Theaflavin derivatives in black tea and catechin derivatives in green tea inhibit HIV-1 entry by targeting gp41

Effect of polyphenols against complications of COVID-19: current evidence and potential efficacy

The COVID-19 pandemic that started in 2019 and resulted in significant morbidity and mortality continues to be a significant global health challenge, characterized by inflammation, oxidative stress, and immune system dysfunction.. Developing therapies for preventing or treating COVID-19 remains an important goal for pharmacology and drug development research. Polyphenols are effective against various viral infections and can be extracted and isolated from plants without losing their therapeutic potential. Researchers have developed methods for separating and isolating polyphenols from complex matrices. Polyphenols are effective in treating common viral infections, including COVID-19, and can also boost immunity. Polyphenolic-based antiviral medications can mitigate SARS-CoV-2 enzymes vital to virus replication and infection. Individual polyphenolic triterpenoids, flavonoids, anthraquinonoids, and tannins may also inhibit the SARS-CoV-2 protease. Polyphenol pharmacophore structures identified to date can explain their action and lead to the design of novel anti-COVID-19 compounds. Polyphenol-containing mixtures offer the advantages of a well-recognized safety profile with few known severe side effects. However, studies to date are limited, and further animal studies and randomized controlled trials are needed in future studies. The purpose of this study was to review and present the latest findings on the therapeutic impact of plant-derived polyphenols on COVID-19 infection and its complications. Exploring alternative approaches to traditional therapies could aid in developing novel drugs and remedies against coronavirus infection.

Epigallocatechin Gallate: A Multifaceted Molecule for Neurological Disorders and Neurotropic Viral Infections

Epigallocatechin-3-gallate (EGCG), a polyphenolic moiety found in green tea extracts, exhibits pleiotropic bioactivities to combat many diseases including neurological ailments. These neurological diseases include Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. For instance, in the case of Alzheimer's disease, the formation of a β-sheet in the region of the 10th-21st amino acids was significantly reduced in EGCG-induced oligomeric samples of Aβ40. Its interference induces the formation of Aβ structures with an increase in intercenter-of-mass distances, reduction in interchain/intrachain contacts, reduction in β-sheet propensity, and increase in α-helix. Besides, numerous neurotropic viruses are known to instigate or aggravate neurological ailments. It exerts an effect on the oxidative damage caused in neurodegenerative disorders by acting on GSK3-β, PI3K/Akt, and downstream signaling pathways via caspase-3 and cytochrome-c. EGCG also diminishes these viral-mediated effects, such as EGCG delayed HSV-1 infection by blocking the entry for virions, inhibitory effects on NS3/4A protease or NS5B polymerase of HCV and potent inhibitor of ZIKV NS2B-NS3pro/NS3 serine protease (NS3-SP). It showed a reduction in the neurotoxic properties of HIV-gp120 and Tat in the presence of IFN-γ. EGCG also involves numerous viral-mediated inflammatory cascades, such as JAK/STAT. Nonetheless, it also inhibits the Epstein-Barr virus replication protein (Zta and Rta). Moreover, it also impedes certain viruses (influenza A and B strains) by hijacking the endosomal and lysosomal compartments. Therefore, the current article aims to describe the importance of EGCG in numerous neurological diseases and its inhibitory effect against neurotropic viruses.

Liposomal Epigallocatechin-3-Gallate for the Treatment of Intestinal Dysbiosis in Children with Autism Spectrum Disorder: A Comprehensive Review

Autism Spectrum Disorder (ASD) is characterized by varying degrees of difficulty in social interaction and communication. These deficits are often associated with gastrointestinal symptoms, indicating alterations in both intestinal microbiota composition and metabolic activities. The intestinal microbiota influences the function and development of the nervous system. In individuals with ASD, there is an increase in bacterial genera such as Clostridium, as well as species involved in the synthesis of branched-chain amino acids (BCAA) like Prevotella copri. Conversely, decreased amounts of Akkermansia muciniphila and Bifidobacterium spp. are observed. Epigallocatechin-3-gallate (EGCG) is one of the polyphenols with the greatest beneficial activity on microbial growth, and its consumption is associated with reduced psychological distress. Therefore, the objective of this review is to analyze how EGCG and its metabolites can improve the microbial dysbiosis present in ASD and its impact on the pathology. The analysis reveals that EGCG inhibits the growth of pathogenic bacteria like Clostridium perfringens and Clostridium difficile. Moreover, it increases the abundance of Bifidobacterium spp. and Akkermansia spp. As a result, EGCG demonstrates efficacy in increasing the production of metabolites involved in maintaining epithelial integrity and improving brain function. This identifies EGCG as highly promising for complementary treatment in ASD.

Effect of EGCG Extracted from Green Tea against Largemouth Bass Virus Infection

(1) Background: Largemouth bass virus (LMBV) is a major viral pathogen in largemouth bass (Micropterus salmoides) aquaculture that often causes high mortality and heavy economic losses, thus developing treatments to combat this pathogen is of great commercial importance. Green tea is a well-known medicinal plant that contains active ingredients with antiviral, antibacterial, and other biological activities. The goals of this study were to explore the effect and mechanism of green tea source compounds on LMBV and provide data to serve as the basis for the screening of targeted drugs in the future. In this study, we evaluated the effects of the main component of green tea, epigallocatechin-3-gallate (EGCG), against LMBV infection. (2) Methods: The safe working concentration of EGCG was identified by cell viability detection and light microscopy. The antiviral activity and mechanism of action of EGCG against LMBV infection were evaluated with light microscopy, an aptamer 6-carboxy-fluorescein-based fluorescent molecular probe, and reverse transcription quantitative PCR. (3) Results: The safe working concentration of EGCG was ≤10 μg/mL. EGCG showed significant anti-LMBV infection activity in a concentration-dependent manner, and it also destroyed the structure of virus particles. EGCG impacted the binding of virus particles to cell receptors and virus invasion into the host cells. Inhibitory effects of EGCG on LMBV particles, LMBV binding to the host-cell membrane, and LMBV invasion were 84.89%, 98.99%, and 95.23%, respectively. Meanwhile, the effects of EGCG subsequently were verified in vivo. The fatality rate of the LMBV + EGCG group was significantly lower than that of the LMBV group. (4) Conclusions: Our results suggest that EGCG has effective antiviral properties against LMBV and may be a candidate for the effective treatment and control of LMBV infections in largemouth bass aquaculture.

Clinical Potential of Himalayan Herb Bergenia ligulata: An Evidence-Based Study

Herbal products have been used in traditional systems of medicine and by ethnic healers for ages to treat various diseases. Currently, it is estimated that about 80% of people worldwide use herbal traditional medicines against various ailments, partly due to easy accessibility and low cost, and the lower side effects they pose. Bergenia ligulata, a herb ranging from the Himalayas to the foothills, including the north-eastern states of India, has traditionally been used as a remedy against various diseases, most prominently kidney stones. The medicinal properties of B. ligulata have been attributed to bergenin, its most potent bioactive component. Apart from bergenin, the other compounds available in B. ligulata are arbutin, gallic acid, protocatechuic acid, chlorogenic acid, syringic acid, catechin, ferulic acid, afzelechin, paashaanolactone, caryophyllene, 1,8-cineole, β-eudesmol, stigmasterol, β-sitosterol, parasorbic acid, 3-methyl-2-buten-1-ol, phytol, terpinen-4-ol, tannic acid, isovalaric acid, avicularin, quercetin, reynoutrin, and sitoinoside I. This review summarizes various medicinal properties of the herb, along with providing deep insight into its bioactive molecules and their potential roles in the amelioration of human ailments. Additionally, the possible mechanism(s) of action of the herb's anti-urolithiatic, antioxidative, antipyretic, anti-diabetic, anti-inflammatory and hepatoprotective properties are discussed. This comprehensive documentation will help researchers to better understand the medicinal uses of the herb. Further studies on B. ligulata can lead to the discovery of new drug(s) and therapeutics for various ailments.

