Docking Characterization and in vitro Inhibitory Activity of Flavan-3-ols and Dimeric Proanthocyanidins Against the Main Protease Activity of SARS-Cov-2

Tea Catechins: Potential Plant-Derived Feed Additives for Improving Chicken Intestinal Health and Productivity

In response to the global antimicrobial resistance and residue issues, most countries and regions have implemented comprehensive bans on the use of growth-promoting antibiotics in animal feed formulations. Catechins are a group of polyphenolic compounds that are naturally present in many fruits and plant-derived foods, emerging as potential antibiotic-alternative additives for promoting gut health and production performance in poultry farming. The compounds demonstrate dual biological functions: mitigating oxidative tissue damage and actively remodeling gut microbiota composition by suppressing enteric pathogens (e.g., Clostridium) and enriching beneficial bacteria (e.g., Bifidobacterium). Such multifaceted regulation enhances intestinal barrier integrity, thereby improving nutrient absorption and translating into measurable production benefits, including elevated growth rates and feed conversion efficiency. The current research suggests that the added levels of catechins in chicken diets ranges from 40 to 600 mg/kg. However, the research and application of catechins in chicken production are still at the initial stage, which requires more attention worldwide and further mechanism exploration. This mini-review synthesizes recent research findings on the effects of catechins on chicken health, aiming to promote the formulation of feed additive strategies using plant-derived compounds such as catechins as substitutes for antibiotics, to maintain the health of poultry and other animals while preserving production performance.

Diverse Structures of Tea Polyphenols from Rougui Wuyi Rock Tea and Their Potential as Inhibitor of 3C-like Protease

Tea polyphenols, the primary bioactive constituents responsible for the various health benefits of tea, can be categorized into different subgroups according to their structural characteristics. However, the distinctions in antiviral activity among the diverse types of polyphenolic compounds remain unexplored. In the present study, fifty-eight tea polyphenols with varied structures, including eleven undescribed compounds, were isolated from Rougui Wuyi rock tea. Their molecular structures were elucidated using comprehensive analytical approaches of NMR, HRMS, CD spectroscopic data and acid hydrolysis. The isolated polyphenol analogs could be structurally classified into two main categories: flavan-3-ols, which include catechins, flavoalkaloids, procyanidins and theasinensins, and flavones, encompassing kaempferol, quercetin, myricetin, and their respective glycosides. The inhibitory activities of fifty-eight tea polyphenols against 3CLpro were assessed in vitro, and eighteen phenolic compounds exhibited inhibitory effects on 3CLpro, with IC50 values ranging from 9.8 μM to 61.1 μM. Among them, two types of tea polyphenols, catechin and flavoalkaloid derivatives, demonstrated superior inhibitory effects compared to other categories. The structure-activity relationship was further explored, and molecular docking analysis revealed that the differing inhibitory effects of catechin and flavoalkaloid derivatives were attributed to the variations in the number and positions of the hydrogen bond interactions with 3CLpro. This study provides a valuable understanding of tea polyphenols and supplies potential lead compounds for antiviral drugs.

Tea Catechins in Green Tea Inhibit the Activity of SARS-CoV-2 Main Protease via Covalent Adduction

We herein examined the inhibitory effects of tea catechins on the SARS-CoV-2 main protease (Mpro). Among the catechins analyzed, epigallocatechin 3-(3″-O-methyl)gallate, epigallocatechin gallate (EGCG), gallocatechin, gallocatechin gallate, and epigallocatechin inhibited recombinant Mpro in a dose-dependent manner. Peptide mapping revealed that catechins preferentially formed covalent bonds with five sequences with the strongest activity at the C145 active site. Fragmentation analysis indicated 184 cleavages from peptides containing C145, corresponding to the D ring, suggesting that the B ring was attached to C145. When 10 bottled teas were incubated with Mpro, four green teas inhibited the enzyme by over 80%, whereas the blended and barley teas showed no effect. EGCG reacted covalently with SARS-CoV-2 Mpro within cells when incubated with cultured cells expressing Mpro. This is the first study to report direct covalent binding between tea catechins and Mpro in cells. This suggests that catechins from green tea can inhibit Mpro in infected cells.

Consensus Pharmacophore Strategy For Identifying Novel SARS-Cov-2 Mpro Inhibitors from Large Chemical Libraries

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main Protease (Mpro) is an enzyme that cleaves viral polyproteins translated from the viral genome and is critical for viral replication. Mpro is a target for anti-SARS-CoV-2 drug development, and multiple Mpro crystals complexed with competitive inhibitors have been reported. In this study, we aimed to develop an Mpro consensus pharmacophore as a tool to expand the search for inhibitors. We generated a consensus model by aligning and summarizing pharmacophoric points from 152 bioactive conformers of SARS-CoV-2 Mpro inhibitors. Validation against a library of conformers from a subset of ligands showed that our model retrieved poses that reproduced the crystal-binding mode in 77% of the cases. Using models derived from a consensus pharmacophore, we screened >340 million compounds. Pharmacophore-matching and chemoinformatics analyses identified new potential Mpro inhibitors. The candidate compounds were chemically dissimilar to the reference set, and among them, demonstrating the relevance of our model. We evaluated the effect of 16 candidates on Mpro enzymatic activity finding that seven have inhibitory activity. Three compounds (1, 4, and 5) had IC50 values in the midmicromolar range. The Mpro consensus pharmacophore reported herein can be used to identify compounds with improved activity and novel chemical scaffolds against Mpro. The method developed for its generation is provided as an open-access code (https://github.com/AngelRuizMoreno/ConcensusPharmacophore) and can be applied to other pharmacological targets.

Emerging Therapeutic Potential of Polyphenols from Geranium sanguineum L. in Viral Infections, Including SARS-CoV-2

The existing literature supports the anti-inflammatory, antioxidant, and antiviral capacities of the polyphenol extracts derived from Geranium sanguineum L. These extracts exhibit potential in hindering viral replication by inhibiting enzymes like DNA polymerase and reverse transcriptase. The antiviral properties of G. sanguineum L. seem to complement its immunomodulatory effects, contributing to infection resolution. While preclinical studies on G. sanguineum L. suggest its potential effectiveness against COVID-19, there is still a lack of clinical evidence. Therefore, the polyphenols extracted from this herb warrant further investigation as a potential alternative for preventing and treating COVID-19 infections.

Identification and biosynthesis of plant papanridins, a group of novel oligomeric flavonoids

The discovery of novel flavonoids and elucidation of their biosynthesis are fundamental to understanding their roles in plants and their benefits for human and animal health. Here, we report a new pathway for polymerization of a group of novel oligomeric flavonoids in plants. We engineered red cells for discovering genes of interest involved in the flavonoid pathway and identified a gene encoding a novel flavanol polymerase (FP) localized in the central vacuole. FP catalyzes the polymerization of flavanols, such as epicatechin and catechin, to produce yellowish dimers or oligomers. Structural elucidation shows that these compounds feature a novel oligomeric flaven-flavan (FF) skeleton linked by interflavan-flaven and interflaven bonds, distinguishing them from proanthocyanidins and dehydrodicatechins. Detailed chemical and physical characterizations further confirmed the novel FFs as flavonoids. Mechanistic investigations demonstrated that FP polymerizes flavan-3-ols and flav-2-en-3-ol carbocation, forming dimeric or oligomeric flaven-4→8-flavans, which we term "papanridins." Data from transgenic experiments, mutant analysis, metabolic profiling, and phylogenetic analyses show that the biosynthesis of papanridins is prevalent in cacao, grape, blueberry, corn, rice, Arabidopsis, and other species in the plant kingdom. In summary, our study discoveries a group of novel oligomeric flavonoids, namely papanridins, and reveals that a novel FP-mediated polymerization mechanism for the biosynthesis of papanridins in plants.

