongoing COVID-19 pandemic, caused by SARS-CoV-2, continues to pose significant global health challenges. The results demonstrated that GB-2 at 200 μg/mL effectively increased the population of 293T-ACE2 cells with low RBD binding for both SARS-CoV-2 Omicron EG.5.1 and HV.1 variants by dual-color flow cytometry, indicating its ability to inhibit virus attachment. Further investigation revealed that (+)-catechin at 25 and 50 μg/mL did not significantly alter the ACE2–RBD interaction for the EG.5.1 variant. In contrast, theaflavin showed inhibitory effects at both 25 and 50 μg/mL for EG.5.1, while only the higher concentration was effective for HV.1. Notably, theaflavin 3-gallate exhibited a potent inhibition of ACE2–RBD binding for both variants at both concentrations tested. Molecular docking studies provided insight into the binding mechanisms of theaflavin and theaflavin 3-gallate with the RBD of EG.5.1 and HV.1 variants. Both compounds showed favorable docking scores, with theaflavin 3-gallate demonstrating slightly lower scores (−8 kcal/mol) compared to theaflavin (−7 kcal/mol) for both variants. These results suggest stable interactions between the compounds and key residues in the RBD, potentially explaining their inhibitory effects on virus attachment. In conclusion, GB-2, theaflavin, and theaflavin 3-gallate demonstrate significant potential as inhibitors of the ACE2–RBD interaction in Omicron variants, highlighting their therapeutic promise against COVID-19. However, these findings are primarily based on computational and in vitro studies, necessitating further in vivo research and clinical trials to confirm their efficacy and safety in humans. [ABSTRACT FROM AUTHOR]

Tea polyphenols are considered one of the effective means to reduce protein sensitization, and it is necessary to study their binding mechanism. Therefore, this study investigated the major polyphenol theaflavin (TF) in black tea to investigate its interaction mechanism with egg white lysozyme (LYZ) using multispectral techniques and computer simulations. Molecular global docking and local docking showed that the binding sites of TF and LYZ overlapped highly with the sensitizing linear epitopes. Fluorescence spectroscopy experiments showed that TF formed a ground state complex with LYZ mainly through electrostatic forces to quench its endogenous fluorescence and lead to a decrease in surface hydrophobicity, and the binding reaction proceeded spontaneously; circular dichroism spectra indicated that the addition of TF affected the secondary structure of LYZ. In addition, enzymatic activity assays and in vitro antioxidant assays showed that this interaction slightly reduced the activity of LYZ on the one hand and the antioxidant activity of TF on the other. These results reveal the potential of TF to reduce the allergenicity of egg at the molecular level and provide a theoretical basis for applying tea polyphenols. [ABSTRACT FROM AUTHOR]

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Background: Tea polyphenols have different beneficial effects on vascular endothelium through the controlled production of nitric oxide (NO), regulation of cell proliferation, and antioxidant system. Recently, hydrogen sulfide (H2S) has been proposed as the gaseous signaling molecule in the vascular endothelium. In this study, we investigated the differences in biological functions with tea polyphenols through NO and H2S production in vascular endothelium. Objective: Providing high potential therapeutic effect on vascular endothelium with theaflavin. Results: Theaflavin significantly stimulated H2S production in vascular endothelial cells (VECs) by 1.51-fold compared to the control, while EGCG showed no effect. Both EGCG and theaflavin increased NO production (1.63 and 2.16-fold vs control), eNOS (1.45- and 1.74-fold vs control), p-eNOS (1.41-, 2.01-fold vs control), wound healing (1.30- and 1.75-fold vs control), and oxidative stress-induced reduction of cell viability (89.0 and 94.0% vs control). The potency of theaflavin was found to be higher than that of EGCG. Upon treatment with 100 μM DL-propargylglycine (PPG) to inhibit cystathionine-γ-lyase activity, all cell responses were suppressed in both EGCG and theaflavin treatments, and the reduction rate in the theaflavin treatment was higher than that of the control and EGCG treatments in all responses. Conclusion: These results indicate that the protective effect of VECs is dependent on NO production and that both EGCG and theaflavin have therapeutic potential for VECs. Theaflavin has a relatively higher therapeutic potential than EGCG due to its ability to increase H2S production, which in turn affects NO production and biological activity. [ABSTRACT FROM AUTHOR]

The prevalence and infection of the Zika virus (ZIKV) have recently posed a major threat to global public health security. However, there is currently a lack of specific vaccines and effective antiviral drugs for ZIKV infection. Theaflavins TF1 and TF2 were selected by evaluating the anti-Zika virus activity of four kinds of theaflavins in vitro. Subsequently, in vivo, we investigated the effects of TF1 and TF2 on weight, survival, tissue viral load, and cytokines in ZIKV-infected mice. We compared the anti-ZIKV activity of four theaflavins (TFs) in cells and found that TF1 and TF2b significantly inhibited the replication of ZIKV/Z16006 toxic strain in BHK and Vero cells by inhibiting the replication and release of ZIKV, while no similar effects were observed for TF2a and TF3. In vivo assay, we only found that TF2b improved the survival rate of infected mice. In tissues of ZIKV-infected mice, the viral load was higher in spleen and blood, followed by liver, epididymis, and testis, the lowest in muscle. Additionally, TF2b treatment significantly reduced the expression of cytokines (IL-6 , IL-1β , TNF-α) and chemokines (CCL2 , CCL5 , CXCL10) induced by ZIKV infection. These findings suggest that TF2b has a potent antiviral effect and can be used as a potential candidate for the treatment of ZIKV infection. [ABSTRACT FROM AUTHOR]

Abstract Lumpy skin disease virus (LSDV) infection is a major socio-economic issue that seriously threatens the global cattle-farming industry. Here, a recombinant virus LSDV-ΔTK/EGFP, expressing enhanced green fluorescent protein (EGFP), was constructed with a homologous recombination system and applied to the high-throughput screening of antiviral drugs. LSDV-ΔTK/EGFP replicates in various kidney cell lines, consistent with wild-type LSDV. The cytopathic effect, viral particle morphology, and growth performance of LSDV-ΔTK/EGFP are consistent with those of wild-type LSDV. High-throughput screening allowed to identify several molecules that inhibit LSDV-ΔTK/EGFP replication. The strong inhibitory effect of theaflavin on LSDV was identified when 100 antiviral drugs were screened in vitro. An infection time analysis showed that theaflavin plays a role in the entry of LSDV into cells and in subsequent viral replication stages. The development of this recombinant virus will contribute to the development of LSDV-directed antiviral drugs and the study of viral replication and mechanisms of action.