Broad-spectrum antiviral activity of Spatholobus suberectus Dunn against SARS-CoV-2, SARS-CoV-1, H5N1, and other enveloped viruses

The current COVID-19 pandemic caused by SARS-Cov-2 is responsible for more than 6 million deaths globally. The development of broad-spectrum and cost-effective antivirals is urgently needed. Medicinal plants are renowned as a complementary approach in which antiviral natural products have been established as safe and effective drugs. Here, we report that the percolation extract of Spatholobus suberectus Dunn (SSP) is a broad-spectrum viral entry inhibitor against SARS-CoV-1/2 and other enveloped viruses. The viral inhibitory activities of the SSP were evaluated by using pseudotyped SARS-CoV-1 and 2, HIV-1_{ADA and HXB2} , and H5N1. SSP effectively inhibited viral entry and with EC₅₀ values ranging from 3.6 to 5.1 μg/ml. Pre-treatment of pseudovirus or target cells with SSP showed consistent inhibitory activities with the respective EC₅₀ value of 2.3 or 2.1 μg/ml. SSP blocked both SARS-CoV-2 spike glycoprotein and the host ACE2 receptor. In vivo studies indicated that there was no abnormal toxicity and behavior in long-term SSP treatment. Based on these findings, we concluded that SSP has the potential to be developed as a drug candidate for preventing and treating COVID-19 and other emerging enveloped viruses.

Methylxanthines as Potential Inhibitor of SARS-CoV-2: an In Silico Approach

The aim of the present study was to test the binding affinity of methylxanthines (caffeine/theine, methylxanthine, theobromine, theophylline and xanthine) to three potential target proteins namely Spike protein (6LZG), main protease (6LU7) and nucleocapsid protein N-terminal RNA binding domain (6M3M) of SARS-CoV-2. Proteins and ligand were generated using AutoDock 1.5.6 software. Binding affinity of methylxanthines with SARS-CoV-2 target proteins was determined using Autodock Vina. MD simulation of the best interacting complexes was performed using GROMACS 2018.3 (in duplicate) and Desmond program version 2.0 (academic version) (in triplicate) to study the stabile interaction of protein-ligand complexes. Among the selected methylxanthines, theophylline showed the best binding affinity with all the three targets of SARS-CoV-2 (6LZG - 5.7 kcal mol-1, 6LU7 - 6.5 kcal mol-1, 6M3M - 5.8 kcal mol-1). MD simulation results of 100 ns (in triplicate) showed that theophylline is stable in the binding pockets of all the selected SARS-CoV-2 proteins. Moreover, methylxanthines are safer and less toxic as shown by high LD50 value with Protox II software as compared to drug chloroquine. This research supports the use of methylxanthines as a SARS-CoV-2 inhibitor. It also lays the groundwork for future studies and could aid in the development of a treatment for SARS-CoV-2 and related viral infections.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40495-021-00276-3.

Multi-Target Approaches of Epigallocatechin-3-O-gallate (EGCG) and its Derivatives Against Influenza Viruses

Influenza viruses (INFV), Orthomyxoviridae family, are mainly transmitted among humans, via aerosols or droplets from the respiratory secretions. However, fomites could be a potential transmission pathway. Annually, seasonal INFV infections account for 290-650 thousand deaths worldwide. Currently, there are two classes of approved drugs to treat INFV infections, being neuraminidase (NA) inhibitors and blockers of matrix-2 (M2) ion channel. However, cases of resistance have been observed for both chemical classes, reducing the efficacy of treatment. The emergence of influenza outbreaks and pandemics calls for new antiviral molecules more effective and that could overcome the current resistance to anti-influenza drugs. In this context, polyphenolic compounds are found in various plants and these have displayed different multi-target approaches against diverse pathogens. Among these, green tea (Camellia sinensis) catechins, in special epigallocatechin-3-O-gallate (EGCG), have demonstrated significant activities against the two most relevant human INFV, subtypes A and lineages B. In this sense, EGCG has been found a promising multi-target agent against INFV since can act inhibiting NA, hemagglutination (HA), RNA-dependent RNA polymerase (RdRp), and viral entry/adsorption. In general, the lack of knowledge about potential multi-target natural products prevents an adequate exploration of them, increasing the time for developing multi-target drugs. Then, this review aimed to compile to most relevant studies showing the anti-INFV effects of EGCG and its derivatives, which could become antiviral drug prototypes in the future.

Flavanols from Nature: A Phytochemistry and Biological Activity Review

Flavanols, a common class of secondary plant metabolites, exhibit several beneficial health properties by acting as antioxidant, anticarcinogen, cardioprotective, anti-microbial, anti-viral, and neuroprotective agents. Furthermore, some flavanols are considered functional ingredients in dairy products. Based on their structural features and health-promoting functions, flavanols have gained the attention of pharmacologists and botanists worldwide. This review collects and summarizes 121 flavanols comprising four categories: flavan-3-ols, flavan-4-ols, isoflavan-4-ols, and flavan-3,4-ols. The research of the various structural features and pharmacological activities of flavanols and their derivatives aims to lay the groundwork for subsequent research and expect to provide mentality and inspiration for the research. The current study provides a starting point for further research and development.

Enhancement of Cluster Differentiation Antigen 4 and the Body Mass Index in Patients with HIV

<b>Background and Objective:</b> The HIV is the virus that can cause AIDS by attacking white blood cells such as T cells CD4<sup>+</sup>. This study aimed to determine the relationship between antiretroviral (ARV) drugs and supplements of black tea (<i>Camellia sinensis</i> var. <i>assamica</i>) powder to increase the CD4 and Body Mass Index (BMI) in patients with HIV. <b>Materials and Methods:</b> This study used a quasi-experiment. From the average number of 10 patient visits every month in the period of January to March, 2021 in the outpatient clinic for patients diagnosed positive with HIV-AIDS, seventy patients were enlisted and divided into 2 groups from 12 districts, 35 groups intervention received ARV drugs and supplements steeping black tea powder form as much as 1,505 mg, equivalent to 5-7 glasses a 1,000-1,400 mL/day for 24 weeks, while the control group of patients received ARV drugs, standard diet each house and nutrition education. <b>Results:</b> This study showed a BMI before the intervention control group's 1st week 19.31±2.17 and after the intervention for 24 weeks, a BMI of 18.78±2.42. CD4 levels before the intervention, the 1st week were 380.57±78.63 and after the intervention for 24 weeks, 365.74±81.13 in this case either BMI or CD4 did not experience significant improvements. While the intervention group before the intervention 1st week BMI was 21.61±3.32 and after the intervention for 24 weeks, 22.2±3.19 or increased significantly (p = 0.002) and the levels of CD4 in the 1st week before the intervention, 360.91±221.20 and after the intervention for 24 weeks, 425.14±178.87 or increased significantly (p = 0.003). <b>Conclusion:</b> The ARV therapy and black tea powder significantly increased levels of CD4 and BMI HIV sufferers through the improvement of the status of T-cell immunity and body mass index.

Theaflavin Chemistry and Its Health Benefits

Huge epidemiological and clinical studies have confirmed that black tea is a rich source of health-promoting ingredients, such as catechins and theaflavins (TFs). Furthermore, TF derivatives mainly include theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), and theaflavin-3,3'-digallate (TF3). All of these TFs exhibit extensive usages in pharmaceutics, foods, and traditional medication systems. Various indepth studies reported that how TFs modulates health effects in cellular and molecular mechanisms. The available literature regarding the pharmacological activities of TFs has revealed that TF3 has remarkable anti-inflammatory, antioxidant, anticancer, antiobesity, antiosteoporotic, and antimicrobial properties, thus posing significant effects on human health. The current manuscript summarizes both the chemistry and various pharmacological effects of TFs on human health, lifestyle or aging associated diseases, and populations of gut microbiota. Furthermore, the biological potential of TFs has also been focused to provide a deeper understanding of its mechanism of action.