Computational studies on the interaction of Omicron subvariants (BA.1, BA.2, and BA.3) with ACE2 and polyphenols

INTRODUCTION

The SARS-CoV-2 Omicron variant BA.2 is spreading widely across the globe. The World Health Organization (WHO) designated BA.2 as a variant of concern due to its high transmission rate and pathogenicity. To elucidate the structural changes caused by mutations, we conducted a comparative analysis of BA.2 with variants BA.1 and BA.3.

OBJECTIVE

In the present study, we aimed to investigate the interactions of the spike glycoprotein receptor-binding domain (SGp RBD) of Omicron variants BA.1, BA.2, and BA.3 with the human receptor hACE2. Further, a library of 233 polyphenols was screened by molecular docking with the SGp RBDs of Omicron variants BA.1, BA.2, and BA.3.

METHODS

Protein-protein and protein-ligand molecular docking simulations were performed with AutoDock Vina and the ClusPro 2.0 server, respectively. The protein-ligand interactions were evaluated by BIOVIA Discovery Studio and ChimeraX 1.4. The molecular dynamics simulations for 100 ns were performed using GROMACS 2021.

RESULTS

Compared to other variants of concern, the structural changes in Omicron caused by mutations at key positions improved its ability to cause infection. Despite multiple mutations, many important polyphenols bind effectively at the RBDs of Omicron variants, with the required pharmacokinetic and ADME features and obeying the Lipinski rule.

CONCLUSION

Even though Omicron variants have multiple mutations and their transmission rate is relatively high, the computed binding affinities of lead polyphenols like epigallocatechin-3-O-gallate (EGCG) and luteolin-7-O-glucuronide (L7G) indicate that traditional medicines and proper immunity booster diets may be useful in the long-term fight against SARS-CoV-2.

Stand Up to Stand Out: Natural Dietary Polyphenols Curcumin, Resveratrol, and Gossypol as Potential Therapeutic Candidates against Severe Acute Respiratory Syndrome Coronavirus 2 Infection

The COVID-19 pandemic has stimulated collaborative drug discovery efforts in academia and the industry with the aim of developing therapies and vaccines that target SARS-CoV-2. Several novel therapies have been approved and deployed in the last three years. However, their clinical application has revealed limitations due to the rapid emergence of viral variants. Therefore, the development of next-generation SARS-CoV-2 therapeutic agents with a high potency and safety profile remains a high priority for global health. Increasing awareness of the "back to nature" approach for improving human health has prompted renewed interest in natural products, especially dietary polyphenols, as an additional therapeutic strategy to treat SARS-CoV-2 patients, owing to its good safety profile, exceptional nutritional value, health-promoting benefits (including potential antiviral properties), affordability, and availability. Herein, we describe the biological properties and pleiotropic molecular mechanisms of dietary polyphenols curcumin, resveratrol, and gossypol as inhibitors against SARS-CoV-2 and its variants as observed in in vitro and in vivo studies. Based on the advantages and disadvantages of dietary polyphenols and to obtain maximal benefits, several strategies such as nanotechnology (e.g., curcumin-incorporated nanofibrous membranes with antibacterial-antiviral ability), lead optimization (e.g., a methylated analog of curcumin), combination therapies (e.g., a specific combination of plant extracts and micronutrients), and broad-spectrum activities (e.g., gossypol broadly inhibits coronaviruses) have also been emphasized as positive factors in the facilitation of anti-SARS-CoV-2 drug development to support effective long-term pandemic management and control.

The natural tannins oligomeric proanthocyanidins and punicalagin are potent inhibitors of infection by SARS-CoV-2

The Coronavirus Disease 2019 (COVID-19) pandemic continues to infect people worldwide. While the vaccinated population has been increasing, the rising breakthrough infection persists in the vaccinated population. For living with the virus, the dietary guidelines to prevent virus infection are worthy of and timely to develop further. Tannic acid has been demonstrated to be an effective inhibitor of coronavirus and is under clinical trial. Here we found that two other members of the tannins family, oligomeric proanthocyanidins (OPCs) and punicalagin, are also potent inhibitors against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with different mechanisms. OPCs and punicalagin showed inhibitory activity against omicron variants of SARS-CoV-2 infection. The water extractant of the grape seed was rich in OPCs and also exhibited the strongest inhibitory activities for viral entry of wild-type and other variants in vitro. Moreover, we evaluated the inhibitory activity of grape seed extractants (GSE) supplementation against SARS-CoV-2 viral entry in vivo and observed that serum samples from the healthy human subjects had suppressive activity against different variants of SARS-CoV-2 Vpp infection after taking GSE capsules. Our results suggest that natural tannins acted as potent inhibitors against SARS-CoV-2 infection, and GSE supplementation could serve as healthy food for infection prevention.

The Therapeutic Potential of Natural Dietary Flavonoids against SARS-CoV-2 Infection

The exploration of non-toxic and cost-effective dietary components, such as epigallocatechin 3-gallate and myricetin, for health improvement and disease treatment has recently attracted substantial research attention. The recent COVID-19 pandemic has provided a unique opportunity for the investigation and identification of dietary components capable of treating viral infections, as well as gathering the evidence needed to address the major challenges presented by public health emergencies. Dietary components hold great potential as a starting point for further drug development for the treatment and prevention of SARS-CoV-2 infection owing to their good safety, broad-spectrum antiviral activities, and multi-organ protective capacity. Here, we review current knowledge of the characteristics-chemical composition, bioactive properties, and putative mechanisms of action-of natural bioactive dietary flavonoids with the potential for targeting SARS-CoV-2 and its variants. Notably, we present promising strategies (combination therapy, lead optimization, and drug delivery) to overcome the inherent deficiencies of natural dietary flavonoids, such as limited bioavailability and poor stability.

Garbage in, garbage out: how reliable training data improved a virtual screening approach against SARS-CoV-2 MPro

Introduction: The identification of chemical compounds that interfere with SARS-CoV-2 replication continues to be a priority in several academic and pharmaceutical laboratories. Computational tools and approaches have the power to integrate, process and analyze multiple data in a short time. However, these initiatives may yield unrealistic results if the applied models are not inferred from reliable data and the resulting predictions are not confirmed by experimental evidence. Methods: We undertook a drug discovery campaign against the essential major protease (MPro) from SARS-CoV-2, which relied on an in silico search strategy -performed in a large and diverse chemolibrary- complemented by experimental validation. The computational method comprises a recently reported ligand-based approach developed upon refinement/learning cycles, and structure-based approximations. Search models were applied to both retrospective (in silico) and prospective (experimentally confirmed) screening. Results: The first generation of ligand-based models were fed by data, which to a great extent, had not been published in peer-reviewed articles. The first screening campaign performed with 188 compounds (46 in silico hits and 100 analogues, and 40 unrelated compounds: flavonols and pyrazoles) yielded three hits against MPro (IC₅₀ ≤ 25 μM): two analogues of in silico hits (one glycoside and one benzo-thiazol) and one flavonol. A second generation of ligand-based models was developed based on this negative information and newly published peer-reviewed data for MPro inhibitors. This led to 43 new hit candidates belonging to different chemical families. From 45 compounds (28 in silico hits and 17 related analogues) tested in the second screening campaign, eight inhibited MPro with IC₅₀ = 0.12-20 μM and five of them also impaired the proliferation of SARS-CoV-2 in Vero cells (EC₅₀ 7-45 μM). Discussion: Our study provides an example of a virtuous loop between computational and experimental approaches applied to target-focused drug discovery against a major and global pathogen, reaffirming the well-known "garbage in, garbage out" machine learning principle.