In this study, a novel preparation method of theaflavin (TF) has been established. Our findings indicated that the formation of TF was significantly enhanced by using an ice bath (2–3°C). Additionally, increasing the ratio of (−)‐epigallocatechin (EGC) under the ice bath could further improve its yield. This approach prevented the appearance of a dark solution within 3 h, effectively protecting TF from oxidation. Our study on the generation mechanism of TF suggested that EGC‐quinone I (EGC‐Q‐I) with two carbanions could potentially serve as one of synthons based on the retrosynthetic analysis of the bicyclo[3.2.1]octane‐type intermediate. Subsequently, quantum mechanical calculations further supported this hypothesis. Practical Application: In this study, we have developed a novel method for the synthesis of theaflavin (TF), demonstrating that the use of ice bath significantly enhanced its yield. Increasing the ratio of (−)‐epigallocatechin (EGC) under the ice bath further improved TF yields and prevented darkening of the solution for at least 3 h, thereby protecting TF from oxidation. Our study suggested that EGC‐quinone I is a potential synthon based on the retrosynthetic analysis of the bicyclo[3.2.1]octane‐type intermediate (BOI). This hypothesis is supported by QM calculations. [ABSTRACT FROM AUTHOR]

Natural dye sensitizers are substances that are sensitive to light colour and can be classified into several classes based on their chemical structure. Theaflavin pigments are unexplored natural dyes used as light sensitizers derived from black tea waste. However, the efficiency of natural dye-sensitized solar cells (DSSC) is lower than that of synthetic ones. To increase the efficiency, an amine donor molecule, a thiophene bridge, and a cyanoacrylic acid anchoring group were added. This improvement was achieved by comparing the LHE values, absorption shifts towards the red spectrum, and electronic parameters before and after modification of the theaflavin structure. This study aimed to analyze the effect of a fused thiophene bridge on the colour pigment of theaflavin on the electronic and optical properties of DSSC. TDDFT was employed with the hybrid functional B3LYP and def2-SVP. The calculated results concluded that adding fused thiophene can shift the wavelength with a maximum value of 256 nm and an increase in LHE of 40%. The addition of five thiophenes can shift the absorption wavelength closer to the red spectrum and satisfy the electronic properties of the DSSC, and the number of electron donor and acceptor sites obeying the law of conservation of charge. [ABSTRACT FROM AUTHOR]

BACKGROUND: Large yellow croaker (Larimichthys crocea) is an economical marine fish consumed in China. Theaflavins have antibacterial and antioxidant properties. However, there is a lack of research into their application in large yellow croakers during refrigerated storage. This study investigated the effect of theaflavins on the quality of large yellow croaker (Larimichthys crocea) during 12 days of storage at 4 °C. RESULTS: The results showed that theaflavin treatment was able to inhibit microbial growth and reduce the production of total volatile basic nitrogen (TVB‐N). Meanwhile, theaflavins were beneficial in reducing the unfolding of myofibrillar proteins, decreasing the degree of protein aggregation, and improving the stability of protein structure. The degree of protein oxidation was lower in a theaflavin‐treated group compared with an untreated group. Theaflavin treatment effectively inhibited increases in acid value (AV), peroxide value (PV), and malonaldehyde (MDA) content. The effect of theaflavin was positively correlated with an increase in concentration under refrigeration conditions. This study therefore suggests that the use of theaflavins is a viable method for extending the period for which refrigerated large yellow croaker can be preserved. CONCLUSIONS: Adding theaflavins to large yellow croaker can be an effective method for preserving quality during refrigerated storage. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Infections caused by Staphylococcus aureus are currently a worldwide threat affecting millions of individuals. The pathogenicity of S. aureus is associated with numerous virulence factors, including cell surface proteins, polysaccharides, and secreted toxins. The pore-forming α-hemolysin, known as α-toxin, is produced by nearly all virulent strains of S. aureus and is implicated in several diseases including skin and soft tissue infections, atopic dermatitis, and pneumonia. There are currently no vaccines available for the prevention of S. aureus infections and the efficacy of available antibiotics has been fading. In this study we examined the mode of antihemolytic activity of theaflavin-3,3'-digallate against α-hemolysin of methicillin-resistant S. aureus by molecular docking using AutoDock Vina as the molecular docking tool. The theaflavin-3,3'-digallate docked the molecular sequence of the Hla (PDB ID:7ahl). The scores of the top 10 binding modes obtained were between 9.0 and 8.5 kcal mol-1, and the best binding mode was 9.0 kcal mol-1 . Direct binding sites of theaflavin-3,30'-digallate to the “stem” domain of Hla were revealed which primarily targeted of the residues Met113, Thr117, Asn139. The disclosure of this potential binding mode warrants further clinical evaluation of theaflavin-3,3'-digallate as an anti-hemolytic compound in order to practically validate our results. [ABSTRACT FROM AUTHOR]

Polyphenol oxidase and its isoenzymes are crucial enzymes in the tea tree that catalyze the synthesis of theaflavins. In this study, tea tree polyphenol oxidase was used as the research object, and various protein sequence treatments, such as TrxA fusion tag + N-terminal truncation, were tested for prokaryotic expression through the Escherichia coli expression system. Comparative analyses were conducted on the activities of the different recombinant enzyme proteins on the substrates of tea polyphenol fractions. Additionally, the enzyme with the highest catalytic efficiency on the TFDG substrate was immobilized using polyethylene glycol to investigate the yield of its synthesis of TFDG. Our results demonstrated that after N-terminal truncation and TrxA fusion expression, CsPPO1, CsPPO2, CsPPO3, and CsPPO4 were mostly expressed in the form of inclusion bodies in the cell and exhibited varying degrees of enhancement in substrate activity. Specifically, CsPPO1 exhibited significantly increased activity in EC and ECG, CsPPO2 showed enhanced activity towards ECG and EGCG, and CsPPO2 displayed the highest activity toward TFDG substrates. Homology modeling structural analysis of the polyphenol oxidase isozymes revealed that the active centers of CsPPO1, CsPPO2, and CsPPO3 consisted of double copper ion center structures, while the conserved histidine residues surrounding the active centers formed different catalytic activity centers in different structures. Furthermore, polyethylene glycol immobilization significantly increased the activity recovery of the CsPPO2 enzyme to 74.41%. In summary, our study elucidated that tea tree polyphenol oxidase is expressed as inclusion bodies in prokaryotic expression, and the activity of the recombinant enzyme towards substrates could be enhanced through N-terminal truncation and TrxA fusion expression. Moreover, immobilization treatment of the CsPPO2 enzyme greatly improved enzyme efficiency. These findings offer an important enzymatic basis and theoretical support for the synthesis of theaflavins. [ABSTRACT FROM AUTHOR]

