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This article is a comprehensive review of the literature pertaining to the antidepressant effects and mechanisms of regular tea consumption. Meta-data supplemented with recent observational studies were first analyzed to assess the association between tea consumption and depression risk. The literature reported risk ratios (RR) were 0.69 with 95% confidence intervals of 0.62–0.77. Next, we thoroughly reviewed human trials, mouse models, and in vitro experiments to determine the predominant mechanisms underlying the observed linear relationship between tea consumption and reduced risk of depression. Current theories on the neurobiology of depression were utilized to map tea-mediated mechanisms of antidepressant activity onto an integrated framework of depression pathology. The major nodes within the network framework of depression included hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, inflammation, weakened monoaminergic systems, reduced neurogenesis/neuroplasticity, and poor microbiome diversity affecting the gut–brain axis. We detailed how each node has subsystems within them, including signaling pathways, specific target proteins, or transporters that interface with compounds in tea, mediating their antidepressant effects. A major pathway was found to be the ERK/CREB/BDNF signaling pathway, up-regulated by a number of compounds in tea including teasaponin, L-theanine, EGCG and combinations of tea catechins and their metabolites. Black tea theaflavins and EGCG are potent anti-inflammatory agents via down-regulation of NF-κB signaling. Multiple compounds in tea are effective modulators of dopaminergic activity and the gut–brain axis. Taken together, our findings show that constituents found in all major tea types, predominantly L-theanine, polyphenols and polyphenol metabolites, are capable of functioning through multiple pathways simultaneously to collectively reduce the risk of depression.

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.

The natural dietary product tea (Camellia sinensis) and its bioactive polyphenols such as epigallocatechin gallate (EGCG) and theaflavin (TF) demonstrated potential anticancer effects in different preclinical and clinical studies. The aim of the present review was to understand the molecular mechanisms of the tea and tea polyphenol-mediated cancer prevention and therapy. In the setting of in vivo cancer prevention studies, administration of the tea and tea polyphenols at preinitiation stages only showed partial prevention, whereas continuous administration showed potential effect in restriction of carcinogenesis in the body's multiple organs at early premalignant stages throughout the experiment. Similar to different in vitro cancer cell models, treatment after initiation stages showed potential therapeutic efficacy in vivo. But, the mechanisms of prevention and therapy were found to be similar regardless of tea and its polyphenols. They mainly serve as antioxidants and induce the detoxification system, thereby inhibiting carcinogen metabolism and cancer initiation. Additionally, they could inhibit self-renewal, proliferation, and survival of the tumor-initiating population in restriction of the carcinogenesis progression from cancer initiation and promotion. This might be a result of the modulation of membrane organization, interaction with DNA/RNA/proteins and epigenetic modifications, as well as regulation of cellular replicative potential by the tea polyphenols. [Display omitted] •We reviewed cancer preventive and therapeutic mechanisms by tea and tea polyphenols.•Tea and tea polyphenols could restrict the progression of carcinogenesis in vivo in the early dysplastic stages.•Tea and tea polyphenols serve as antioxidants and induce the detoxification system during restriction.•Tea and tea polyphenols inhibit self-renewal, proliferation, and survival of tumor-initiating clones.•Tea polyphenols interact with or modify different cellular targets of the membrane to nucleus.

Theaflavin has been proven to own strong antioxidative capacity; however, the molecular mechanism underlying its protective effect against cerebral ischemia-reperfusion (I/R) injury remains unclear. Therefore, the present study was designed to elucidate the neuroprotective effects of theaflavin on cerebral I/R injury and its underlying molecular mechanisms. To investigate the effects of theaflavin on neurological function, neurogenesis, and oxidative stress, experiments were performed using a cerebral I/R injury rat model, and neural stem cells (NSCs) were subjected to oxygen-glucose deprivation and reoxygenation (OGD/R). Further, the expression profiles of miRNA-128-3p and the regulatory function of nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) were evaluated in these models. We found that theaflavin treatment significantly reduced infarct volume and neuronal injury, and thus improved the impaired memory and learning ability. Furthermore, theaflavin treatment significantly enhanced the increase in NSC proliferation, reduction in the apoptotic rate and inhibition of oxidative stress. Mechanistically, theaflavin targeted miRNA-128-3p and further activated the Nrf2 pathway to reduce oxidative stress. In summary, theaflavin has a strong ability to attenuate cerebral I/R injury through miRNA-128-3p-mediated recovery of the impaired antioxidant defense system, which suggests that it could be a potential drug candidate for ischemic stroke.

Tea is the most widely used beverage worldwide. Japanese and Chinese people have been drinking tea for centuries and in Asia, it is the most consumed beverage besides water. It is a rich source of pharmacologically active molecules which have been implicated to provide diverse health benefits. The three major forms of tea are green, black and oolong tea based on the degree of fermentation. The composition of tea differs with the species, season, leaves, climate, and horticultural practices. Polyphenols are the major active compounds present in teas. The catechins are the major polyphenolic compounds in green tea, which include epigallocatechin-3-gallate (EGCG), epigallocatechin, epicatechin-3-gallate and epicatechin, gallocatechins and gallocatechin gallate. EGCG is the predominant and most studied catechin in green tea. There are numerous evidences from cell culture and animal studies that tea polyphenols have beneficial effects against several pathological diseases including cancer, diabetes and cardiovascular diseases. The polyphenolic compounds present in black tea include theaflavins and thearubigins. In this review article, we will summarize recent studies documenting the role of tea polyphenols in the prevention of cancer, diabetes, cardiovascular and neurological diseases.