Protease inhibitors from Theobroma cacao impair SARS-CoV-2 replication in vitro

SARS-CoV-2 is a newly emerging virus from the Coronaviridae family that has already infected over 700 million people worldwide and killed over 6 million. This virus uses protease molecules to replicate and infect the host, which makes these molecules targets for therapeutic substances to eliminate the virus and treat infected people. Through the protein-protein molecular docking approach, we detected two cystatins from Theobroma cacao, TcCYS3 and TcCYS4, described as papain-like protease inhibitors. These inhibitors decreased SARS-CoV-2 genomic copies without toxicity to Vero cells. There is a need to perform comprehensive studies in relevant animal models and to investigate the action mechanisms of protease inhibitors from Theobroma cacao that control the replication of SARS-CoV-2 in human cells.

High-throughput screening and investigation of the inhibitory mechanism of α-glucosidase inhibitors in teas using an affinity selection-mass spectrometry method

An affinity selection-mass spectrometry method was applied for high-throughput screening of α-glucosidase (AGH) inhibitors from teas. Fourteen out of nineteen screened AGH inhibitor candidates were clustered as galloylated polyphenols (GPs). "AGH-GPs" interaction studies, including enzyme kinetics, fluorescence spectroscopy, circular dichroism, and molecular docking, jointly suggested that GPs noncompetitively inhibit AGH activity by interacting with amino acid residues near the active site of AGH and inducing changes in AGH secondary structure. Representative GPs and white tea extract (WTE) showed comparable AGH inhibition effects in Caco2 cells and postprandial hypoglycemic efficacy in diabetic mice as acarbose. The area under the curve of oral sucrose tolerance test was lower by 8.16%, 6.17%, and 7.37% than control group in 15 mg/kg EGCG, 15 mg/kg strictinin, and 150 mg/kg WTE group, respectively. Our study presents a high-efficiency approach to discover novel AGH inhibitors and elucidates a potential mechanism by which tea decreases diabetes risks.

Exploration of SARS-CoV-2 Mpro Noncovalent Natural Inhibitors Using Structure-Based Approaches

With the emergence of antibody-evasive omicron subvariants (BA.2.12.1, BA.4, and BA.5), which can compromise the efficacy of vaccination, it is of utmost importance to widen the finite therapeutic options for COVID-19. Although more than 600 co-crystal complexes of Mpro with inhibitors have been revealed, utilizing them to search for novel Mpro inhibitors remains limited. Although there were two major groups of Mpro inhibitors, covalent and noncovalent inhibitors, noncovalent inhibitors were our main focus due to the safety concerns with their covalent counterparts. Hence, this study aimed to explore Mpro noncovalent inhibition ability of phytochemicals extracted from Vietnamese herbals by combining multiple structure-based approaches. By closely inspecting 223 complexes of Mpro with noncovalent inhibitors, a 3D-pharmacophore model representing typical chemical features of Mpro noncovalent inhibitors was generated with good validation scores (sensitivity = 92.11%, specificity = 90.42%, accuracy = 90.65%, and goodness-of-hit score = 0.61). Afterward, the pharmacophore model was applied to explore the potential Mpro inhibitors from our in-house Vietnamese phytochemical database, revealing 18 substances, 5 of which were in vitro assayed. The remaining 13 substances were then examined by induced-fit molecular docking, revealing 12 suitable compounds. A machine-learning activity prediction model was developed to rank the hit, suggesting nigracin and calycosin-7-O-β-glucopyranoside as promising Mpro natural noncovalent inhibitors.

Therapeutic potential of green tea catechin, (-)-epigallocatechin-3-O-gallate (EGCG) in SARS-CoV-2 infection: Major interactions with host/virus proteases

BACKGROUND

The current COVID-19 pandemic from the human pathogenic virus SARS-CoV-2 has resulted in a major health hazard globally. The morbidity and transmission modality of this disease are severe and uncontrollable. As no effective clinical drugs are available for treatment of COVID-19 infection till to date and only vaccination is used as prophylaxis and its efficacy is restricted due to emergent of new variants of SARS-CoV-2, there is an urgent need for effective drugs for its treatment.

PURPOSE

The aim of this review was to provide a detailed analysis of anti-SARS-CoV-2 efficacy of (-)-epigallocatechin-3-O-gallate (EGCG), a major catechin constituent of green tea (Camellia sinensis (L.) Kuntze) beverage to highlight the scope of EGCG in clinical medicine as both prophylaxis and treatment of present COVID-19 infection. In addition, the factors related to poor oral bioavailabilty of EGCG was also analysed for a suggestion for future research in this direction.

STUDY DESIGN

We collected the published articles related to anti-SARS-CoV-2 activity of EGCG against the original strain (Wuhan type) and its newly emerged variants of SARS-CoV-2 virus.

METHODS

A systematic search on the published literature was conducted in various databases including Google Scholar, PubMed, Science Direct and Scopus to collect the relevant literature.

RESULTS

The findings of this search demonstrate that EGCG shows potent antiviral activity against SARS-CoV-2 virus by preventing viral entry and replication in host cells in vitro models. The studies on the molecular mechanisms of EGCG in inhibition of SARS-CoV-2 infection in host cells reveal that EGCG blocks the entry of the virus particles by interaction with the receptor binding domain (RBD) of viral spike (S) protein to host cell surface receptor protease angiotensin-converting enzyme 2 (ACE2) as well as suppression of the expressions of host proteases, ACE2, TMPRSS2 and GRP78, required for viral entry, by Nrf2 activation in host cells. Moreover, EGCG inhibits the activities of SARS-CoV-2 main protease (Mpro), papain-like protease (PLpro), endoribonuclease Nsp15 in vitro models and of RNA-dependent RNA polymerase (RdRp) in molecular docking model for suppression of viral replication. In addition, EGCG significantly inhibits viral inflammatory cytokine production by stimulating Nrf2- dependent host immune response in virus-infected cells. EGCG significantly reduces the elevated levels of HMGB1, a biomarker of sepsis, lung fibrosis and thrombotic complications in viral infections. EGCG potentially inhibits the infection of original (Wuhan type) strain of SARS-CoV-2 and other newly emerged variants as well as the infections of SARS-CoV-2 virus spike-protein of WT and its mutants-mediated pseudotyped viruses . EGCG shows maximum inhibitory effect against SARS-CoV-2 infection when the host cells are pre-incubated with the drug prior to viral infection. A sorbitol/lecithin-based throat spray containing concentrated green tea extract rich in EGCG content significantly reduces SARS-CoV-2 infectivity in oral mucosa. Several factors including degradation in gastrointestinal environment, low absorption in small intestine and extensive metabolism of EGCG are responsible for its poor bioavailability in humans. Pharmacokinetic and metabolism studies of EGCG in humans reveal poor bioavailability of EGCG in human plasma and EGCG-4"-sulfate is its major metabolite. The concentration of EGCG-4"-sulfate in human plasma is almost equivalent to that of free EGCG (Cmax 177.9 vs 233.5 nmol/L). These findings suggest that inhibition of sulfation of EGCG is a crucial factor for improvement of its bioavailability. In vitro study on the mechanism of EGCG sulfonation indicates that sulfotransferases, SULT1A1 and SULT1A3 are responsible for sulfonation in human liver and small intestine, respectively. Some attempts including structural modifications, and nanoformulations of EGCG and addition of nutrients with EGCG have been made to improve the bioavailability of EGCG.

CONCLUSIONS

The findings of this study suggest that EGCG has strong antiviral activity against SARS-CoV-2 infection independent of viral strains (Wuhan type (WT), other variants) by inhibition of viral entry and replication in host cells in vitro models. EGCG may be useful in reduction of this viral load in salivary glands of COVID-19 patients, if it is applied in mouth and throat wash formulations in optimal concentrations. EGCG could be a promising candidate in the development of effective vaccine for prevention of the infections of newly emergent strains of SARS-CoV-2 virus. EGCG might be useful also as a clinical medicine for treatment of COVID-19 patients if its bioavailability in human plasma is enhanced.