Nanotechnology Applications of Flavonoids for Viral Diseases

Recent years have witnessed the emergence of several viral diseases, including various zoonotic diseases such as the current pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Other viruses, which possess pandemic-causing potential include avian flu, Ebola, dengue, Zika, and Nipah virus, as well as the re-emergence of SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome) coronaviruses. Notably, effective drugs or vaccines against these viruses are still to be discovered. All the newly approved vaccines against the SARS-CoV-2-induced disease COVID-19 possess real-time possibility of becoming obsolete because of the development of ‘variants of concern’. Flavonoids are being increasingly recognized as prophylactic and therapeutic agents against emerging and old viral diseases. Around 10,000 natural flavonoid compounds have been identified, being phytochemicals, all plant-based. Flavonoids have been reported to have lesser side effects than conventional anti-viral agents and are effective against more viral diseases than currently used anti-virals. Despite their abundance in plants, which are a part of human diet, flavonoids have the problem of low bioavailability. Various attempts are in progress to increase the bioavailability of flavonoids, one of the promising fields being nanotechnology. This review is a narrative of some anti-viral dietary flavonoids, their bioavailability, and various means with an emphasis on the nanotechnology system(s) being experimented with to deliver anti-viral flavonoids, whose systems show potential in the efficient delivery of flavonoids, resulting in increased bioavailability.

An Overview on the Potential Roles of EGCG in the Treatment of COVID-19 Infection

Coronavirus disease-19 (COVID-19) pandemic is currently ongoing worldwide and causes a lot of deaths in many countries. Although different vaccines for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection have been developed and are now available, there are no effective antiviral drugs to treat the disease, except for Remdesivir authorized by the US FDA to counteract the emergency. Thus, it can be useful to find alternative therapies based on the employment of natural compounds, with antiviral features, to circumvent SARS-CoV-2 infection. Pre-clinical studies highlighted the antiviral activities of epigallocatechin-3-gallate (EGCG), a catechin primarily found in green tea, against various viruses, including SARS-CoV-2. In this review, we summarize this experimental evidence and highlight the potential use of EGCG as an alternative therapeutic choice for the treatment of SARS-CoV-2 infection.

Previously published ethno-pharmacological reports reveal the potentiality of plants and plant-derived products used as traditional home remedies by Bangladeshi COVID-19 patients to combat SARS-CoV-2

Several plants have traditionally been used since antiquity to treat various gastroenteritis and respiratory symptoms similar to COVID-19 outcomes. The common symptoms of COVID-19 include fever or chills, cold, cough, flu, headache, diarrhoea, tiredness/fatigue, sore throat, loss of taste or smell, asthma, shortness of breath, or difficulty breathing, etc. This study aims to find out the plants and plant-derived products which are being used by the COVID-19 infected patients in Bangladesh and how those plants are being used for the management of COVID-19 symptoms. In this study, online and partially in-person survey interviews were carried out among Bangladeshi respondents. We selected Bangladeshi COVID-19 patients who were detected Coronavirus positive (+) by RT-PCR nucleic acid test and later recovered. Furthermore, identified plant species from the surveys were thoroughly investigated for safety and efficacy based on the previous ethnomedicinal usage reports. Based on the published data, they were also reviewed for their significant potentialities as antiviral, anti-inflammatory, and immunomodulatory agents. We explored comprehensive information about a total of 26 plant species, belonging to 23 genera and 17 different botanical families, used in COVID-19 treatment as home remedies by the respondents. Most of the plants and plant-derived products were collected directly from the local marketplace. According to our survey results, greatly top 5 cited plant species measured as per the highest RFC value are Camellia sinensis (1.0) > Allium sativum (0.984) > Azadirachta indica (0.966) > Zingiber officinale (0.966) > Syzygium aromaticum (0.943). Previously published ethnomedicinal usage reports, antiviral, anti-inflammatory, and immunomodulatory activity of the concerned plant species also support our results. Thus, the survey and review analysis simultaneously reveals that these reported plants and plant-derived products might be promising candidates for the treatment of COVID-19. Moreover, this study clarifies the reported plants for their safety during COVID-19 management and thereby supporting them to include in any future pre-clinical and clinical investigation for developing herbal COVID-19 therapeutics.

In vitro virucidal activity of the theaflavin-concentrated tea extract TY-1 against influenza A virus

The annual spread of influenza A virus (IAV) infection is a global concern. We examined the IAV-inactivating potential of theaflavin-concentrated tea extract TY-1, which contains abundant polyphenols, including concentrated theaflavins and catechins. TY-1 exhibited concentration- and time-dependent virucidal activity against IAV. Specifically, 5.0 mg/mL TY-1 induced a 1.33 and ≥ 5.17 log₁₀ 50% tissue culture infective dose/mL reduction of the viral titer compared with dextrin as the diluent control within 30 min and 6 h reaction time, respectively. The high virucidal activity of TY-1 was attributed to the combined additive activities of multiple virucidal components, including theaflavins, which led to an investigation of the virucidal mechanism of action of TY-1. Western blotting revealed that TY-1 treatment reduced the band intensity of hemagglutinin and induced the appearance of additional high molecular mass bands/ladders. In addition, TY-1 treatment also reduced the band intensity of neuraminidase (NA). A hemagglutination assay revealed that TY-1 reduced hemagglutination activity, and an NA assay revealed reduced NA activity. These results indicated that TY-1 caused structural abnormalities in IAV spike proteins, possibly leading to their destruction. Reverse transcription polymerase chain reaction (PCR) targeting the IAV genome and electron microscopic observation of viral particles revealed that upon application of TY-1, the PCR products dissipated, which indicates that TY-1 destroyed the IAV genome, and the number of viral particles reduced. Overall, TY-1 exhibited multiple modes of IAV-inactivating activity. Our findings support the possible future practical use of TY-1 as a virucidal supplemental agent that can contribute to IAV infection control.

Advancing urban ethnopharmacology: a modern concept of sustainability, conservation and cross-cultural adaptations of medicinal plant lore in the urban environment

The discipline 'urban ethnopharmacology' emerged as a collection of traditional knowledge, ancient civilizations, history and folklore being circulated since generations, usage of botanical products, palaeobotany and agronomy. Non-traditional botanical knowledge increases the availability of healthcare and other essential products to the underprivileged masses. Intercultural medicine essentially involves 'practices in healthcare that bridge indigenous medicine and western medicine, where both are considered as complementary'. A unique aspect of urban ethnopharmacology is its pluricultural character. Plant medicine blossomed due to intercultural interactions and has its roots in major anthropological events of the past. Unani medicine was developed by Khalif Harun Al Rashid and Khalif Al Mansur by translating Greek and Sanskrit works. Similarly, Indo-Aryan migration led to the development of Vedic culture, which product is Ayurveda. Greek medicine reached its summit when it travelled to Egypt. In the past few decades, ethnobotanical field studies proliferated, especially in the developed countries to cope with the increasing demands of population expansion. At the same time, sacred groves continued to be an important method of conservation across several cultures even in the urban aspect. Lack of scientific research, validating the efficiency, messy applications, biopiracy and slower results are the main constrains to limit its acceptability. Access to resources and benefit sharing may be considered as a potential solution. Indigenous communities can copyright their traditional formulations and then can collaborate with companies, who have to provide the original inventors with a fair share of the profits since a significant portion of the health economy is generated by herbal medicine. Search string included the terms 'Urban' + 'Ethnopharmacology', which was searched in Google Scholar to retrieve the relevant literature. The present review aims to critically analyse the global concept of urban ethnopharmacology with the inherent plurality of the cross-cultural adaptations of medicinal plant use by urban people across the world.