The mandate of the current investigation was to elucidate the therapeutic and antioxidant perspective of black tea. Purposely, black tea compositional analysis followed by polyphenol extraction and antioxidant characterization was done. Moreover, the theaflavin from black tea extract was also isolated through the solvent partition method. Lastly, the neuroprotective effect of isolated theaflavin was assessed through a bio‐efficacy trial. The outcomes delineated that black tea showed promising nutritional composition with special reference to protein and fiber. Among the extraction solvent, ethanol performed better as compared to methanol and water likewise, higher extraction was noticed at 60 min followed by 90 and 30 min. All the extracts indicated antioxidant activity reflected through significant DPPH, TPC, FRAP, and beta carotene as‐69.13 ± 3.00, 1148.92 ± 14.01, 752.44 ± 10.30, and 65.74 ± 3.28, respectively. However, isolated theaflavin exhibited higher antioxidant capacity as‐737.74 ± 12.55, 82.60 ± 2.33, and 853.77 ± 9.55, for TPC, DPPH, and FRAP, respectively, as compared to extracts. In 15 days' efficacy was physically induced with sciatic nerve injury h sciatic nerve injury physically and treated with isolated theaflavin. A total of 12 healthy albino mice were randomly assigned to either the control (n = 6) or theaflavin (5.0 mg/kg (n = 6)) groups. In these groups, behavioral tests were used to assess and compare enhanced functional recovery as well as skeletal muscle mass measurement. Serum samples included oxidative stress markers. In theaflavin leaves, behavioral tests revealed a statistically significant (p <.001) improvement in sensorimotor function restoration, muscle mass restoration, a substantial decrease in TOS, a significant increase in TAC, and enhanced antioxidative enzyme activity. Considering the above‐mentioned therapeutic perspectives of theaflavin, the current research was planned to optimize the isolation of theaflavin from black tea and probed for their neuroprotective effect in mice models. [ABSTRACT FROM AUTHOR]

African swine fever virus (ASFV) is the etiological agent of African swine fever (ASF), which is one of the most harmful swine diseases in the pig industry because of its nearly 100% mortality rate in domestic pigs and results in incalculable economic loss. Ever since ASF was initially reported, scientists have worked to develop anti-ASF vaccines; however, currently no clinically effective vaccine for ASF is available. Therefore, the development of novel measures to prevent ASFV infection and transmission is essential. In this study, we aimed to investigate the anti-ASF activity of theaflavin (TF), a natural compound mainly isolated from black tea. We found that TF potently inhibited ASFV replication at non-cytotoxic concentrations ex vivo in primary porcine alveolar macrophages (PAMs). Mechanistically, we found that TF inhibited ASFV replication by acting on cells rather than interacting directly with ASFV to inhibit viral replication. Further, we found that TF upregulated the AMPK (5′-AMP-activated protein kinase) signaling pathway in ASFV-infected and uninfected cells, and treatment with the AMPK agonist MK8722 upregulated the AMPK signaling pathway and inhibited ASFV proliferation in a dose-dependent manner. Notably, the effects of TF on AMPK activation and ASFV inhibition were partially reversed by the AMPK inhibitor dorsomorphin. In addition, we found that TF down-regulated the expression of genes related to lipid synthesis and decreased the intracellular accumulation of total cholesterol and total triglycerides in ASFV-infected cells, suggesting that TF may inhibit ASFV replication by disrupting lipid metabolism. In summary, our results demonstrated that TF is an ASFV infection inhibitor and revealed the mechanism by which ASFV replication is inhibited, providing a novel mechanism and potential lead compound for the development of anti-ASFV drugs.

Streptococcus suis (S. suis) is one of the most important zoonotic pathogens that threaten the lives of pigs and humans. Even worse, the increasingly severe antimicrobial resistance in S. suis is becoming a global issue. Therefore, there is an urgent need to discover novel antibacterial alternatives for the treatment of S. suis infection. In this study, we investigated theaflavin (TF1), a benzoaphenone compound extracted from black tea, as a potential phytochemical compound against S. suis. TF1 at MIC showed significant inhibitory effects on S. suis growth, hemolytic activity, and biofilm formation, and caused damage to S. suis cells in vitro. TF1 had no cytotoxicity and decreased adherent activity of S. suis to the epithelial cell Nptr. Furthermore, TF1 not only improved the survival rate of S. suis-infected mice but also reduced the bacterial load and the production of IL-6 and TNF-α. A hemolysis test revealed the direct interaction between TF1 and Sly, while molecular docking showed TF1 had a good binding activity with the Glu198, Lys190, Asp111, and Ser374 of Sly. Moreover, virulence-related genes were downregulated in the TF1-treated group. Collectively, our findings suggested that TF1 can be used as a potential inhibitor for treating S. suis infection in view of its antibacterial and antihemolytic activity. [ABSTRACT FROM AUTHOR]

The interaction mechanism of whey proteins with theaflavin (TF1) in black tea was analyzed using multi-spectroscopy analysis and molecular docking simulations. The influence of TF1 on the structure of bovine serum albumin (BSA), β-lactoglobulin (β-Lg), and α-lactoalbumin (α-La) was examined in this work using the interaction of TF1 with these proteins. Fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy revealed that TF1 could interact with BSA, β-Lg and α-La through a static quenching mechanism. Furthermore, circular dichroism (CD) experiments revealed that TF1 altered the secondary structure of BSA, β-Lg and α-La. Molecular docking demonstrated that the interaction of TF1 with BSA/β-Lg/α-La was dominated by hydrogen bonding and hydrophobic interaction. The binding energies were −10.1 kcal mol−1, −8.4 kcal mol−1 and −10.4 kcal mol−1, respectively. The results provide a theoretical basis for investigating the mechanism of interaction between tea pigments and protein. Moreover, the findings offered technical support for the future development of functional foods that combine tea active ingredients with milk protein. Future research will focus on the effects of food processing methods and different food systems on the interaction between TF1 and whey protein, as well as the physicochemical stability, functional characteristics, and bioavailability of the complexes in vitro or in vivo. [ABSTRACT FROM AUTHOR]

To explore the inhibitory effect and mechanism of theaflavin (TF1), human hepatoma carcinoma Bel-7402 cells were treated with different concentrations of TF1. Cell viability was detected by CCK8 and cell proliferation was detected by colony formation assay. Cell migration was detected by cell wound healing experiment and transwell chamber assay. Cell apoptosis was detected by flow cytometry. Apoptosis-related proteins (Bax, Bcl-2, PARP), migration related proteins (E-cad, N-cad, Vimentin, MMP9) and signaling pathway related proteins (TGF-β, Smad3, p-smad3) were detected by western blot. The results show that different concentrations of TF1 could inhibit the proliferation and migration of Bel-7402 cells and promote their apoptosis in a dose-dependent manner. The higher the dose, the stronger the inhibition effect (P<0.05). Compared with the control group, the expression levels of Bax and E-cad proteins in the experimental group were higher, while the expression levels of Bcl-2, PARP, N-cad, Vimentin, MMP9, TGF-β, Smad3 and p-smad3 were lower (P<0.05). In conclusion, TF1 could inhibit the proliferation and migration of Bel-7402 cells and promote their apoptosis through TGF-β signaling pathway. [ABSTRACT FROM AUTHOR]

ABSTRACT: Increasing evidence has shown that gut microbiota plays important roles in metabolizing large molecular polyphenols to bioavailable and bioactive microbial metabolites. Theaflavin (TF) is one of the major color compounds in black tea and has demonstrated anti-inflammation, antioxidant, and anticancer effects properties. However, little is known about the metabolism of TF by gut microbiota in vivo. In this study, following the administration of TF to mice, the C-ring cleavage metabolites, dihydro- and tetrahydro-theaflavin (DH-TF and TH-TF) were detected in mouse feces by LC-MS and validated by authentic standards from in situ chemical reaction. The observation of the C-ring cleavage metabolites in TF-treated conventionalized mice but not in germ-free (GF) mice confirmed the role of gut microbiota in cleaving the C-rings of TF. The detection of DH-TF from the anaerobic incubation of TF with catechin-converting gut bacteria, Eggerthella lenta (Eggerth), suggested that the microbes with the capacity to cleave the C-ring of catechins were able to metabolize TF following the same mechanism. Additionally, three small phenolic metabolites were detected in mouse feces, and one of them was primarily detected in SPF mice not GF mice, which revealed that TF, subsequent to the cleaved C-ring, can be further metabolized into smaller phenolic metabolites by gut microbiota. Dose-dependent production of these metabolites were observed from the administration of 100 mg/kg to 400 mg/kg body weight of TF. In conclusion, gut microbiota can metabolize TF to the open-ring metabolites and the phenolic metabolites through the C-ring cleavage in mice.