Botanical inhibitors of SARS-CoV-2 viral entry: a phylogenetic perspective

Throughout the SARS-CoV-2 pandemic, the use of botanical dietary supplements in the United States has increased, yet their safety and efficacy against COVID-19 remains underexplored. The Quave Natural Product Library is a phylogenetically diverse collection of botanical and fungal natural product extracts including popular supplement ingredients. Evaluation of 1867 extracts and 18 compounds for virus spike protein binding to host cell ACE2 receptors in a SARS-CoV-2 pseudotyped virus system identified 310 extracts derived from 188 species across 76 families (3 fungi, 73 plants) that exhibited ≥ 50% viral entry inhibition activity at 20 µg/mL. Extracts exhibiting mammalian cytotoxicity > 15% and those containing cardiotoxic cardiac glycosides were eliminated. Three extracts were selected for further testing against four pseudotyped variants and infectious SARS-CoV-2 and were then further chemically characterized, revealing the potent (EC50 < 5 µg/mL) antiviral activity of Solidago altissima L. (Asteraceae) flowers and Pteridium aquilinum (L.) Kuhn (Dennstaedtiaceae) rhizomes.

Phenolic Fraction from Peanut (Arachis hypogaea L.) By-product: Innovative Extraction Techniques and New Encapsulation Trends for Its Valorization

Peanut skin is a by-product rich in bioactive compounds with high nutritional and pharmaceutical values. The phenolic fraction, rich in proanthocyanidins/procyanidins, is a relevant class of bioactive compounds, which has been increasingly applied as functional ingredients for food and pharmaceutical applications and is mostly recovered from peanut skins through low-pressure extraction methods. Therefore, the use of green high-pressure extractions is an interesting alternative to value this peanut by-product. This review addresses the benefits of the phenolic fraction recovered from peanut skin, with a focus on proanthocyanin/procyanidin compounds, and discusses the improvement of their activity, bioavailability, and protection, by methods such as encapsulation. Different applications for the proanthocyanidins, in the food and pharmaceutical industries, are also explored. Additionally, high-pressure green extraction methods, combined with micro/nanoencapsulation, using wall material derived from peanut industrial processing, may represent a promising biorefinery strategy to improve the bioavailability of proanthocyanidins recovered from underutilized peanut skins.

Flavan-based phytoconstituents inhibit Mpro, a SARS-COV-2 molecular target, in silico

A well-validated in-silico approach can provide promising drug candidates for the treatment of the ongoing CoVID19 pandemic. In this study, we have screened 32 phytochemical constituents (PCCs) with Mpro binding site (PDB:6W63) based on which we identified three possible candidates that are likely to be effective against CoVID19-viz., licoleafol (binding energy: -8.1 kcal/mol), epicatechin gallate (-8.5 kcal/mol) and silibinin (-8.4 kcal/mol) that result in higher binding affinity than the known inhibitor, X77 (-7.7 kcal/mol). Molecular dynamics (MD) simulations of PCCs-Mpro complex confirmed molecular docking results with high structural and dynamical stability. The selected compounds were found to exhibit low mean squared displacements (licoleafol: 2.25 ± 0.43 Å, epicatechin gallate: 1.93 ± 0.35 Å, and silibinin: 1.39 ± 0.19 Å) and overall low fluctuations of the binding complexes (root mean squared fluctuations below 2 Å). Visualization of the MD trajectories and structural analyses revealed that they remain confined to the initial binding region, with mean fluctuations lower than 3 Å. To access the collective motion of the atoms, we performed principal component analysis demonstrating that the first 10 principal components are the major contributors (approximate contribution of 80%) and are responsible for the overall PCCs motion. Considering that the three selected PCCs share the same flavan backbone and exhibit antiviral activity against hepatitis C, we opine that licoleafol, epi-catechin gallate, and silibinin can be promising anti-CoVID19 drug candidates. Communicated by Ramaswamy H. Sarma.

Amazonian fruits with potential effects on COVID-19 by inflammaging modulation: A narrative review

The COVID-19 pandemic had a great impact on the mortality of older adults and, chronic non- transmissible diseases (CNTDs) patients, likely previous inflammaging condition that is common in these subjects. It is possible that functional foods could attenuate viral infection conditions such as SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the causal agent of COVID-19 pandemic. Previous evidence suggested that some fruits consumed by Amazonian Diet from Pre-Colombian times could present relevant proprieties to decrease of COVID-19 complications such as oxidative-cytokine storm. In this narrative review we identified five potential Amazonian fruits: açai berry (Euterpe oleracea), camu-camu (Myrciaria dubia), cocoa (Theobroma cacao), Brazil nuts (Bertholletia excelsa), and guaraná (Paullinia cupana). Data showed that these Amazonian fruits present antioxidant, anti-inflammatory and other immunomodulatory activities that could attenuate the impact of inflammaging states that potentially decrease the evolution of COVID-19 complications. The evidence compiled here supports the complementary experimental and clinical studies exploring these fruits as nutritional supplement during COVID-19 infection. PRACTICAL APPLICATIONS: These fruits, in their natural form, are often limited to their region, or exported to other places in the form of frozen pulp or powder. But there are already some companies producing food supplements in the form of capsules, in the form of oils and even functional foods enriched with these fruits. This practice is common in Brazil and tends to expand to the international market.

Molecular Docking and Dynamics Simulation of Several Flavonoids Predict Cyanidin as an Effective Drug Candidate against SARS-CoV-2 Spike Protein

The in silico method has provided a versatile process of developing lead compounds from a large database in a short duration. Therefore, it is imperative to look for vaccinations and medications that can stop the havoc caused by SARS-CoV-2. The spike protein of SARS-CoV-2 is required for the viral entry into the host cells, hence inhibiting the virus from fusing and infecting the host. This study determined the binding interactions of 36 flavonoids along with two FDA-approved drugs against the spike protein receptor-binding domain of SARS-CoV-2 through molecular docking and molecular dynamics (MD) simulations. In addition, the molecular mechanics generalized Born surface area (MM/GBSA) approach was used to calculate the binding-free energy (BFE). Flavonoids were selected based on their in vitro assays on SARS-CoV and SARS-CoV-2. Our pharmacokinetics study revealed that cyanidin showed good drug-likeness, fulfilled Lipinski's rule of five, and conferred favorable toxicity parameters. Furthermore, MD simulations showed that cyanidin interacts with spike protein and alters the conformation and binding-free energy suited. Finally, an in vitro assay indicated that about 50% reduction in the binding of hACE2 with S1-RBD in the presence of cyanidin-containing red grapes crude extract was achieved at approximately 1.25 mg/mL. Hence, cyanidin may be a promising adjuvant medication for the SARS-CoV-2 spike protein based on in silico and in vitro research.