Theaflavin-3'-O-gallate a Black-tea Constituent Blocked SARS CoV-2 RNA dependant RNA Polymerase Active-site with Better Docking Results than Remdesivir

BACKGROUND

Replication of SARS-CoV-2 depends on viral RNA-dependent RNA-polymerase (RdRp). Remdesivir, the broad-spectrum RdRp inhibitor acts as nucleoside-analogues (NAs). Remdesivir has initially been repurposed as a promising drug against SARS-CoV-2 infection with some health hazards like liver damage, allergic reaction, low blood-pressure, and breathing-shortness, throat-swelling. In comparison, theaflavin-3'-O-gallate (TFMG), the abundant black tea component has gained importance in controlling viral infection. TFMG is a non-toxic, non-invasive, antioxidant, anticancer and antiviral molecule.

RESULTS

Here, we analyzed the inhibitory effect of theaflavin-3'-O-gallate on SARS CoV-2 RdRp in comparison with remdesivir by molecular-docking study. TFMG has been shown more potent in terms of lower Atomic-Contact-Energy (ACE) and higher occupancy of surface area; -393.97 Kcal/mol and 771.90 respectively, favoured with lower desolvation-energy; -9.2:  Kcal/mol. TFMG forms more rigid electrostatic and H-bond than remdesivir. TFMG showed strong affinity to RNA primer and template and RNA passage-site of RdRp.

CONCLUSIONS

TFMG can block the catalytic residue, NTP entry site, cation binding site, nsp7-nsp12 junction with binding energy of -6. 72 Kcal/mol with Ki value of 11.79, and interface domain with binding energy of -7.72 and -6.16 Kcal/mol with Ki value of 2.21 and 30.71 µM. And most importantly, TFMG shows antioxidant/anti-inflammatory/antiviral effect on human studies.

Severe Acute Respiratory Syndrome Coronavirus-2 Inactivation Activity of the Polyphenol-Rich Tea Leaf Extract with Concentrated Theaflavins and Other Virucidal Catechins

Since severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is producing a large number of infections and deaths globally, the development of supportive and auxiliary treatments is attracting increasing attention. Here, we evaluated SARS-CoV-2-inactivation activity of the polyphenol-rich tea leaf extract TY-1 containing concentrated theaflavins and other virucidal catechins. The TY-1 was mixed with SARS-CoV-2 solution, and its virucidal activity was evaluated. To evaluate the inhibition activity of TY-1 in SARS-CoV-2 infection, TY-1 was co-added with SARS-CoV-2 into cell culture media. After 1 h of incubation, the cell culture medium was replaced, and the cells were further incubated in the absence of TY-1. The viral titers were then evaluated. To evaluate the impacts of TY-1 on viral proteins and genome, TY-1-treated SARS-CoV-2 structural proteins and viral RNA were analyzed using western blotting and real-time RT-PCR, respectively. TY-1 showed time- and concentration-dependent virucidal activity. TY-1 inhibited SARS-CoV-2 infection of cells. The results of western blotting and real-time RT-PCR suggested that TY-1 induced structural change in the S2 subunit of the S protein and viral genome destruction, respectively. Our findings provided basic insights in vitro into the possible value of TY-1 as a virucidal agent, which could enhance the current SARS-CoV-2 control measures.

Antiviral Effects of Green Tea EGCG and Its Potential Application against COVID-19

(–)-Epigallocatechin-3-O-gallate (EGCG), the most abundant component of catechins in tea (Camellia sinensis (L.) O. Kuntze), plays a role against viruses through inhibiting virus invasiveness, restraining gene expression and replication. In this paper, the antiviral effects of EGCG on various viruses, including DNA virus, RNA virus, coronavirus, enterovirus and arbovirus, were reviewed. Meanwhile, the antiviral effects of the EGCG epi-isomer counterpart (+)-gallocatechin-3-O-gallate (GCG) were also discussed.

Natural Phytochemicals as Novel Therapeutic Strategies to Prevent and Treat Parkinson's Disease: Current Knowledge and Future Perspectives

Parkinson's disease (PD) is the second-most common neurodegenerative chronic disease affecting both cognitive performance and motor functions in aged people. Yet despite the prevalence of this disease, the current therapeutic options for the management of PD can only alleviate motor symptoms. Research has explored novel substances for naturally derived antioxidant phytochemicals with potential therapeutic benefits for PD patients through their neuroprotective mechanism, targeting oxidative stress, neuroinflammation, abnormal protein accumulation, mitochondrial dysfunction, endoplasmic reticulum stress, neurotrophic factor deficit, and apoptosis. The aim of the present study is to perform a comprehensive evaluation of naturally derived antioxidant phytochemicals with neuroprotective or therapeutic activities in PD, focusing on their neuropharmacological mechanisms, including modulation of antioxidant and anti-inflammatory activity, growth factor induction, neurotransmitter activity, direct regulation of mitochondrial apoptotic machinery, prevention of protein aggregation via modulation of protein folding, modification of cell signaling pathways, enhanced systemic immunity, autophagy, and proteasome activity. In addition, we provide data showing the relationship between nuclear factor E2-related factor 2 (Nrf2) and PD is supported by studies demonstrating that antiparkinsonian phytochemicals can activate the Nrf2/antioxidant response element (ARE) signaling pathway and Nrf2-dependent protein expression, preventing cellular oxidative damage and PD. Furthermore, we explore several experimental models that evaluated the potential neuroprotective efficacy of antioxidant phytochemical derivatives for their inhibitory effects on oxidative stress and neuroinflammation in the brain. Finally, we highlight recent developments in the nanodelivery of antioxidant phytochemicals and its neuroprotective application against pathological conditions associated with oxidative stress. In conclusion, naturally derived antioxidant phytochemicals can be considered as future pharmaceutical drug candidates to potentially alleviate symptoms or slow the progression of PD. However, further well-designed clinical studies are required to evaluate the protective and therapeutic benefits of phytochemicals as promising drugs in the management of PD.

Antiviral activity of green tea and black tea polyphenols in prophylaxis and treatment of COVID-19: A review

BACKGROUND

The rapid spread of novel coronavirus called SARS-CoV-2 or nCoV has caused countries all over the world to impose lockdowns and undertake stringent preventive measures. This new positive-sense single-stranded RNA strain of coronavirus spreads through droplets of saliva and nasal discharge.

PURPOSE

US FDA has authorized the emergency use of Remdesivir looking at the increasing number of cases of COVID-19, however there is still no drug approved to treat COVID-19. An alternative way of treatment could be the use of naturally derived molecules with known antiviral properties.

METHOD

We reviewed the antiviral activities of two polyphenols derived from tea, epigallocatechin-3-gallate (EGCG) from green tea and theaflavins from black tea. Both green tea and black tea polyphenols have been reported to exhibit antiviral activities against various viruses, especially positive-sense single-stranded RNA viruses.

RESULTS

Recent studies have revealed the possible binding sites present on SARS-CoV-2 and studied their interactions with tea polyphenols. EGCG and theaflavins, especially theaflavin-3,3'-digallate (TF3) have shown a significant interaction with the receptors under consideration in this review. Some docking studies further emphasize on the activity of these polyphenols against COVID-19.

CONCLUSION

This review summarizes the available reports and evidences which support the use of tea polyphenols as potential candidates in prophylaxis and treatment of COVID-19.

Evaluation of antityrosinase activity and mechanism, antioxidation, and UV filter properties of theaflavin

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.

A Review on the Biological Activity of Camellia Species

Medicinal plants have been used since antiquity to cure illnesses and injuries. In the last few decades, natural compounds extracted from plants have garnered the attention of scientists and the Camellia species are no exception. Several species and cultivars are widespread in Asia, namely in China, Japan, Vietnam and India, being also identified in western countries like Portugal. Tea and oil are the most valuable and appreciated Camellia subproducts extracted from Camellia sinensis and Camellia oleifera, respectively. The economic impact of these species has boosted the search for additional information about the Camellia genus. Many studies can be found in the literature reporting the health benefits of several Camellia species, namely C. sinensis, C. oleifera and Camellia japonica. These species have been highlighted as possessing antimicrobial (antibacterial, antifungal, antiviral) and antitumoral activity and as being a huge source of polyphenols such as the catechins. Particularly, epicatechin (EC), epigallocatechin (EGC), epicatechin-3-gallate (ECG), and specially epigallocatechin-3-gallate (EGCG), the major polyphenols of green tea. This paper presents a detailed review of Camellia species’ antioxidant properties and biological activity.