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.

Outbreak of coronavirus disease 2019 occurred in Wuhan and has rapidly spread to almost all parts of world. GB-1, the herbal formula from Tian Shang Sheng Mu of Chiayi Puzi Peitian Temple, is used for the prophylaxis of SARS-CoV-2 in Taiwan. In this study, we investigated that the effect of GB-1 and the index compounds of GB-1 on the ACE2 and TMPRSS2 expression through in vitro and in vivo study. In our result, GB-1 can inhibit ACE2 and TMPRSS2 protein expression in HepG2 cells, 293T cells, and Caco-2 cells without cytotoxicity. For the mouse model, GB-1 treatment could decrease ACE2 and TMPRSS2 expression levels of the lung and kidney tissue without adverse effects, including nephrotoxicity and hepatotoxicity. In the compositions of GB-1, 0.5–1 mg/ml of Glycyrrhiza uralensis Fisch. ex DC . extract could not inhibit ACE2 mRNA and protein expression in HepG2 cells. In addition, theaflavin-3-gallate could inhibit protein expression of ACE2 and TMPRSS2 without significant cytotoxicity. Our results suggest that GB-1 and theaflavin-3-gallate could act as potential candidates for prophylaxis or treatment of SARS-CoV-2 infection through inhibiting protein expression of ACE2 and TMPRSS2 for the further study.

Continuing caution is required against the potential emergence of SARS-CoV-2 novel mutants that could pose the next global health and socioeconomical threats. If virus in saliva can be inactivated by a beverage, such a beverage may be useful because the saliva of infected persons is the major origin of droplets and aerosols that mediate human-to-human viral transmission. We previously reported that SARS-CoV-2 was significantly inactivated by treatment in vitro with tea including green tea and black tea. Catechins and its derived compounds galloylated theaflavins (gTFs) bound to the receptor-binding domain (RBD) of the S-protein and blocked interaction between RBD and ACE2. Black tea is often consumed with sugar, milk, lemon juice, etc., and it remains unclarified whether these ingredients may influence the anti-SARS-CoV-2 effect of black tea. Here, we examined the effect of black tea on Omicron subvariants in the presence of these ingredients. The infectivity of Omicron subvariants was decreased to 1/100 or lower after treatment with black tea for 10 s. One or two teaspoons of milk (4~8 mL) completely blocked the anti-viral effect of a cup of tea (125 mL), whereas an addition of sugar or lemon juice failed to do so. The suppressive effect was dose-dependently exerted by milk casein but not whey proteins. gTFs were coprecipitated with casein after acidification of milk-supplemented black tea, strongly suggesting the binding of gTFs to casein. The present study demonstrates for the first time that an addition of milk cancelled the anti-SARS-CoV-2 effect of black tea due to binding of casein to gTFs.

Potential effects of tea and its constituents on SARS-CoV-2 infection were assessed in vitro. Infectivity of SARS-CoV-2 was decreased to 1/100 to undetectable levels after a treatment with black tea, green tea, roasted green tea, or oolong tea for 1 min. An addition of (−) epigallocatechin gallate (EGCG) significantly inactivated SARS-CoV-2, while the same concentration of theasinensin A (TSA) and galloylated theaflavins including theaflavin 3,3′-di-O-gallate (TFDG) had more remarkable anti-viral activities. EGCG, TSA, and TFDG at 1 mM, 40 µM, and 60 µM, respectively, which are comparable to the concentrations of these compounds in tea beverages, significantly reduced infectivity of the virus, viral RNA replication in cells, and secondary virus production from the cells. EGCG, TSA, and TFDG significantly inhibited interaction between recombinant ACE2 and RBD of S protein. These results suggest potential usefulness of tea in prevention of person-to-person transmission of the novel coronavirus.

Theaflavins (TFs), which are polyphenolic compounds characterized by a benzotropolone structure, serve as the primary quality and health‐promoting components in black tea. Recent investigations have disclosed various health advantages linked to TFs, especially their potential to act as lead compounds in the formulation of therapeutic drugs targeting severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), positioning them as a significant area of focus within food science and nutrition research. This review initially examines the primary physiological activities, mechanisms of action, and challenges related to TFs. It subsequently details the formation mechanism of enzyme‐catalyzed TFs from catechins. Building upon this groundwork, this review assesses the recent advancements in two in vitro synthesis methods of TFs: enzymatic oxidation and nonenzymatic synthesis. Finally, the challenges that arise during the large‐scale industrial implementation of these synthesis techniques are analyzed, and research strategies aimed at mitigating these issues are suggested. The primary goal of this review was to provide insightful perspectives and guidance for prospective research and industrial utilization of TFs. Theaflavins demonstrate significant pharmacological effects on various chronic diseases, while low availability and stability. In vitro synthesis methods, such as enzymatic oxidation and nonenzymatic synthesis, can significantly enhance the production of theaflavins, but industrialization still faces some challenges. Innovative technologies such as protein engineering, genetic engineering, and biomimetic catalysis are expected to be powerful tools for addressing the industrial challenges of theaflavins.