Phytochemical drug discovery for COVID-19 using high-resolution computational docking and machine learning assisted binder prediction

The COVID-19 pandemic has resulted in millions of deaths around the world. Multiple vaccines are in use, but there are many underserved locations that do not have adequate access to them. Variants may emerge that are highly resistant to existing vaccines, and therefore cheap and readily obtainable therapeutics are needed. Phytochemicals, or plant chemicals, can possibly be such therapeutics. Phytochemicals can be used in a polypharmacological approach, where multiple viral proteins are inhibited and escape mutations are made less likely. Finding the right phytochemicals for viral protein inhibition is challenging, but in-silico screening methods can make this a more tractable problem. In this study, we screen a wide range of natural drug products against a comprehensive set of SARS-CoV-2 proteins using a high-resolution computational workflow. This workflow consists of a structure-based virtual screening (SBVS), where an initial phytochemical library was docked against all selected protein structures. Subsequently, ligand-based virtual screening (LBVS) was employed, where chemical features of 34 lead compounds obtained from the SBVS were used to predict 53 lead compounds from a larger phytochemical library via supervised learning. A computational docking validation of the 53 predicted leads obtained from LBVS revealed that 28 of them elicit strong binding interactions with SARS-CoV-2 proteins. Thus, the inclusion of LBVS resulted in a 4-fold increase in the lead discovery rate. Of the total 62 leads, 18 showed promising pharmacokinetic properties in a computational ADME screening. Collectively, this study demonstrates the advantage of incorporating machine learning elements into a virtual screening workflow.Communicated by Ramaswamy H. Sarma.

Clinical Research Progress of Small Molecule Compounds Targeting Nrf2 for Treating Inflammation-Related Diseases

Studies have found that inflammation is a symptom of various diseases, such as coronavirus disease 2019 (COVID-19) and rheumatoid arthritis (RA); it is also the source of other diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), lupus erythematosus (LE), and liver damage. Nrf2 (nuclear factor erythroid 2-related factor 2) is an important multifunctional transcription factor in cells and plays a central regulatory role in cellular defense mechanisms. In recent years, several studies have found a strong association between the activation of Nrf2 and the fight against inflammation-related diseases. A number of small molecule compounds targeting Nrf2 have entered clinical research. This article reviews the research status of small molecule compounds that are in clinical trials for the treatment of COVID-19, rheumatoid arthritis, Alzheimer's disease, Parkinson's disease, lupus erythematosus, and liver injury.

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.

The Main Protease of SARS-CoV-2 as a Target for Phytochemicals against Coronavirus

In late December 2019, the first cases of COVID-19 emerged as an outbreak in Wuhan, China that later spread vastly around the world, evolving into a pandemic and one of the worst global health crises in modern history. The causative agent was identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although several vaccines were authorized for emergency use, constantly emerging new viral mutants and limited treatment options for COVID-19 drastically highlighted the need for developing an efficient treatment for this disease. One of the most important viral components to target for this purpose is the main protease of the coronavirus (Mpro). This enzyme is an excellent target for a potential drug, as it is essential for viral replication and has no closely related homologues in humans, making its inhibitors unlikely to be toxic. Our review describes a variety of approaches that could be applied in search of potential inhibitors among plant-derived compounds, including virtual in silico screening (a data-driven approach), which could be structure-based or fragment-guided, the classical approach of high-throughput screening, and antiviral activity cell-based assays. We will focus on several classes of compounds reported to be potential inhibitors of Mpro, including phenols and polyphenols, alkaloids, and terpenoids.

Anti-SARS-CoV-2 activity of various PET-bottled Japanese green teas and tea compounds in vitro

The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a serious threat to global public health. The emergence of SARS-CoV-2 variants is a significant concern regarding the continued effectiveness of vaccines and antiviral therapeutics. Thus, natural products such as foods, drinks, and other compounds should be investigated for their potential to treat COVID-19. Here, we examined the in vitro antiviral activity against SARS-CoV-2 of various polyethylene terephthalate (PET)-bottled green Japanese teas and tea compounds. Six types of PET-bottled green tea were shown to inhibit SARS-CoV-2 at half-maximal inhibitory concentrations (IC50) of 121- to 323-fold dilution. Our study revealed for the first time that a variety of PET-bottled Japanese green tea drinks inhibit SARS-CoV-2 infection in a dilution-dependent manner. The tea compounds epigallocatechin gallate (EGCG) and epicatechin gallate showed virucidal activity against SARS-CoV-2, with IC50 values of 6.5 and 12.5 µM, respectively. The investigated teas and tea compounds inactivated SARS-CoV-2 in a dose-dependent manner, as demonstrated by the viral RNA levels and infectious titers. Furthermore, the green teas and EGCG showed significant inhibition at the entry and post-entry stages of the viral life cycle and inhibited the activity of the SARS-CoV-2 3CL-protease. These findings indicate that green tea drinks and tea compounds are potentially useful in prophylaxis and COVID-19 treatment.

Insights into acylation mechanisms: co-expression of serine carboxypeptidase-like acyltransferases and their non-catalytic companion paralogs

Serine carboxypeptidase-like acyltransferases (SCPL-ATs) play a vital role in the diversification of plant metabolites. Galloylated flavan-3-ols highly accumulate in tea (Camellia sinensis), grape (Vitis vinifera), and persimmon (Diospyros kaki). To date, the biosynthetic mechanism of these compounds remains unknown. Herein, we report that two SCPL-AT paralogs are involved in galloylation of flavan-3-ols: CsSCPL4, which contains the conserved catalytic triad S-D-H, and CsSCPL5, which has the alternative triad T-D-Y. Integrated data from transgenic plants, recombinant enzymes, and gene mutations showed that CsSCPL4 is a catalytic acyltransferase, while CsSCPL5 is a non-catalytic companion paralog (NCCP). Co-expression of CsSCPL4 and CsSCPL5 is likely responsible for the galloylation. Furthermore, pull-down and co-immunoprecipitation assays showed that CsSCPL4 and CsSCPL5 interact, increasing protein stability and promoting post-translational processing. Moreover, phylogenetic analyses revealed that their homologs co-exist in galloylated flavan-3-ol- or hydrolyzable tannin-rich plant species. Enzymatic assays further revealed the necessity of co-expression of those homologs for acyltransferase activity. Evolution analysis revealed that the mutations of the CsSCPL5 catalytic residues may have taken place about 10 million years ago. These findings show that the co-expression of SCPL-ATs and their NCCPs contributes to the acylation of flavan-3-ols in the plant kingdom.

Investigating the interaction between dietary polyphenols, the SARS CoV-2 spike protein and the ACE-2 receptor

The global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has called for an urgent need for the identification of compounds able to control, prevent or slow down the global pandemic. Several dietary polyphenols were assayed against binding to the SARS CoV-2 S1 spike protein and the human ACE-2 receptor, the target of the SARS CoV-2 virus using nano differential scanning fluorimetry, suggesting interaction of dietary polyphenols with both proteins. Following this initial screening the two dietary polyphenols with the strongest affinity were evaluated in a second functional binding assay. The assay was based on the thermophoresis of a fluorescently labelled spike protein and the ACE-2 receptor in the presence of dietary concentrations of the polyphenol in question. It could be experimentally shown that 5-caffeoyl quinic acid and epicatechin reduce the binding constant between SARS CoV-2 spike protein of the alpha variant and the ACE-2 receptor by a factor of ten. The finding could as well be applied to black tea and a coffee beverage with dietary 5-CQA concentrations for the alpha variant Spike protein. Hence it can be speculated that a cup of coffee reduces binding of the virus to its human target, therefore reducing the likelihood of infection with SARS CoV-2, acting as a virus entry-inhibitor.