In this study, non-covalent binding mechanism of lactoferrin (LaF)-theaflavin (TF) complex and its functional properties were investigated. Multi-spectroscopic analyses showed that the secondary structure of LaF was altered with increasing TF concentration. The non-covalent binding of TF to LaF resulted in a reduction in the content of the α -helix and β -sheet, as well as a decrease in the fluorescence intensity of LaF. DSC result showed that non-covalent binding of TF improved thermal stability of LaF. Molecular dynamics simulations confirmed that the stable binding of LaF-TF was driven by hydrogen bonding and hydrophobic interactions. Additionally, non-covalent binding of TF increased the antioxidant capacity and emulsifying properties of LaF. Dynamic interfacial tension indicated that the strong interaction between LaF and TF reduced the interfacial tension, but improved the rheological properties of LaF. The functional characteristics of the non-covalent complex was effectively enhanced, paving the way for its potential use in the food industry. [Display omitted] • Interaction mechanism between lactoferrin (LaF) and theaflavin (TF) was elucidated. • Non-covalent binding of TF altered the secondary structure and functional properties of LaF. • Binding between LaF and TF was driven by hydrogen bonding and hydrophobic interaction. • Addition of TF improved the thermal stability, antioxidant capacity and emulsifying properties of LaF. • Non-covalent binding of TF to LaF reduces their interfacial tension and viscosity. [ABSTRACT FROM AUTHOR]

The corona virus disease 2019 (COVID-19) pandemic, which originated in the city of Wuhan, China, has rapidly spread to various countries, with many cases having been reported. Some existing antiviral agents showed positive results to inhibit the infection and transmission of the novel corona virus 2019 (2019-nCoV) in vitro. Covaxin is India's first indigenous COVID-19 vaccine. In this paper, we introduce the Gourava and hyper-Gourava polynomials of a graph. We compute the Gourava and hyper-Gourava polynomials of some specific class of graphs. Further, we obtain the Gourava and hyper-Gourava polynomials of some chemical structures viz., chloroquine, hydroxychloroquine, remdesivir and theaflavin which were used in the treatment of COVID-19. The Gourava and hyper-Gourava indices are investigated for the aforesaid antiviral drugs using polynomial approach. The Indian Council of Medical Research and Bharat Biotech announced that Phase 3 results of covaxin, developed by them, have shown an interim vaccine efficacy of 81 percent. So, the results obtained may be useful for finding the design of new medicine for the treatment of COVID-19. [ABSTRACT FROM AUTHOR]

Objective To investigate the protective effects of dietary intervention with theaflavin-3, 3'-digallate (TFDG) on liver injury induced by high-fat diet (HFD) in mice and its underlying mechanism. Methods Forty C57BL/6 mice were randomly and equally divided into normal control (NC), model control (MC) and TFDG administration (TF5 and TF10) groups. The mice of the NC group were fed with normal diet, and those of the other 3 groups were given HFD. Then the TF5 and TF10 groups were intragastrically given 5 mg/kg and 10 mg/kg TFDG respectively, while the NC and MC groups were treated with normal saline. After 12 weeks of intervention, the liver index, serum ALT and AST levels were detected, and the pathological changes of liver tissues were observed in the mice. The contents of inflammatory factors and the expression levels of related proteins in liver tissue were determined by ELISA and Western blotting respectively, and the mRNA level of miR-233 was measured by qRT-PCR. Results HFD significantly increased the liver index as well as serum ALT and AST levels, while these changes were effectively reversed by TFDG administration (P < 0.05). Pathological observation displayed that TFDG intervention reduced the formation of lipid droplets in liver tissue, and lipid content detection also suggested that TFDG remarkably declined the levels of triglyceride (TG) and total cholesterol (TC) in liver tissue (P < 0.05). ELISA indicated that the levels of IL-1β, IL-6 and TNF-α were elevated notably in the liver of HFD-fed mice, and Western blotting confirmed higher protein levels of NLRP3, caspase-1 and IL-1β, whereas TFDG inhibited the inflammatory response of liver (P < 0.05) and the activation of NLRP3/IL-1β pathway (P < 0.05). In addition, TFDG intervention greatly up-regulated the expression of miR-223 in the hepatocytes under high-fat condition. After oligonucleotide inhibitor blocked the effect of TFDG on miR-223 expression, its inhibitory effect on inflammatory response was weakened as well (P < 0.05). Conclusion TFDG can effectively alleviate liver injury and inflammatory response induced by HFD, which may be through up-regulation of miR-223 to inhibiting NLRP3 pathway.

Objective(s): This study aimed to investigate the mechanism of the anticancer effect of theaflavin (TF) in nasopharyngeal carcinoma.Materials and Methods: CNE2 cells were used to study the anticancer effect of TF. This study used Cell Counting Kit-8 (CCK8) assay on proliferation and used flow cytometry to detect apoptosis. The protein expression of Bcl-2, Bax, caspase 3, and caspase 9 was detected by Western blot, and autophagy-related proteins were also detected.Results: TF inhibited proliferation of CNE2 cells, promoted apoptosis, and up-regulated the expression of caspase 3, caspase 9, and Bax, and decreased the level of Bcl-2. Unexpectedly, TF induced autophagy rather than inhibiting autophagy through up-regulating the levels of the autophagy marker light chain 3 (LC3) and Lysosomal-associated membrane protein 1 (LAMP1) and reducing levels of the autophagosome cargo protein p62, and the effect was via the mTOR pathway. Besides, autophagy inhibitor Chloroquine (CQ) suppressed the effect of TF on Bax, Bcl-2 and activation of caspase 3 and caspase 9.Conclusion: TF promoted apoptosis of nasopharyngeal carcinoma cells, the mechanism was unexpectedly involved in inducing autophagy.