Black tea bioactives as inhibitors of multiple targets of SARS-CoV-2 (3CLpro, PLpro and RdRp): a virtual screening and molecular dynamic simulation study

The global pandemic due to the novel Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has taken more than a million lives. Lack of definitive vaccine/drugs against this highly contagious virus has accelerated exploratory research on novel natural and synthetic inhibitors. Tea is a rich source of bioactives and known to have antiviral properties. In this study, an in silico strategy involving ADMET property screening, receptor-ligand docking and molecular dynamic (MD) simulation was employed to screen potential tea bio-active inhibitors against three selected targets (RdRp, 3CLpro and PLpro) of SARS-CoV-2. Among the 70 tea bioactives screened, theaflavin 3,3'-di-gallate (TF3), Procyanidin B2 and Theaflavin 3-gallate (TF2a) exhibited highest binding affinities towards RdRp, 3CLpro/Mpro and PLpro targets of SARS-CoV-2 with low docking scores of -14.92, -11.68 and -10.90 kcal/mol, respectively. All of them showed a substantial number of hydrogen bonds along with other interactions in and around the active sites. Interestingly, the top bioactives in our study showed higher binding affinities compared with known antiviral drugs. Further, the top protein-ligand complexes showed less conformational changes during binding when subjected to MD simulation for 100 nanoseconds. The MMPBSA results revealed that RdRp-TF3, 3CLpro-Procyanidin B2 and PLpro-TF2a complexes were stable with binding free energies of -93.59 ± 43.97, -139.78 ± 16.51 and -96.88 ± 25.39 kJ/mol, respectively. Our results suggest that theaflavin 3,3'-digallate, Theaflavin 3-gallate and Procyanidin B2 found in black tea have the potential to act as inhibitors for selected targets of SARS-CoV-2 and can be considered as drug candidates in future studies against COVID-19.

Therapeutic Potential of EGCG, a Green Tea Polyphenol, for Treatment of Coronavirus Diseases

Epigallocatechin gallate (EGCG) is a major catechin found in green tea, and there is mounting evidence that EGCG is potentially useful for the treatment of coronavirus diseases, including coronavirus disease 2019 (COVID-19). Coronaviruses encode polyproteins that are cleaved by 3CL protease (the main protease) for maturation. Therefore, 3CL protease is regarded as the main target of antivirals against coronaviruses. EGCG is a major constituent of brewed green tea, and several studies have reported that EGCG inhibits the enzymatic activity of the coronavirus 3CL protease. Moreover, EGCG has been reported to regulate other potential targets, such as RNA-dependent RNA polymerase and the viral spike protein. Finally, recent studies have demonstrated that EGCG treatment interferes with the replication of coronavirus. In addition, the bioavailability of EGCG and future research prospects are discussed.

(-)-Epigallocatechin-3-Gallate Inhibits the Life Cycle of Pseudorabies Virus In Vitro and Protects Mice Against Fatal Infection

A newly emerged pseudorabies virus (PRV) variant with enhanced pathogenicity has been identified in many PRV-vaccinated swine in China since 2011. The PRV variant has caused great economic cost to the swine industry, and measures for the effective prevention and treatment of this PRV variant are still lacking. (–)-Epigallocatechin-3-gallate (EGCG) exhibits antiviral activity against diverse viruses and thus in this study, we investigated the anti-PRV activity of EGCG in vitro and in vivo. EGCG significantly inhibited infectivity of PRV Ra and PRV XJ5 strains in PK15 B6 cells and Vero cells. The anti-PRV activity of EGCG was dose-dependent, and 50 μM EGCG could completely block viral infection at different multiplicities of infection. We next revealed that EGCG blocked PRV adsorption and entry to PK15 B6 cells in a dose-dependent manner, but inhibition of PRV entry by EGCG was not as efficient as its inhibition of PRV adsorption. PRV replication was suppressed in PK15 B6 cells treated with EGCG post-infection. However, EGCG did not affect PRV assembly and could promote PRV release. Furthermore, 40 mg/kg EGCG provided 100% protection in BALB/c mice challenged with PRV XJ5, when EGCG was administrated both pre- and post-challenge. These results revealed that EGCG exhibits antiviral activity against PRV mainly by inhibiting virus adsorption, entry and replication in vitro. Meanwhile, EGCG increased the survival of mice challenged with PRV. Therefore, EGCG might be a potential antiviral agent against PRV infection.

Antileishmanial Activity of Lignans, Neolignans, and Other Plant Phenols

Secondary metabolites (SM) from organisms have served medicinal chemists over the past two centuries as an almost inexhaustible pool of new drugs, drug-like skeletons, and chemical probes that have been used in the "hunt" for new biologically active molecules with a "beneficial effect on human mind and body." Several secondary metabolites, or their derivatives, have been found to be the answer in the quest to search for new approaches to treat or even eradicate many types of diseases that oppress humanity. A special place among SM is occupied by lignans and neolignans. These phenolic compounds are generated biosynthetically via radical coupling of two phenylpropanoid monomers, and are known for their multitarget activity and low toxicity. The disadvantage of the relatively low specificity of phenylpropanoid-based SM turns into an advantage when structural modifications of these skeletons are made. Indeed, phenylpropanoid-based SM previously have proven to offer great potential as a starting point in drug development. Compounds such as Warfarin^® (a coumarin-based anticoagulant) as well as etoposide and teniposide (podophyllotoxin-based anticancer drugs) are just a few examples. At the beginning of the third decade of the twenty-first century, the call for the treatment of more than a dozen rare or previously "neglected" diseases remains for various reasons unanswered. Leishmaniasis, a neglected disease that desperately needs new ways of treatment, is just one of these. This disease is caused by more than 20 leishmanial parasites that are pathogenic to humans and are spread by as many as 800 sandfly species across subtropical areas of the world. With continuing climate changes, the presence of Leishmania parasites and therefore leishmaniasis, the disease caused by these parasites, is spreading from previous locations to new areas. Thus, leishmaniasis is affecting each year a larger proportion of the world's population. The choice of appropriate leishmaniasis treatment depends on the severity of the disease and its form of manifestation. The success of current drug therapy is often limited, due in most cases to requiring long hospitalization periods (weeks to months) and the toxicity (side effects) of administered drugs, in addition to the increasing resistance of the parasites to treatment. It is thus important to develop new drugs and treatments that are less toxic, can overcome drug resistance, and require shorter periods of treatment. These aspects are especially important for the populations of developing countries. It was reported that several phenylpropanoid-based secondary metabolites manifest interesting antileishmanial activities and are used by various indigenous people to treat leishmaniasis. In this chapter, the authors shed some light on the various biological activities of phenylpropanoid natural products, with the main focus being on their possible applications in the context of antileishmanial treatment.

Flavonoids and Related Members of the Aromatic Polyketide Group in Human Health and Disease: Do They Really Work?

Some aromatic polyketides such as dietary flavonoids have gained reputation as miraculous molecules with preeminent beneficial effects on human health, for example, as antioxidants. However, there is little conclusive evidence that dietary flavonoids provide significant leads for developing more effective drugs, as the majority appears to be of negligible medicinal importance. Some aromatic polyketides of limited distribution have shown more interesting medicinal properties and additional research should be focused on them. Combretastatins, analogues of phenoxodiol, hepatoactive kavalactones, and silymarin are showing a considerable promise in the advanced phases of clinical trials for the treatment of various pathologies. If their limitations such as adverse side effects, poor water solubility, and oral inactivity are successfully eliminated, they might be prime candidates for the development of more effective and in some case safer drugs. This review highlights some of the newer compounds, where they are in the new drug pipeline and how researchers are searching for additional likely candidates.