Flavonols and dihydroflavonols inhibit the main protease activity of SARS-CoV-2 and the replication of human coronavirus 229E

Since December 2019, the deadly novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the current COVID-19 pandemic. To date, vaccines are available in the developed countries to prevent the infection of this virus; however, medicines are necessary to help control COVID-19. Human coronavirus 229E (HCoV-229E) causes the common cold. The main protease (Mpro) is an essential enzyme required for the multiplication of these two viruses in the host cells, and thus is an appropriate candidate to screen potential medicinal compounds. Flavonols and dihydroflavonols are two groups of plant flavonoids. In this study, we report docking simulation with two Mpro enzymes and five flavonols and three dihydroflavonols, in vitro inhibition of the SARS-CoV-2 Mpro, and in vitro inhibition of the HCoV 229E replication. The docking simulation results predicted that (+)-dihydrokaempferol, (+)- dihydroquercetin, (+)-dihydromyricetin, kaempferol, quercetin, myricentin, isoquercitrin, and rutin could bind to at least two subsites (S1, S1', S2, and S4) in the binding pocket and inhibit the activity of SARS-CoV-2 Mpro. Their affinity scores ranged from -8.8 to -7.4 (kcal/mol). Likewise, these compounds were predicted to bind and inhibit the HCoV-229E Mpro activity with affinity scores ranging from -7.1 to -7.8 (kcal/mol). In vitro inhibition assays showed that seven available compounds effectively inhibited the SARS-CoV-2 Mpro activity and their IC50 values ranged from 0.125 to 12.9 μM. Five compounds inhibited the replication of HCoV-229E in Huh-7 cells. These findings indicate that these antioxidative flavonols and dihydroflavonols are promising candidates for curbing the two viruses.

Investigation of the Azorean Camellia sinensis Processing Conditions to Maximize the Theaflavin 3,3'-di-O-Gallate Content as a Potential Antiviral Compound

The molecular constituents of Camellia sinensis, in particular epigallocatechin-3-O-gallate (EGCG) and, more remarkably, the galloylated theaflavins, mainly theaflavin-3,3'-di-O-gallate (TF-3,3'-DG), have been reported to inhibit SARS-CoV-2 3-chymotrypsin-like protease (3CLpro), an enzyme required for the cleavage of its polyproteins, to produce vital individual functional proteins for viral cell replication. Our results for total catechin content revealed the values of 174.72, 200.90, and 211.75 mg/g dry weight (DW) in spring, and the values of 183.59, 191.36, and 215.09 mg/g DW in summer, for tea plantation zones 1, 2, and 3, respectively. For the TF-3,3'-DG content, the values of 2.68, 1.13, and 3.72 mg/g DW were observed in spring, and the values of 3.78, 2.06, and 8.91 mg/g DW in summer for zones 1, 2, and 3, respectively. In the same zone, different contents of TF-3,3'-DG were observed across plucking months of April, June, and August, with values of 1.13, 2.77, and 4.18 mg/g DW, respectively, showing higher values in summer. Different values of TF-3,3'-DG contents were also observed in the same tea plantation zone but from different plant parts, revealing higher values in the bud and the first and second leaves (3.62 mg/g DW) and lower values in the third and fourth leaves (1.14 mg/g DW). The TF-3,3'-DG content increased from 3.31 to 4.98 mg/g DW with increased fermentation time from 1 to 3 h, respectively, and increased for lower temperature and longer fermentation time. The aim of this study was to investigate the processing conditions that lead to maximum TF-3,3'-DG content and, given its potential impact as an inhibitor of the 3CLpro enzyme, to create a novel antiviral Azorean black tea.

Role of Diet and Nutrients in SARS-CoV-2 Infection: Incidence on Oxidative Stress, Inflammatory Status and Viral Production

Coronavirus illness (COVID-19) is an infectious pathology generated by intense severe respiratory syndrome coronavirus 2 (SARS-CoV-2). This infectious disease has emerged in 2019. The COVID-19-associated pandemic has considerably affected the way of life and the economy in the world. It is consequently crucial to find solutions allowing remedying or alleviating the effects of this infectious disease. Natural products have been in perpetual application from immemorial time given that they are attested to be efficient towards several illnesses without major side effects. Various studies have shown that plant extracts or purified molecules have a promising inhibiting impact towards coronavirus. In addition, it is substantial to understand the characteristics, susceptibility and impact of diet on patients infected with COVID-19. In this review, we recapitulate the influence of extracts or pure molecules from medicinal plants on COVID-19. We approach the possibilities of plant treatment/co-treatment and feeding applied to COVID-19. We also show coronavirus susceptibility and complications associated with nutrient deficiencies and then discuss the major food groups efficient on COVID-19 pathogenesis. Then, we covered emerging technologies using plant-based SARS-CoV-2 vaccine. We conclude by giving nutrient and plants curative therapy recommendations which are of potential interest in the COVID-19 infection and could pave the way for pharmacological treatments or co-treatments of COVID-19.

Natural Polyphenols, 1,2,3,4,6-O-Pentagalloyglucose and Proanthocyanidins, as Broad-Spectrum Anticoronaviral Inhibitors Targeting Mpro and RdRp of SARS-CoV-2

The natural plant dietary polyphenols 1,2,3,4,6-O-Pentagalloylglucose (PGG) and proanthocyanidin (PAC) have potent antioxidant activity and a variety of pharmacological activities, including antiviral activity. In this study, we examined the inhibitory effect of PGG and PAC on SARS-CoV-2 virus infection, and elucidated its mode of action. PGG and PAC have dose-dependent inhibitory activity against SARS-CoV-2 infection in Vero cells. PGG has a lower IC₅₀ (15.02 ± 0.75 μM) than PAC (25.90 ± 0.81 μM), suggesting that PGG has better inhibitory activity against SARS-CoV-2 than PAC. The PGG and PAC inhibit similar Mpro activities in a protease activity assay, with IC₅₀ values of 25–26 μM. The effects of PGG and PAC on the activity of the other essential SARS-CoV-2 viral protein, RdRp, were analyzed using a cell-based activity assay system. The activity of RdRp is inhibited by PGG and PAC, and PGG has a lower IC₅₀ (5.098 ± 1.089 μM) than PAC (21.022 ± 1.202 μM), which is consistent with their inhibitory capacity of SARS-CoV-2 infection. PGG and PAC also inhibit infection by SARS-CoV and MERS-CoV. These data indicate that PGG and PAC may be candidate broad-spectrum anticoronaviral therapeutic agents, simultaneously targeting the Mpro and RdRp proteins of SARS-CoV-2.

Potential Application of Tea Polyphenols to the Prevention of COVID-19 Infection: Based on the Gut-Lung Axis

Coronavirus disease 2019 (COVID-19) disrupts the intestinal micro-ecological balance, and patients often develop the intestinal disease. The gut is the largest immune organ in the human body; intestinal microbes can affect the immune function of the lungs through the gut-lung axis. It has been reported that tea polyphenols (TPs) have antiviral and prebiotic activity. In this review, we discussed TPs reduced lung-related diseases through gut-lung axis by inhibiting dysbiosis. In addition, we also highlighted the preventive and therapeutic effects of TPs on COVID-19 complications, further demonstrating the importance of research on TPs for the prevention and treatment of COVID-19 in humans. Based on this understanding, we recommend using TPs to regulate the gut microbiota to prevent or alleviate COVID-19 through the gut-lung axis.

Predicting global diet-disease relationships at the atomic level: a COVID-19 case study

Over the past few months, numerous studies harnessed in silico methods such as molecular docking to evaluate food compounds for inhibitory activity against coronavirus infection and replication. These studies capitalize on the efficiency of computational methods to quickly guide subsequent research and examine diet-disease relationships, and their sudden widespread utility may signal new opportunities for future antiviral and bioactive food research. Using Coronavirus Disease 2019 (COVID-19) research as a case study, we herein provide an overview of findings from studies using molecular docking to study food compounds as potential inhibitors of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), explore considerations for the critical interpretation of study findings, and discuss how these studies help shape larger conversations of diet and disease.