Recurrent epidemics of methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA) have illustrated that the effectiveness of antibiotics in clinical application is rapidly fading. A feasible approach is to combine natural products with existing antibiotics to achieve an antibacterial effect. In this molecular docking study, we found that theaflavin (TF) preferentially binds the allosteric site of penicillin-binding protein 2a (PBP2a), inducing the PBP2a active site to open, which is convenient for β-lactam antibiotics to treat MRSA infection, instead of directly exerting antibacterial activity at the active site. Subsequent TMT-labeled proteomics analysis showed that TF treatment did not significantly change the landscape of the S. aureus USA300 proteome. Checkerboard dilution tests and kill curve assays were performed to validate the synergistic effect of TF and ceftiofur, and the fractional inhibitory concentration index (FICI) was 0.1875. The antibacterial effect of TF combined with ceftiofur was better than that of single-drug treatment in vitro. In addition, TF effectively enhanced the activity of ceftiofur in a mouse model of MRSA-induced pneumonia. Our findings provide a potential therapeutic strategy to combine existing antibiotics with natural products to resolve the prevalent infections of multidrug-resistant pathogens.

Polyphenol oxidase and its isoenzymes are crucial enzymes in the tea tree that catalyze the synthesis of theaflavins. In this study, tea tree polyphenol oxidase was used as the research object, and various protein sequence treatments, such as TrxA fusion tag + N-terminal truncation, were tested for prokaryotic expression through the Escherichia coli expression system. Comparative analyses were conducted on the activities of the different recombinant enzyme proteins on the substrates of tea polyphenol fractions. Additionally, the enzyme with the highest catalytic efficiency on the TFDG substrate was immobilized using polyethylene glycol to investigate the yield of its synthesis of TFDG. Our results demonstrated that after N-terminal truncation and TrxA fusion expression, CsPPO1, CsPPO2, CsPPO3, and CsPPO4 were mostly expressed in the form of inclusion bodies in the cell and exhibited varying degrees of enhancement in substrate activity. Specifically, CsPPO1 exhibited significantly increased activity in EC and ECG, CsPPO2 showed enhanced activity towards ECG and EGCG, and CsPPO2 displayed the highest activity toward TFDG substrates. Homology modeling structural analysis of the polyphenol oxidase isozymes revealed that the active centers of CsPPO1, CsPPO2, and CsPPO3 consisted of double copper ion center structures, while the conserved histidine residues surrounding the active centers formed different catalytic activity centers in different structures. Furthermore, polyethylene glycol immobilization significantly increased the activity recovery of the CsPPO2 enzyme to 74.41%. In summary, our study elucidated that tea tree polyphenol oxidase is expressed as inclusion bodies in prokaryotic expression, and the activity of the recombinant enzyme towards substrates could be enhanced through N-terminal truncation and TrxA fusion expression. Moreover, immobilization treatment of the CsPPO2 enzyme greatly improved enzyme efficiency. These findings offer an important enzymatic basis and theoretical support for the synthesis of theaflavins.

Pickled tea is an ethnic fermented product produced using Assam tea (Camellia sinensis var. assamica) leaves. It is produced in large quantities every year and the liquid waste from its production is estimated to be up to 2500 mL per every kilogram of pickled tea production. To reduce the waste, pickled tea juice remaining from the process was developed into (1) pineapple kombucha and (2) formulated functional drinks as "value added" products. The juice used for making kombucha was collected at 15 days of pickled tea fermentation due to its high value in antioxidant activity (previous study, 2250 µmol TE per g DW). After fermenting the juice with starter culture, the properties of pineapple kombucha were assessed at 0, 1, 3, 5, 7, 9, 11 days. Results showed that the total phenolic of pineapple kombucha was reduced, while antioxidant assay (FRAP and ORAC) slightly increased. The most suitable fermentation period of pineapple kombucha was at day 3. The formulated drink was made from mixing pineapple kombucha with ginger and lemon juice at various ratios including 100:0:0, 80:10:10 and 80:15:5. The ratio 80:10:10 gave the highest TP and antioxidant activity for the functional drink. In addition, for sensory analysis, liking attribute of 80:15:5 fermented juice kombucha pineapple favor was significantly higher compared to other formulations. The study demonstrates the promising second fermentation process of by-product juice from pickled tea production for the conversion to value-added functional drink with reasonable antioxidant properties. [ABSTRACT FROM AUTHOR]

Summary: Polyphenol oxidase (PPO) plays an important role in tea production, and there are many studies on the enzymatic synthesis of theaflavins using PPO; however, using a purified PPO isozyme (PPOI) instead of a crude PPO enzyme to obtain monomeric theaflavin in vitro is a novel approach that has rarely been previously reported. In the present study, a tea PPOI was purified and used for the enzymatic synthesis of theaflavin monomers. Tea leaf PPOI was purified 12.90‐fold, with recovery yield of 1.30% via the sequential use of precipitation with 30%−80% saturated (NH4)2SO4, Q‐Sepharose Fast Flow anion exchange chromatography and Sephadex G‐75 gel filtration chromatography. Subsequently, PPOI was used in the enzymatic synthesis of theaflavins: under various pH, temperatures, reaction times and catechin substrate composition and concentration, only the amount of theaflavin components produced was changed, and no other theaflavin component apart from the theaflavin monomer was produced. These results highlight the importance of monomeric theaflavin synthesis using purified PPOI isozyme and provide insight into PPO in the context of tea production. [ABSTRACT FROM AUTHOR]

BACKGROUND: Theafiavin-3-gallate (TF-3G) can significantly inhibit bone resorption and has obvious effects on preventing osteoporosis, but its application on osteogenesis is rare OBJECTIVE: TF-3G was loaded into nano-hydroxyapatite/polycaprolactone composite scaffold to observe its osteogenic effect. METHODS: TF-3G solution of different mass concentrations was prepared. The cytotoxicity of TF-3G was detected by CCK-8 assay. According to cytotoxicity test results, bone marrow mesenchymal stem cells were intervened by TF-3G solution of appropriate mass concentration (0, 0.86, 4.30, 8.60, 17.20, 34.4, 68.8, 86, 106 mg/L). CCK-8 assay was used to detect its proliferative activity during osteogenic differentiation. A certain concentration of TF-3G solution was selected to induce bone marrow mesenchymal stem cells to differentiate towards osteogenic direction, and alkaline phosphatase activity detection and alizarin red staining were performed. Nano-hydroxyapatite/polycaprolactone composite porous scaffold was prepared using selective laser sintering rapid prototyping technology. TF-3G was loaded into nano-hydroxyapatite/polycaprolactone composite porous scaffold by solution impregnation and freeze-drying. A 1.5 cm bone defect was made in the radius of adult New Zealand white rabbits. The blank control group was not implanted with any material. The two experimental groups were implanted with nano-hydroxyapatite/polycaprolactone, and TF-3G/nano-hydroxyapatite/polycaprolactone composite porous scaffold. The imaging examination and histological observation were performed after operation. RESULTS AND CONCLUSION: (1) CCK-8 assay showed that 0.86, 4.30, 8.60 mg/L TF-3G promoted the proliferation of bone marrow mesenchymal stem cells; 17.20, 34.4, 68.8, 86, 106 mg/L TF-3G inhibited the proliferation of bone marrow mesenchymal stem cells; 0.86, 4.30, 8.60 mg/L mass concentration was chosen for osteoinduction experiment. (2) Alkaline phosphatase activity detection and alizarin red staining showed that with the increased mass concentration of TF-3G solution, the bone formation effect was enhanced. (3) Lane-Sandhu X-ray scores at 4 and 12 weeks after operation in the two experimental groups were higher than those in the blank control group (P < 0.05), and the scores were higher in the TF-3G/nano-hydroxyapatite/polycaprolactone group than those in the nano-hydroxyapatite/polycaprolactone group (P < 0.05). (4) At 12 weeks after operation, combined with the results of hematoxylin-eosin staining and Masson staining, Huddleston histological score of the two experimental groups was higher than that of the blank control group (P < 0.05), and the score in the TF-3G/nano-hydroxyapatite/polycaprolactone group was higher than that of the nano-hydroxyapatite/polycaprolactone group (P < 0.05). (5) Results concluded that TF-3G can promote the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. Nano-hydroxyapatite/polycaprolactone composite porous scaffold loaded with TF-3G can promote the repair of bone defects. [ABSTRACT FROM AUTHOR]