The antiviral and coronavirus-host protein pathways inhibiting properties of herbs and natural compounds - Additional weapons in the fight against the COVID-19 pandemic?

Introduction

As of March 11th, 2020, the World Health Organization declared the COVID-19 outbreak a pandemic. Articles published after the SARS-CoV-1 (2002) epidemic suggest that the use of an herbal-drug integrative medical approach could have contributed to a lower fatality rate and a more rapid response in controlling the outbreak.

Methods

Pubmed was searched for articles that investigated the antiviral properties and mechanisms of action of herbs or natural compounds against the SARS-coronavirus (CoV).

Results

Forty-three (43) relevant papers were located. A general count rendered 450+ herbs and natural compounds with antiviral properties against the SARS-CoV and related viruses. From the 43 articles, thirty-one (31) uncovered the mechanisms of action of the natural substances able to oppose the coronavirus.

Discussion

A series of herbs and natural compounds demonstrated moderate to strong antiviral activity. Research on many herbs-natural compounds also showed potent and significant inhibition of CoV-host protein pathways responsible for different phases of viral replication specifically targeting 3CL^PRO, PL^PRO, RdRp, helicase protein, S protein, N protein, 3a protein, Cathepsin L, Nsp1, Nsp3c, and ORF7a, and the S protein/ACE-2 interaction.

Conclusion

The herbs-natural compounds with antiviral activity and that caused inhibition/blockade of the CoV-host protein pathways are potential therapeutic candidates. The homology between the SARS-CoV-1 and SARS-CoV-2 is around 80%. Thus, effective herbs-compounds for the former would likely be beneficial for the latter also depending on target protein similarities between the viruses. Here we provide the mechanistic bases supporting an integrative approach that includes natural compounds to fight coronavirus infections.

Structure-Activity-Relationship and Mechanistic Insights for Anti-HIV Natural Products

Acquired Immunodeficiency Syndrome (AIDS), which chiefly originatesfroma retrovirus named Human Immunodeficiency Virus (HIV), has impacted about 70 million people worldwide. Even though several advances have been made in the field of antiretroviral combination therapy, HIV is still responsible for a considerable number of deaths in Africa. The current antiretroviral therapies have achieved success in providing instant HIV suppression but with countless undesirable adverse effects. Presently, the biodiversity of the plant kingdom is being explored by several researchers for the discovery of potent anti-HIV drugs with different mechanisms of action. The primary challenge is to afford a treatment that is free from any sort of risk of drug resistance and serious side effects. Hence, there is a strong demand to evaluate drugs derived from plants as well as their derivatives. Several plants, such as Andrographis paniculata, Dioscorea bulbifera, Aegle marmelos, Wistaria floribunda, Lindera chunii, Xanthoceras sorbifolia and others have displayed significant anti-HIV activity. Here, weattempt to summarize the main results, which focus on the structures of most potent plant-based natural products having anti-HIV activity along with their mechanisms of action and IC50 values, structure-activity-relationships and important key findings.

Antioxidant potential of theaflavin ameliorates the activities of key enzymes of glucose metabolism in high fat diet and streptozotocin - induced diabetic rats

Objectives: The present study was to evaluate the effect of theaflavin on the activities of key enzymes of carbohydrate metabolism in high fat diet and streptozotocin – induced diabetic rats.

Methods: Diabetes was induced in male albino Wistar rats by feeding them with high fat diet comprising of standard laboratory rat chow 84.3%, lard 5%, egg yolk powder 10%, cholesterol 0.2% and bile salt 0.5% for 2 weeks. After 2 weeks, the animals were kept in an overnight fast and injected with low dose of streptozotocin (40 mg/kg b.w).

Results: Theaflavin (100 mg/kg b.w /day) was administered orally to diabetic rats for 30 days. At the end of the experimental period, diabetic control rats showed significant increase in plasma glucose, homeostatic model assessment of insulin resistance (HOMA-IR), glycosylated hemoglobin (HbA1c) with concomitant decrease in plasma insulin, total hemoglobin and body weight. The activities of key enzymes of carbohydrate metabolism, lipid peroxidation markers, antioxidant enzymes, glycogen content and glycogen synthase and glycogen phosphorylase were also altered in diabetic rats.

Discussion: Oral administration of theaflavin to diabetic rats significantly ameliorated all the biochemical alterations to near normal levels. The results of the present study suggest that theaflavin exhibits antidiabetic effect through its antioxidant activity.

Evaluation of Phytopolyphenols for their gp120-CD4 Binding Inhibitory Properties by In Silico Molecular Modelling & In Vitro Cell Line Studies

Background:

Lack of effective early-stage HIV-1 inhibitor instigated the need for screening of novel gp120-CD4 binding inhibitor. Polyphenols, a secondary metabolite derived from natural sources are reported to have broad spectrum HIV-1 inhibitory activity. However, the gp120-CD4 binding inhibitory activity of polyphenols has not been analysed in silico yet.

Objectives:

To establish the usage of phytopolyphenols (Theaflavin, Epigallocatechin (EGCG), Ellagic acid and Gallic acid) as early stage HIV-1 inhibitor by investigating their binding mode in reported homology of gp120-CD4 receptor complex using in silico screening studies and in vitro cell line studies.

Methods:

The in silico molecular docking and molecular simulation studies were performed using Schrödinger 2013-2 suite installed on Fujitsu Celsius Workstation. The in vitro cell line studies were performed in the TZM-bl cell line using MTT assay and β-galactosidase assay.

Results:

The results of molecular docking indicated that Theaflavin and EGCG exhibited high XP dock score with binding pose exhibiting Van der Waals interaction and hydrophobic interaction at the deeper site in the Phe43 cavity with Asp368 and Trp427. Both Theaflavin and EGCG form a stable complex with the prepared HIV-1 receptor and their binding mode interaction is within the vicinity 4 Å. Further, in vitro cell line studies also confirmed that Theaflavin (SI = 252) and EGCG (SI = 138) exert better HIV-1 inhibitory activity as compared to Ellagic acid (SI = 30) and Gallic acid (SI = 34).

Conclusions:

The results elucidate a possible binding mode of phytopolyphenols, which pinpoints their plausible mechanism and directs their usage as early stage HIV-1 inhibitor.

LDH hybrid thermosensitive hydrogel for intravaginal delivery of anti-HIV drugs

Microbicides based on hydrogel have become an effective way to prevent the HIV replication and transmission because of their convenience and prolonging drug release. In this study, a hybrid thermo-sensitive hydrogel constituted by nanosized layered double hydroxides and poloxamer 407 (P407) was constructed and co-loaded with both hydrophobic and hydrophilic drug. The LDH-P407 hydrogel could achieve sol-gel transition at body temperature. The in vivo experiment showed that LDH-P407 hydrogel can achieve controlled release of theaflavin and Nile red (hydrophobic drug model) into blood by vaginal drug delivery, meanwhile the hydrogel showed barely mucosal irritation. In addition, ex vivo experiment showed that the nifeviroc-loaded LDH-P407 hydrogel was able to specifically bind co-receptor CCR5 of DCs cells. Therefore, the LDH-P407 hydrogel would be a promising carrier for intravaginal delivery of anti-HIV drugs.

Protective effect of theaflavin on glycoprotein components and TCA cycle enzymes in high-fat diet and streptozotocin-induced diabetic rats

BACKGROUND

Theaflavins are major polyphenols in black tea which is the most widely consumed tea in the world. They possess a broad spectrum of biological activities, such as antioxidant, anti-tumor, anti-inflammatory, and cardio-protective effects. The present study was aimed to evaluate the protective effect of theaflavin on glycoprotein content and tricorboxylic acid cycle enzymes in high-fat diet and streptozotocin-induced diabetic rats as there was no study on this aspect. Diabetes was induced in male albino Wistar rats by feeding them with high-fat diet and injecting them intraperitoneally with streptozotocin (40 mg/kg b.wt).