Progress on SARS-CoV-2 3CLpro Inhibitors: Inspiration from SARS-CoV 3CLpro Peptidomimetics and Small-Molecule Anti-Inflammatory Compounds

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) currently poses a threat to human health. 3C-like proteinase (3CLpro) plays an important role in the viral life cycle. Hence, it is considered an attractive antiviral target protein. Whole-genome sequencing showed that the sequence homology between SARS-CoV-2 3CLpro and SARS-CoV 3CLpro is 96.08%, with high similarity in the substrate-binding region. Thus, assessing peptidomimetic inhibitors of SARS-CoV 3CLpro could accelerate the development of peptidomimetic inhibitors for SARS-CoV-2 3CLpro. Accordingly, we herein discuss progress on SARS-CoV-2 3CLpro peptidomimetic inhibitors. Inflammation plays a major role in the pathophysiological process of COVID-19. Small-molecule compounds targeting 3CLpro with both antiviral and anti-inflammatory effects are also briefly discussed in this paper.

Inhibition of the main protease of SARS-CoV-2 (Mpro) by repurposing/designing drug-like substances and utilizing nature's toolbox of bioactive compounds

The emergence of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in a long pandemic, with numerous cases and victims worldwide and enormous consequences on social and economic life. Although vaccinations have proceeded and provide a valuable shield against the virus, the approved drugs are limited and it is crucial that further ways to combat infection are developed, that can also act against potential mutations. The main protease (Mpro) of the virus is an appealing target for the development of inhibitors, due to its importance in the viral life cycle and its high conservation among different coronaviruses. Several compounds have shown inhibitory potential against Mpro, both in silico and in vitro, with few of them also having entered clinical trials. These candidates include: known drugs that have been repurposed, molecules specifically designed based on the natural substrate of the protease or on structural moieties that have shown high binding affinity to the protease active site, as well as naturally derived compounds, either isolated or in plant extracts. The aim of this work is to collectively present the results of research regarding Mpro inhibitors to date, focusing on the function of the compounds founded by in silico simulations and further explored by in vitro and in vivo assays. Creating an extended portfolio of promising compounds that may block viral replication by inhibiting Mpro and by understanding involved structure-activity relationships, could provide a basis for the development of effective solutions against SARS-CoV-2 and future related outbreaks.

SARS-CoV-2 Survival in Common Non-Alcoholic and Alcoholic Beverages

SARS-CoV-2, the causative agent of COVID-19, is known to be transmitted by respiratory droplets and aerosols. Since the virus is shed at high concentrations in respiratory secretions and saliva, SARS-CoV-2 would also be expected to be transmitted through activities that involve the transfer of saliva from one individual to another, such as kissing or sharing beverages. To assess the survival of infectious SARS-CoV-2 in common beverages, we quantified infectious virus by plaque assays one hour after inoculation into 18 non-alcoholic and 16 alcoholic beverages, plus saliva, and also 7 days later for 5 of these beverages. SARS-CoV-2 remains infectious with minimal reductions in several common beverages, including milk and beer. However, cocoa, coffee, tea, fruit juices, and wine contain antiviral compounds that inactivate SARS-CoV-2. Although hard liquors containing 40% alcohol immediately inactivate SARS-CoV-2, mixing with non-alcoholic beverages reduces the antiviral effects. In summary, SARS-CoV-2 can be recovered from commonly consumed beverages in a beverage type and time-dependent manner. Although aerosol or droplet transmission remains the most likely mode of transmission, our findings combined with others suggest that beverages contaminated with SARS-CoV-2 during handling, serving, or through sharing of drinks should be considered as a potential vehicle for virus transmission.

Coronavirus enzyme inhibitors-experimentally proven natural compounds from plants

Coronavirus disease (COVID-19) can cause critical conditions that require efficient therapeutics. Several medicines are derived from plants, and researchers are seeking natural compounds to ameliorate the symptoms of COVID-19. Viral enzymes are popular targets of antiviral medicines; the genome of coronaviruses encodes several enzymes, including RNA-dependent RNA polymerase and viral proteases. Various screening systems have been developed to identify potential inhibitors. In this review, we describe the natural compounds that have been shown to exert inhibitory effects on coronavirus enzymes. Although computer-aided molecular structural studies have predicted several antiviral compound candidates, the current review focuses on experimentally proven natural compounds.

Discovery of Camellia sinensis catechins as SARS-CoV-2 3CL protease inhibitors through molecular docking, intra and extra cellular assays

BACKGROUND AND PURPOSE

Previous studies suggest that major Camellia sinensis (tea) catechins can inhibit 3-chymotrypsin-like cysteine protease (3CLpro), inspiring us to study 3CLpro inhibition of the recently discovered catechins from tea by our group.

METHODS

Autodock was used to dock 3CLpro and 16 tea catechins. Further, a 3CLpro activity detection system was used to test their intra and extra cellular 3CLpro inhibitory activity. Surface plasmon resonance (SPR) was used to analyze the dissociation constant (KD) between the catechins and 3CLpro.

RESULTS

Docking data suggested that 3CLpro interacted with the selected 16 catechins with low binding energy through the key amino acid residues Thr24, Thr26, Asn142, Gly143, His163, and Gln189. The selected catechins other than zijuanin D (3) and (-)-8-(5''R)-N-ethyl-2-pyrrolidinone-3-O-cinnamoylepicatechin (11) can inhibit 3CLpro intracellularly. The extracellular 3CLpro IC50 values of (-)-epicatechin 3-O-caffeoate (EC-C, 1), zijuanin C (2), etc-pyrrolidinone C and D (6), etc-pyrrolidinone A (9), (+)-gallocatechin gallate (GCG), and (-)-epicatechin gallate (ECG) are 1.58 ± 0.21, 41.2 ± 3.56, 0.90 ± 0.03, 46.71 ± 10.50, 3.38 ± 0.48, and 71.78 ± 8.36 µM, respectively. The KD values of 1, 6, and GCG are 4.29, 3.46, and 3.36 µM, respectively.

CONCLUSION

Together, EC-C (1), etc-pyrrolidinone C and D (6), and GCG are strong 3CLpro inhibitors. Our results suggest that structural modification of catechins could be conducted by esterificating the 3-OH as well as changing the configuration of C-3, C-3''' or C-5''' to discover strong SARS-CoV-2 inhibitors.

In silico evaluation of Vitis amurensis Rupr. polyphenol compounds for their inhibition potency against CoVID-19 main enzymes Mpro and RdRp

The rapid transmission of the pneumonia (COVID-19) emerged as an entire worldwide health concern and it was declared as pandemic by the World Health Organization (WHO) as a consequence of the increasing reported infections number. COVID-19 disease is caused by the novel SARS-CoV-2 virus, and unfortunatly no drugs are currently approved against this desease. Accordingly, it is of outmost importance to review the possible therapeutic effects of naturally-occuring compounds that showed approved antiviral activities. The molecular docking approach offers a rapid prediction of a possible inhibition of the main enzymes M^pro and RdRp that play crucial role in the SARS-CoV-2 replication and transcription. In the present work, we review the anti-viral activities of polyphenol compounds (phenolic acids, flavonoids and stilbene) derived from the traditional Chinese medicinal Vitis amurensis. Recent molecular docking studies reported the possible binding of these polyphenols on SARS-CoV-2 enzymes M^pro and RdRp active sites and showed interesting inhibitory effects. This antiviral activity was explained by the structure-activity relationships of the studied compounds. Also, pharmacokinetic analysis of the studied molecules is simulated in the present work. Among the studied polyphenol compounds, only five, namely caffeic acid, ferulic acid, quercetin, naringenin and catechin have drug-likeness characteristics. These five polyphenols derived from Vitis amurensis are promising drug candidates for the COVID-19 treatment.

Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

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.