In this study, pH-responsive whey protein (WP)/sodium alginate (SA) composite hydrogel beads using the ionic gelation method were described and evaluated for their potential as delivery carriers for theaflavin (TF). Fourier transform infrared spectroscopy (FTIR) confirmed the interaction between WP and SA in the hydrogel beads is driven primarily by the strong intermolecular interactions, including hydrogen bonding and electrostatic attractions. The swelling ratio of the beads possesses good pH dependence and pH reversibility, effectively preventing the release of TF in the gastric environment. The encapsulation efficiency (EE) of TF in hydrogel beads ranged from 94.995 ± 0.03 to 95.709 ± 0.14, with a loading capacity (LC) of 27–34 mg/g. In in vitro digestion simulations, owing to the pH responsiveness, hydrogel beads released minimal TF throughout gastric digestion and were fully released in the intestine phase. Additionally, the release kinetics of TF from the beads were further examined in a simulated intestinal environment. These findings suggest that the hydrogel bead system is a promising carrier for encapsulating TF, offering a theoretical and experimental basis for its future application in the food industry. • Whey protein/sodium alginate hydrogel beads were used for theaflavin encapsulation. • WP/SA composite hydrogel beads exhibited pH sensitivity and pH reversibility. • The intermolecular interaction between WP and SA was mainly on hydrogen bonding. • WP/SA/TF hydrogel beads exhibited high encapsulation efficiency. • This system effectively protects TF in gastric and release in intestinal digestion. [ABSTRACT FROM AUTHOR]

The antimicrobial and antileukemic effect of a purified fraction of flavonoids from the leaves of Camellia sinensis was evaluated. An extraction yield of 9.77 mg.g-1 total flavonoids was recovered through a pressurized liquid extraction associated with solid-phase extraction. This fraction was tested against pathogenic microorganisms (Staphylococcus, Salmonella, and Enterococcus), considering the minimum inhibitory concentration. In addition, the human monocyte cell line THP-1, derived from a patient with acute monocytic leukemia, was used for the antitumor assay. The results show that the flavonoid-rich fraction obtained by coupling a Pressurized Liquids Extraction in-line with a Solid Phase Extraction (PLE-SPE) has a high antimicrobial effect and resulted in cell cycle blockage G0 / G1, increased DNA fragmentation, and altered leukemic cell morphology. These results suggest that a flavonoid-rich fraction obtained from Camellia sinensis can be applied as potential adjuvants in chemotherapy treatment to mitigate the side effects caused by chemotherapy or even as a supplement to cancer therapy.

Abstract Background COVID-19 has mutation capability, and there are no specific drug therapies that are available to fight or inhibit the proteins of this virus. The present study aims to investigate the binding affinity of the bioactive and synthetic compounds with the main protease (Mpro) enzymes and angiotensin-converting enzyme 2 (ACE 2) by computational approach. PASS prediction, pharmacokinetics, and toxicological properties prediction studies were performed through the Google PASS prediction and Swiss ADME/T website. Besides, molecular docking studies were accomplished by BIOVIA Discovery Studio 2020, UCSF Chimera, and PyRx autodock vina. Results The docking scores were inferred and the selected compounds showed results varying from −3.2 to −9.8 (kcal/mol). Theaflavin scored the highest docking score to the 5REB, 6VW1, and 1R42 enzymes and showed the binding affinity as −6.3 kcal/mol, −9.8 kcal/mol, and −8.6 kcal/mol, respectively. Again, kaempferol showed the best binding affinity to the 7BQY (−7.1 kcal/mol) and 6Y2FB (−6.6 kcal/mol) enzymes. All the chemical constituents showed better probability in action in pass prediction analysis. Besides, no ligands (except theaflavin) have any conflict with Lipinski’s rules of five, which authorized the drug probability of these ligands. Conclusion Therefore, the selected compounds could be considered a potential herbal treatment source against SARS-CoV-2.

At present, consumers increasingly favored the natural food preservatives with fewer side-effects on health. The green tea catechins and black tea theaflavins attracted considerable interest, and their antibacterial effects were extensively reported in the literature. Epicatechin (EC), a green tea catechin without a gallate moiety, showed no bactericidal activity, whereas the theaflavin (TF), also lacking a gallate moiety, exhibited potent bactericidal activity, and the antibacterial effects of green tea catechins and black tea theaflavins were closely correlated with their abilities to disrupt the bacterial cell membrane. In our present study, the mechanisms of membrane interaction modes and behaviors of TF and EC were explored by molecular dynamics simulations. It was demonstrated that TF exhibited markedly stronger affinity for the POPG bilayer compared to EC. Additionally, the hydrophobic interactions of tropolone/catechol rings with the acyl chain part could significantly contribute to the penetration of TF into the POPG bilayer. It was also found that the resorcinol/pyran rings were the key functional groups in TF for forming hydrogen bonds with the POPG bilayer. We believed that the findings from our current study could offer useful insights to better understand the stronger antibacterial effects of TF compared to EC. [Display omitted] • We explored the mechanisms of interactions between TF/EC and bilayers by MD. • Theaflavin showed a markedly stronger affinity for the POPG bilayer compared to EC. • Hydrophobic and h-bond interactions enabled TF's insertion into POPG bilayer. • Resorcinol/pyran rings were key functional groups to form h-bonds with POPG bilayer. [ABSTRACT FROM AUTHOR]

[Display omitted] • SDS-PAGE showed that TF modification increased the molecular weight of LYZ. • Multispectral experiments showed that TF modification changed the secondary structure. • TF modification increased the antioxidant capacity and thermal stability of LYZ. • TF modification decreased the enzymatic activity and antimicrobial properties of LYZ. Proteins modified by polyphenols have more advantages. In this study, we investigated the effect of covalent conjugation of egg white lysozyme (LYZ) with theaflavin (TF) on its structure and related functions. The LYZ-TF covalent conjugation was prepared by an alkaline method (pH 9.0) with a branching rate of about 80%. The results such as SDS-PAGE and UV spectroscopy proved the formation of the covalent conjugation. The results of fluorescence and infrared spectroscopy showed that the conformation of the LYZ-TF coupling was altered, with an increase in α-helix content by more than 10% and an increase in surface hydrophobicity compared to LYZ. The results of relevant functional characterization experiments showed the thermal stability and antioxidant properties of LYZ modified by TF, but its enzymatic activity and in vitro antimicrobial properties were inhibited. Notably, the amount of TF addition also affected the structure and function of the conjugates. These results provide some theoretical guidance for the development of novel food functional materials with enhanced properties. [ABSTRACT FROM AUTHOR]