RESULTS

Different doses of theaflavin (25, 50, and 100 mg/kg b.wt /day) were administered orally to high-fat diet and streptozotocin-induced diabetic rats for 30 days for fixing the glucose lowering dose. However, the dose at 100 mg/kg b.wt showed a significant reduction in the levels of plasma glucose and Homeostatic Model Assessment of Insulin Resistance with concomitant elevation of insulin when compared to the other two doses (25 and 50 mg/kg b.wt). Hence, 100 mg/kg b.wt was fixed as an effective dose and used for further analysis. Theaflavin administration restored the altered glycosylated hemoglobin, hemoglobin and glycoproteins (Hexose, hexosamine, fucose, and sialic acid) and TCA cycle enzymes (isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase) near the normal levels by correcting hyperglycemia. Improved histological changes were observed in the pancreas of diabetic rats upon treatment with theaflavin which supported the biochemicals investigated.

CONCLUSION

The effect produced by the theaflavin on various parameters was comparable to that of metformin-a reference antidiabetic drug. These findings suggest that theaflavin can replace the commercial drugs which could lead to reduction in toxicity and side effect caused by the later as well as reduce the secondary completions.

Antimicrobial Activities of Tea Polyphenol on Phytopathogens: A Review

The use of natural antimicrobial compounds in crop production has gained much attention from consumers and the agricultural industry. Consequently, interest in more natural, non-synthetic antimicrobials as potential alternatives to conventional chemical pesticides to combat phytopathogens has heightened. Tea polyphenol (TP), a unique and highly important functional component of tea plants, has been reported to possess antimicrobial properties against a wide spectrum of plant pathogens. The aim of this review is to discuss the emerging findings on the mechanisms of antimicrobial action, and the antimicrobial properties of TP, including their major components, effectiveness, and synergistic effects. More studies, particularly field studies, are still necessary to establish conclusive evidence for the effectiveness of TP against phytopathogens. However, the basic conclusion from existing studies suggests that TP is a potential antimicrobial agent for pesticide reduction in agricultural systems.

Gp41 inhibitory activity prediction of theaflavin derivatives using ligand/structure-based virtual screening approaches

Gp41 and its conserved hydrophobic groove on the NHR region is one of the attractive targets in the design of HIV-1 entry inhibitory agents. This hydrophobic pocket is very critical for the progression of HIV and host cell fusion. In this study different ligand-based (structure similarity search) and structure-based (molecular docking and molecular dynamic simulation) methods were performed in a virtual screening procedure to select the best compounds with the most probable HIV-1 gp41 inhibitory activities. In silico pharmacokinetics and ADMET (absorption, distribution, metabolism, excretion and toxicity) properties filtration also was considered to choose the compounds with best drug-like properties. The results of molecular docking and molecular dynamic simulations of the final selected compounds showed suitable stabilities of their complexes with gp41. The final selected hits could have better pharmacokinetics properties than the template compound, theaflavin digallate (TF₃), a naturally-originated potent gp41 inhibitor.

Theaflavins Improve Memory Impairment and Depression-Like Behavior by Regulating Microglial Activation

Inflammation in the brain is associated with various disorders including Alzheimer's disease and depression. Thus, inflammation has received increasing attention regarding preventive approaches to such disorders. Epidemiological investigations have reported that drinking tea reduces the risk of dementia and depression. Theaflavins, a polyphenol found in black tea, are known to have anti-oxidative and anti-inflammation effects, but the effects of theaflavins on cognitive decline and depression induced by inflammation have not been investigated. To address this research gap, the present study assessed whether theaflavins could protect synapses and dendrites damaged by inflammation and prevent concomitant memory impairment and depression-like behavior in mice. Intracerebroventricular injection with lipopolysaccharide (LPS) induces neural inflammation associated with reduced spontaneous alternations in the Y-maze test and increased immobility in the tail suspension test, indicating impaired spatial memory and depression-like behavior, respectively. Oral administration with theaflavins prevented these behavioral changes induced by LPS. Theaflavins also suppressed productions of inflammatory cytokines and prevented dendritic atrophy and spine loss in the brain. Notably, theaflavins have a stronger anti-inflammatory effect than other polyphenols such as catechin, chlorogenic acid, and caffeic acid. These results suggest that theaflavins can suppress neural inflammation and prevent the symptoms of inflammation-related brain disorders.

Theaflavins prevent cartilage degeneration via AKT/FOXO3 signaling in vitro

Theaflavins (TFs) are the main bioactive polyphenols in tea and contribute to protection against oxidative stress. Excessive reactive oxygen species (ROS) accumulation can lead to the disruption of cartilage homeostasis. The present study examined the potential effects of TFs on H₂O₂-induced cartilage degeneration in vitro. Cell Counting kit (CCK-8) was used to determine cell viability, and flow cytometric analysis was used to detect ROS, apoptosis and DNA damage. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to detect the expression levels of target factors. The present study revealed that TFs effectively reduced the expression of catabolic factors, including matrix metalloproteinase-13, interleukin-1 and cartilage glycoprotein 39. TFs inhibited ROS generation in cartilage degeneration, and suppressed apoptosis and DNA damage caused by oxidative stress. TFs also downregulated the expression levels of cleaved caspase-3 and B-cell lymphoma 2-associated X protein, and the DNA damage-related genes, ATR serine/threonine kinase and ATM serine/threonine kinase. Furthermore, TFs enhanced the activity of glutathione peroxidase 1 and catalase, but reduced the expression levels of phosphorylated (p)-AKT serine/threonine kinase (AKT) and p-Forkhead box O3 (FOXO3)a. Conversely, the effects of TFs on apoptosis and DNA damage were reversed by persistent activation of AKT. In conclusion, TFs prevented cartilage degeneration via AKT/FOXO3 signaling in vitro. The present study suggested that TFs may be a potential candidate drug for the prevention of cartilage degeneration.

Investigation of the inhibition effect of arachidonic acid on the core structure of the HIV-1 gp41

The gp41 transmembrane domain of the envelope glycoprotein of the human immunodeficiency virus (HIV) modulates the conformation of the viral envelope spike. During the HIV fusion process, C-terminal heptad repeat (CHR, C34) wrap antiparallel to the N-terminal heptad repeat (NHR, N36) helices to form a stable six-helix bundle (6-HB) core structure, which brings the viral and cell membranes into close proximity for fusion. Therefore, inhibiting the formation of 6-HB is considered to be a key activity of an effective HIV-1 fusion inhibitor. The level of arachidonic acid (AA) is increased in HIV infected patients. Our study provides a new insight into the functional role of AA during the formation of HIV-1 gp41 6-HB. Native polyacrylamide gel electrophoresis (N-PAGE), enzyme-linked-immunosorbent serologic assay (ELISA) and circular dichroism (CD) spectroscopy were used to investigate the inhibition of AA for the formation of 6-HB. Molecular docking technique was adopted to explore the underlying mechanism. HIV-1 JR-FL (R5 strain) Envelope was adopted to determine the inhibition effect of AA. AA is shown to interfere with the formation of α-helical complexes of N36 and C34 by N-PAGE, ELISA and CD spectroscopy. The isotherm titration microcalorimetry (ITC) results indicate there is a single class of binding site on N36. ΔH and ΔS are -12.43 kJ mol^-1 and 70.07 J mol^-1 K^-1, respectively, indicating hydrophobic interaction and electrostatic forces are the main acting forces. The molecular docking results manifest that AA interacts with the hydrophobic residues (Trp-571, Leu-568, Val-570 and Leu-576) and ionic interactions occur between Arg-579 and the -COOH of AA. The inhibitory activity of AA on HIV-1 JR-FL is quantified by 50% effective concentration (EC₅₀) and 90% effective concentration (EC₉₀), which are 31.42 ± 1.08 and 133.47 ± 18.10 μg mL^-1, respectively. All the results indicate that AA is able to inhibit the formation of 6-HB but cannot disrupt the preformed 6-HB. Therefore, AA is a potential inhibitor for the viral fusion/entry.