Epigallocatechin Gallate (EGCG), a Green Tea Polyphenol, Reduces Coronavirus Replication in a Mouse Model

The COVID-19 pandemic has resulted in a huge number of deaths from 2020 to 2021; however, effective antiviral drugs against SARS-CoV-2 are currently under development. Recent studies have demonstrated that green tea polyphenols, particularly EGCG, inhibit coronavirus enzymes as well as coronavirus replication in vitro. Herein, we examined the inhibitory effect of green tea polyphenols on coronavirus replication in a mouse model. We used epigallocatechin gallate (EGCG) and green tea polyphenols containing more than 60% catechin (GTP60) and human coronavirus OC43 (HCoV-OC43) as a surrogate for SARS-CoV-2. Scanning electron microscopy analysis results showed that HCoV-OC43 infection resulted in virion particle production in infected cells. EGCG and GTP60 treatment reduced coronavirus protein and virus production in the cells. Finally, EGCG- and GTP60-fed mice exhibited reduced levels of coronavirus RNA in mouse lungs. These results demonstrate that green tea polyphenol treatment is effective in decreasing the level of coronavirus in vivo.

Characterization of the Trans-Epithelial Transport of Green Tea (C. sinensis) Catechin Extracts with In Vitro Inhibitory Effect against the SARS-CoV-2 Papain-like Protease Activity

This work describes an untargeted analytical approach for the screening, identification, and characterization of the trans-epithelial transport of green tea (Camellia sinensis) catechin extracts with in vitro inhibitory effect against the SARS-CoV-2 papain-like protease (PLpro) activity. After specific catechin extraction, a chromatographic separation obtained six fractions were carried out. The fractions were assessed in vitro against the PLpro target. Fraction 5 showed the highest inhibitory activity against the SARS-CoV-2 PLpro (IC₅₀ of 0.125 μg mL^-1). The untargeted characterization revealed that (-)-epicatechin-3-gallate (ECG) was the most abundant compound in the fraction and the primary molecule absorbed by differentiated Caco-2 cells. Results indicated that fraction 5 was approximately 10 times more active than ECG (IC₅₀ value equal to 11.62 ± 0.47 μg mL^-1) to inhibit the PLpro target. Overall, our findings highlight the synergistic effects of the various components of the crude extract compared to isolated ECG.

Enhancing Flavan-3-ol Biosynthesis in Saccharomyces cerevisiae

Flavan-3-ols are a group of flavonoids that exert beneficial effects. This study aimed to enhance key metabolic processes related to flavan-3-ols biosynthesis. The engineered Saccharomyces cerevisiae strain E32 that produces naringenin from glucose was further engineered for de novo production of two basic flavan-3-ols, afzelechin (AFZ) and catechin (CAT). Through introduction of flavonoid 3-hydroxylase, flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase (DFR), and leucoanthocyanidin reductase (LAR), de novo production of AFZ and CAT can be achieved. The combination of FaDFR from Fragaria × ananassa and VvLAR from Vitis vinifera was optimal. (GGGGS)₂ and (EAAAK)₂ linkers between DFR and LAR proved optimal for the production of AFZ and CAT, respectively. Optimization of promoters and the enhanced supply of NADPH further increased the production. By combining the best engineering strategies, the optimum strains produced 500.5 mg/L AFZ and 321.3 mg/L CAT, respectively, after fermentation for 90 h in a 5 L bioreactor. The strategies presented could be applied for a more efficient production of flavan-3-ols by various microorganisms.

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.

Tea crude extracts effectively inactivate severe acute respiratory syndrome coronavirus 2

It is well known that black and green tea extracts, particularly polyphenols, have antimicrobial activity against various pathogenic microbes including viruses. However, there is limited data on the antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), which emerged rapidly in China in late 2019 and which has been responsible for coronavirus disease 2019 (COVID‐19) pandemic globally. In this study, 20 compounds and three extracts were obtained from black and green tea and found that three tea extracts showed significant antiviral activity against SARS‐CoV‐2, whereby the viral titre decreased about 5 logs TCID₅₀ per ml by 1·375 mg ml⁻¹ black tea extract and two‐fold diluted tea bag infusion obtained from black tea when incubated at 25°C for 10 s. However, when concentrations of black and green tea extracts were equally adjusted to 344 µg ml⁻¹, green tea extracts showed more antiviral activity against SARS‐CoV‐2. This simple and highly respected beverage may be a cheap and widely acceptable means to reduce SARS‐CoV‐2 viral burden in the mouth and upper gastrointestinal and respiratory tracts in developed as well as developing countries.

Targeting autophagy with natural products to prevent SARS-CoV-2 infection

Autophagy is a catabolic process that maintains internal homeostasis and energy balance through the lysosomal degradation of redundant or damaged cellular components. During virus infection, autophagy is triggered both in parenchymal and in immune cells with different finalistic objectives: in parenchymal cells, the goal is to destroy the virion particle while in macrophages and dendritic cells the goal is to expose virion-derived fragments for priming the lymphocytes and initiate the immune response. However, some viruses have developed a strategy to subvert the autophagy machinery to escape the destructive destiny and instead exploit it for virion assembly and exocytosis. Coronaviruses (like SARS-CoV-2) possess such ability. The autophagy process requires a set of proteins that constitute the core machinery and is controlled by several signaling pathways. Here, we report on natural products capable of interfering with SARS-CoV-2 cellular infection and replication through their action on autophagy. The present study provides support to the use of such natural products as adjuvant therapeutics for the management of COVID-19 pandemic to prevent the virus infection and replication, and so mitigating the progression of the disease.

Recent insights on tea metabolites, their biosynthesis and chemo-preventing effects: A review

Tea manufactured from the cultivated shoots of Camellia sinensis (L.) O. Kuntze is the most commonly consumed nonalcoholic drink around the world. Tea is an agro-based, environmentally sustainable, labor-intensive, job-generating, and export-oriented industry in many countries. Tea includes phenolic compounds, flavonoids, alkaloids, vitamins, enzymes, crude fibers, protein, lipids, and carbohydrates, among other biochemical constituents. This review described the nature of tea metabolites, their biosynthesis and accumulation with response to various factors. The therapeutic application of various metabolites of tea against microbial diseases, cancer, neurological, and other metabolic disorders was also discussed in detail. The seasonal variation, cultivation practices and genetic variability influence tea metabolite synthesis. Tea biochemical constituents, especially polyphenols and its integral part catechin metabolites, are broadly focused on potential applicability for their action against various diseases. In addition to this, tea also contains bioactive flavonoids that possess health-beneficial effects. The catechin fractions, epigallocatechin 3-gallate and epicatechin 3-gallate, are the main components of tea that has strong antioxidant and medicinal properties. The synergistic function of natural tea metabolites with synthetic drugs provides effective protection against various diseases. Furthermore, the application of nanotechnologies enhanced bioavailability, enhancing the therapeutic potential of natural metabolites against numerous diseases and pathogens.

Catechins: Therapeutic Perspectives in COVID-19-Associated Acute Kidney Injury

Data obtained from several intensive care units around the world have provided substantial evidence of the strong association between impairment of the renal function and in-hospital deaths of critically ill COVID-19 patients, especially those with comorbidities and requiring renal replacement therapy (RRT). Acute kidney injury (AKI) is a common renal disorder of various etiologies characterized by a sudden and sustained decrease of renal function. Studies have shown that 5-46% of COVID-19 patients develop AKI during hospital stay, and the mortality of those patients may reach up to 100% depending on various factors, such as organ failures and RRT requirement. Catechins are natural products that have multiple pharmacological activities, including anti-coronavirus and reno-protective activities against kidney injury induced by nephrotoxic agents, obstructive nephropathies and AKI accompanying metabolic and cardiovascular disorders. Therefore, in this review, we discuss the anti-SARS-CoV-2 and reno-protective effects of catechins from a mechanistic perspective. We believe that catechins may serve as promising therapeutics in COVID-19-associated AKI due to their well-recognized anti-SARS-CoV-2, and antioxidant and anti-inflammatory properties that mediate their reno-protective activities.