Tyrosinase is a key metalloenzyme for the biosynthesis of melanin that plays a critical role in the prevention of skin damage caused by ultraviolet (UV) radiation. However, the overproduction of melanin may cause a variety of skin diseases. Due to the toxicity and inefficiency of existing tyrosinase inhibitors, it is urgent to identify safe and potent alternatives from natural sources. Theaflavin, a single‐component extracted from black tea, has been found to possess a variety of pharmacological activities. Herein, the inhibition kinetics of theaflavin on tyrosinase and inhibitory mechanism were determined using spectroscopy, molecular docking, and zebrafish model. The results showed that theaflavin inhibited the diphenolase activity of tyrosinase in a reversible mixed type manner with IC50 of 229.75 μmol/L and hindered the synthesis of melanin in zebrafish. This may be due to the formation of eight hydrogen bonds and hydrophobic effects between theaflavin and tyrosinase according to the results of molecular docking. To study the possible effects on the prevention of free radical‐mediated skin cancer and photoaging caused by UV radiation, the antioxidation and UV filter properties of theaflavin were further verified. This study demonstrates that theaflavin is a potential multifunctional compound that can be used in cosmetic and medicinal products. [ABSTRACT FROM AUTHOR]

BACKGROUND The phenol oxidative pathway during fermentation remains unclear. To elucidate the effect of fermentation on phenol conversion, we investigated the effects of fermentation temperature and duration on the conversion of catechins and the formation of theasinensins (TSs), theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). RESULTS: During fermentation, TSs formation increased initially and then decreased. Long fermentation durations were unfavorable for liquor brightness (LB) and resulted in the production of large amounts of TRs and TBs. Low fermentation temperatures (20 °C and 25 °C) favored the maintenance of polyphenol oxidase activity and the continuous formation of TFs, TSs, and TRSI (a TRs fraction), resulting in better LB and liquor color. Higher temperatures (30 °C, 35 °C, and 40 °C) resulted in higher peroxidase activity, higher oxidative depletion rates of catechins, and excessive production of TRSII (a TRs fraction) and TBs. Analysis of the conversion pathway of polyphenolic compounds during fermentation showed that, during early fermentation, large amounts of catechins were oxidized and converted to TFs and theasinensin B. As fermentation progressed, considerable amounts of theaflavin‐3′‐gallate, theasinensin A, theaflavin‐3‐gallate, theaflavin‐3,3′‐digallate, and theasinensin C were produced and then converted to TRSI; in the final stage, TRSII and TBs were converted continuously. CONCLUSION: Different fermentation temperature and duration combinations directly affected the type and composition of phenolic compounds. The key conditions for controlling phenolic compound conversion and fermentation direction were 60 or 90 min and 25 or 30 °C. Our study provides insights into the regulation of phenolic compound conversion during black tea fermentation. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The novel coronavirus disease 2019 (COVID-19) emerged in Wuhan, China, and has spread rapidly to nearly every part of the world. Unfortunately, no drug or vaccine has been accepted for the treatment of this pandemic. Researchers have established the efficacy of some existing antiviral drugs to control COVID-19 in vitro. Some of them are remdesivir (GS-5734), chloroquine, hydroxychloroquine, theaflavin. Topological indices are mathematical interpretations of a molecule generated by an algorithm implemented to a given molecular representation. Topological indices are used to model different physicochemical properties and biological activities of chemical compounds. In this work, some degree-based and neighborhood degree sum-based topological indices are investigated for the aforesaid antiviral drugs using polynomial approach. The results obtained can aid in the design of new medicine for the treatment of COVID-19. [ABSTRACT FROM AUTHOR]

K+ availability is important for growth and quality of tea (Camellia sinesis L.). K solubilising bacteria convert insoluble K to available K. This study was conducted to screen K solubilising bacteria isolated from tea rhizosphere soil in Qimen county, Anhui province, China. The maximum K solubilisation colony (the ratio of diameter halo/colony was 2.54) was identified as Burkholderia sp. (storage number: M2021105) by biochemistry and molecular analysis. Pot experiments (Laterite) showed that the inoculation of Burkholderia sp. significantly improved tea plant height (Zhongcha108, 1 year old) and total polyphenols content by 21.14% and 21.58% compared with the control, respectively. Higher polyphenol level promoted the formation of theaflavin in the fermentation experiments. Further experiments showed that tartaric acid and pryuvic acid produced by Burkholderia sp. are important components associated with K solubilisation in vitro. Burkholderia sp. significantly increased soil available K by 15.12%; however, there was no significant difference in available N and P, and Cu, Mg, Zn and Ca compared with the control. K content in inoculated tea roots and leaves was significantly higher (50% and 10%, respectively) than the control. Compared with the control, exogenous supply of 60 mg kg-1 K significantly increased levels of polyphenol (53.97%), theaflavin (16.31%), theaflavin-3-gallate (20%), theaflavin 30-gallic acid ester (32.24%) and theaflavin 3,3 0-gallic acid ester (40.95%). Due to its ability to enable higher available soil K, ur study indicated that Burkholderia sp. have potential to increase total polyphenols content be a bio-inoculant for biofortification of tea. [ABSTRACT FROM AUTHOR]

The treatment of wounds remains a clinical challenge because of poor angiogenesis under the wound bed, and increasingly, the patients’ need for functional and aesthetically pleasing scars. Previous reports have shown that Theaflavin can induce angiogenesis and terminate the progression of ischemic cardiovascular disease, but limited therapy is available for the management of cutaneous wounds. In this study, our in vitro work discovered that human umbilical vein endothelial cells (HUVECs) exposed to Theaflavin can alleviate apoptosis and cell dysfunction induced by tert-butyl hydroperoxide (TBHP). The cellular activity of HUVECs were assessed by cell tube formation, migration and adhesion. Mechanistically, Theaflavin protected HUVECs from TBHP-stimulated cell apoptosis through the activation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor (erythroid-derived 2)-like 2 (Nrf2) axis, so Nrf2 silencing can partly eliminate the cytoprotective effect of Theaflavin treatment. In in vivo experiments, administering Theaflavin orally can enhance vascularization in regenerated tissues and accelerate wound healing. In summary, our data served as a novel evidence for the wound healing treatment with Theaflavin, and certified the potential mechanism of Theaflavin, which can be used as a potential agent for cutaneous wound therapy.