Theaflavins, polyphenols of black tea, inhibit entry of hepatitis C virus in cell culture

The treatment of hepatitis C virus (HCV) infection by combination of direct acting antivirals (DAA), with different mode of action, has made substantial progress in the past few years. However, appearance of resistance and high cost of the therapy is still an obstacle in the achievement of the therapy, more specifically in developing countries. In this context, search for affordable antivirals with new mechanisms of action is still needed. Tea, after water, is the most popular drink worldwide. Polyphenols extracted from green tea have already shown anti-HCV activity as entry inhibitors. Here, three different theaflavins, theaflavin (TF1), theaflavin-3’-monogallate (TF2), and theaflavin-3-3’-digallate (TF3), which are major polyphenols from black tea, were tested against HCV in cell culture. The results showed that all theaflavins inhibit HCV infection in a dose-dependent manner in an early step of infection. Results obtained with HCV pseudotyped virions confirmed their activity on HCV entry and demonstrated their pan-genotypic action. No effect on HCV replication was observed by using HCV replicon. Investigation on the mechanism of action of black tea theaflavins showed that they act directly on the virus particle and are able to inhibit cell-to-cell spread. Combination study with inhibitors most widely used in anti-HCV treatment regimen demonstrated that TF3 exerts additive effect. In conclusion, theaflavins, that are present in high quantity in black tea, are new inhibitors of HCV entry and hold promise for developing in therapeutic arsenal for HCV infection.

Antiviral Mechanism of Action of Epigallocatechin-3-O-gallate and Its Fatty Acid Esters

Epigallocatechin-3-O-gallate (EGCG) is the major catechin component of green tea (Cameria sinensis), and is known to possess antiviral activities against a wide range of DNA viruses and RNA viruses. However, few studies have examined chemical modifications of EGCG in terms of enhanced antiviral efficacy. This paper discusses which steps of virus infection EGCG interferes with, citing previous reports. EGCG appears most likely to inhibits the early stage of infections, such as attachment, entry, and membrane fusion, by interfering with viral membrane proteins. According to the relationships between structure and antiviral activity of catechin derivatives, the 3-galloyl and 5'-OH group of catechin derivatives appear critical to antiviral activities. Enhancing the binding affinity of EGCG to virus particles would thus be important to increase virucidal activity. We propose a newly developed EGCG-fatty acid derivative in which the fatty acid on the phenolic hydroxyl group would be expected to increase viral and cellular membrane permeability. EGCG-fatty acid monoesters showed improved antiviral activities against different types of viruses, probably due to their increased affinity for virus and cellular membranes. Our study promotes the application of EGCG-fatty acid derivatives for the prevention and treatment of viral infections.

Trilobatin as an HIV-1 entry inhibitor targeting the HIV-1 Gp41 envelope

HIV-1 transmembrane protein gp41 plays a crucial role by forming a stable six-helix bundle during HIV entry. Due to highly conserved sequence of gp41, the development of an effective and safe small-molecule compound targeting gp41 is a good choice. Currently, natural polyanionic ingredients with anti-HIV activities have aroused concern. Here, we first discovered that a glycosylated dihydrochalcone, trilobatin, exhibited broad anti-HIV-1 activity and low cytotoxicity in vitro. Site-directed mutagenesis analysis suggested that the hydrophobic residue (I564) located in gp41 pocket-forming site is pivotal for anti-HIV activity of trilobatin. Furthermore, trilobatin displayed synergistic anti-HIV activities combined with other antiretroviral agents. Trilobatin has a good potential to be developed as a small-molecule HIV-1 entry inhibitor for clinical combination therapy.

Neuroprotective Effects and Mechanisms of Tea Bioactive Components in Neurodegenerative Diseases

As the population ages, neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease (AD) impose a heavy burden on society and families. The pathogeneses of PD and AD are complex. There are no radical cures for the diseases, and existing therapeutic agents for PD and AD have diverse side effects. Tea contains many bioactive components such as polyphenols, theanine, caffeine, and theaflavins. Some investigations of epidemiology have demonstrated that drinking tea can decrease the risk of PD and AD. Tea polyphenols can lower the morbidity of PD and AD by reducing oxidative stress and regulating signaling pathways and metal chelation. Theanine can inhibit the glutamate receptors and regulate the extracellular concentration of glutamine, presenting neuroprotective effects. Additionally, the neuroprotective mechanisms of caffeine and theaflavins may contribute to the ability to antagonize the adenosine receptor A2AR and the antioxidant properties, respectively. Thus, tea bioactive components might be useful for neuronal degeneration treatment in the future. In the present paper, the neuro protection and the mechanisms of tea and its bioactive components are reviewed. Moreover, the potential challenges and future work are also discussed.

Addition of milk to tea infusions: Helpful or harmful? Evidence from in vitro and in vivo studies on antioxidant properties

Tea consumption is practised as a tradition, and has shown potential to improve human health. Maximal uptake of tea antioxidants and milk proteins without a negative impact on tea flavor is highly desired by consumers. There is a conflicting evidence of the effect of milk addition to tea on antioxidant activity. Differences in the type of tea, the composition, type and amount of milk, preparation method of tea-milk infusions, the assays used to measure antioxidant activity, and sampling size likely account for different findings. Interactions between tea polyphenols and milk proteins, especially between catechins and caseins, could account for a decrease in antioxidant activity, although other mechanisms are also possible, given the similar effects between soy and bovine milk. The role of milk fat globules and the milk fat globule membrane surface is also important when considering interactions and loss of polyphenolic antioxidant activity, which has not been addressed in the literature.

Theaflavin ameliorates ionizing radiation-induced hematopoietic injury via the NRF2 pathway

It has been well established that reactive oxygen species (ROS) play a critical role in ionizing radiation (IR)-induced hematopoietic injury. Theaflavin (TF), a polyphenolic compound from black tea, has been implicated in the regulation of endogenous cellular antioxidant systems. However, it remains unclear whether TF could ameliorate IR-induced hematopoietic injury, particularly the hematopoietic stem cell (HSC) injury. In this study, we explored the potential role of TF in IR-induced HSC injury and the underlying mechanism in a total body irradiation (TBI) mouse model. Our results showed that TF improved survival of irradiated wild-type mice and ameliorated TBI-induced hematopoietic injury by attenuating myelosuppression and myeloid skewing, increasing HSC frequency, and promoting reconstitution of irradiated HSCs. Furthermore, TF inhibited TBI-induced HSC senescence. These effects of TF were associated with a decline in ROS levels and DNA damage in irradiated HSCs. TF reduced oxidative stress mainly by up-regulating nuclear factor erythroid 2-related factor 2 (NRF2) and its downstream targets in irradiated Lineage^-c-kit⁺ positive cells. However, TF failed to improve the survival, to increase HSC frequency and to reduce ROS levels of HSCs in irradiated Nrf2^-/- mice. These findings suggest that TF ameliorates IR-induced HSC injury via the NRF2 pathway. Therefore, TF has the potential to be used as a radioprotective agent to ameliorate IR-induced hematopoietic injury.

A Review of the Antiviral Role of Green Tea Catechins

Over the centuries, infectious diseases caused by viruses have seriously threatened human health globally. Viruses are responsible not only for acute infections but also many chronic infectious diseases. To prevent diseases caused by viruses, the discovery of effective antiviral drugs, in addition to vaccine development, is important. Green tea catechins (GTCs) are polyphenolic compounds from the leaves of Camelliasinensis. In recent decades, GTCs have been reported to provide various health benefits against numerous diseases. Studies have shown that GTCs, especially epigallocatechin-3-gallate (EGCG), have antiviral effects against diverse viruses. The aim of this review is to summarize the developments regarding the antiviral activities of GTCs, to discuss the mechanisms underlying these effects and to offer suggestions for future research directions and perspectives on the antiviral effects of EGCG.