The interaction mechanism of whey proteins with theaflavin (TF1) in black tea was analyzed using multi-spectroscopy analysis and molecular docking simulations. The influence of TF1 on the structure of bovine serum albumin (BSA), β-lactoglobulin (β-Lg), and α-lactoalbumin (α-La) was examined in this work using the interaction of TF1 with these proteins. Fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy revealed that TF1 could interact with BSA, β-Lg and α-La through a static quenching mechanism. Furthermore, circular dichroism (CD) experiments revealed that TF1 altered the secondary structure of BSA, β-Lg and α-La. Molecular docking demonstrated that the interaction of TF1 with BSA/β-Lg/α-La was dominated by hydrogen bonding and hydrophobic interaction. The binding energies were −10.1 kcal mol−1, −8.4 kcal mol−1 and −10.4 kcal mol−1, respectively. The results provide a theoretical basis for investigating the mechanism of interaction between tea pigments and protein. Moreover, the findings offered technical support for the future development of functional foods that combine tea active ingredients with milk protein. Future research will focus on the effects of food processing methods and different food systems on the interaction between TF1 and whey protein, as well as the physicochemical stability, functional characteristics, and bioavailability of the complexes in vitro or in vivo.

Tea, and particularly bottled tea, is widely consumed worldwide and is often encountered at crime scenes in poisoning cases or used in place of urine in drug abuse monitoring. Tea is a rich source of polyphenols, such as catechins and theaflavins, and these compounds are useful for identification of trace quantities of tea samples. However, information on the contents of catechins and theaflavins in bottled tea is limited. In this study, a method was developed for simultaneous analysis of eight catechins and four theaflavins in tea using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). The concentrations of these polyphenols were determined in bottled black, oolong, and green teas after a simple pretreatment process by the standard addition method. The developed LC‐MS/MS method was rapid and all tested polyphenol compounds were separated within ~14 min. All tea types contained all the catechins, at varying concentrations, but not all the theaflavins were present in all the tea types. This indicates that the theaflavin composition reflects the degree of the fermentation and could be used for discrimination among different types of tea. All the green tea samples contained all eight catechins; however, the concentrations of these compounds varied among the tea samples. Principal component analysis and hierarchical cluster analysis were useful for discrimination of samples. It has been unclear whether the variations of chemical components are useful for forensic discrimination. Our results demonstrate that, in addition to identification of tea varieties, catechins and theaflavins can be used for the discrimination of bottled tea samples. [ABSTRACT FROM AUTHOR]

To investigate the protective effect and mechanism of theaflavin-3,3'-O-digallate (TFDG) on vascular endothelial injury and inflammation in rats with diabetes mellitus, diabetic rats were made by high fat feed and streptozotocin injection and then divided into model group (CON), 5 mg·kg-1 and 10 mg·kg-1 TFDG intervention group (TFDG5 and TFDG10). The normal rats were taken as control group (NC). After 8 weeks of treatment, the pathological changes of abdominal aorta were observed. Plasma IL-6, IL-1β and TNF-α were detected by ELISA. The protein expression was detected by Western blot. Compared with CON, TFDG administration has no significant effects on body weight and fasting blood glucose. Pathological sections show that the injury of aorta tissue in TFDG group was improved compared with that in CON group. At the same time, the level of plasma inflammatory factors was significantly decreased, the level of plasma NO was significantly increased, and the level of MDA in aorta tissue was decreased in TFDG group. Further studies show that TFDG could down-regulate NLRP3, caspase-1 and IL-1β expressions in the aorta of diabetic rats. TFDG effectively protected vascular endothelial injury and inhibit inflammatory response in diabetic rats, and its mechanism might be through down-regulation of NLRP3 inflammatory pathway. [ABSTRACT FROM AUTHOR]

The plant Camellia sinensis is the source of different teas (white, green, yellow, oolong, black, and pu-ehr) consumed worldwide, which are classified by the oxidation degree of their bioactive compounds. The sensory (taste, aroma, and body of the drink) and functional properties of teas are affected by the amount of methylxanthines (caffeine and theobromine), amino acids (l-theanine) and reducing sugars in their composition. Additionally, flavan-3-ols, mainly characterized by epicatechins, catechins, and their derivatives, represent on average, 60% of the bioactive compounds in teas. These secondary metabolites from teas are widely recognized for their antioxidant, anti-cancer, and anti-inflammatory properties. Thus, Camellia sinensis extracts and their isolated compounds have been increasingly used by the food industry. However, bioactive compounds are very susceptible to the oxidation caused by processing and degradation under physiological conditions of gastrointestinal digestion. In this context, new approaches/technologies have been developed for the preservation of these compounds. This review presents the main stages involved in production of Camellia sinensis teas following a description of their main bioactive compounds, biological properties, stability and bioaccessibility. Besides, and updated view of Camellia sinensis teas in the field of food science and technology was provided by focusing on novel findings and innovations published in scientific literature over the last five years.

The in vivo anti-hyperglycemic effect of non-absorbable theaflavins, polyphenolic ingredients of black tea, was evaluated in spontaneously diabetic Torii (SDT) rats. A mixture of theaflavins (25 mg/kg/day) was administered to 8-week (wk)-old SDT rats for 20 weeks, showing to improve the impaired glucose tolerance of 22-wk old pre-diabetic SDT rats in both an oral glucose tolerance test and in a plasma insulin evaluation. At 28-wk diabetic SDT rats presented with increased fasting blood glucose levels (139 ± 23 mg/dL), and the intake of the theaflavins significantly (p

Fu G, Wang H, Cai Y, Zhao H, Fu W. Drug Des Devel Ther. 2018;12:1609–1619. The Editor and Publisher of Drug Design, Development and Therapy wish to retract the published article. Concerns were raised regarding the alleged duplication of western blot bands in Figure 3D. The authors explained that an error had been made by the journal which led to the unintended duplication of the Caspase-1 and IL-1β bands in Figure 3D. The journal accepts an error was made, however further investigation found the authors were unable to provide adequate original western blot data and could no longer verify the validity of the reporting findings. The decision was made to retract the article and the authors do not agree with this. We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as “Retracted”. This retraction relates to this paper

In black tea beverage, the interaction between theaflavins (TFs) and proteins may lead to the precipitates' formation, affecting its clarity and shelf life. This study investigated interactions between TF and five exogenous proteins (β -lactoglobulin (β -Lg), zein, soy protein isolate, gelatin and collagen) by spectrometry measurements. The technique for order preference by similarity to an ideal solution (TOPSIS) was applied to select the optimal protein and TF concentration to prepare a high-TF tea beverage with high clarity. The results showed TF interact with forementioned proteins via static quenching process and the optimal combination was β -Lg:200 mg/L and TF:200 mg/L. Noticeably, the selected TF concentration (200 mg/L) was 1.5 times higher than that of commercial tea beverage (80 mg/L). To obtain further insight of β -Lg-TF complexes, UV–visible absorption and Circular dichroism spectroscopy were used to investigate the secondary structures changes in β -Lg and molecular docking demonstrated the binding modes and main interaction forces of TF- β -Lg. • The quenching mechanism of five proteins by TF is static, respectively. • The optimal solution (TF of 200 mg/L with β -Lg) was selected by TOPSIS method. • The selected TF concentration of 200 mg/L is much higher than that of commercial tea beverage. • Hydrophobic interaction and hydrogen bond were main binding forces of TF - β -Lg. [ABSTRACT FROM AUTHOR]