Corilagin and 1,3,6-Tri-O-galloy-ß-D-glucose: potential inhibitors of SARS-CoV-2 variants.

The COVID-19 disease caused by the virus SARS-CoV-2, first detected in December 2019, is still emerging through virus mutations. Although almost under control in some countries due to effective vaccines that are mitigating the worldwide pandemic, the urgency to develop additional vaccines and therapeutic treatments is imperative. In this work, the natural polyphenols corilagin and 1,3,6-tri-O-galloy-ß-d-glucose (TGG) are investigated to determine the structural basis of inhibitor interactions as potential candidates to inhibit SARS-CoV-2 viral entry into target cells. First, the therapeutic potential of the ligands are assessed on the ACE2/wild-type RBD. We first use molecular docking followed by molecular dynamics, to take into account the conformational flexibility that plays a significant role in ligand binding and that cannot be captured using only docking, and then analyze more precisely the affinity of these ligands using MMPBSA binding free energy. We show that both ligands bind to the ACE2/wild-type RBD interface with good affinities which might prevent the ACE2/RBD association. Second, we confirm the potency of these ligands to block the ACE2/RBD association using a combination of surface plasmon resonance and biochemical inhibition assays. These experiments confirm that TGG and, to a lesser extent, corilagin, inhibit the binding of RBD to ACE2. Both experiments and simulations show that the ligands interact preferentially with RBD, while weak binding is observed with ACE2, hence, avoiding potential physiological side-effects induced by the inhibition of ACE2. In addition to the wild-type RBD, we also study numerically three RBD mutations (E484K, N501Y and E484K/N501Y) found in the main SARS-CoV-2 variants of concerns. We find that corilagin could be as effective for RBD/E484K but less effective for the RBD/N501Y and RBD/E484K-N501Y mutants, while TGG strongly binds at relevant locations to all three mutants, demonstrating the significant interest of these molecules as potential inhibitors for variants of SARS-CoV-2.

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.

Leonurine Ameliorates Oxidative Stress and Insufficient Angiogenesis by Regulating the PI3K/Akt-eNOS Signaling Pathway in H2O2-Induced HUVECs.

Thrombus is considered to be the pathological source of morbidity and mortality of cardiovascular disease and thrombotic complications, while oxidative stress is regarded as an important factor in vascular endothelial injury and thrombus formation. Therefore, antioxidative stress and maintaining the normal function of vascular endothelial cells are greatly significant in regulating vascular tension and maintaining a nonthrombotic environment. Leonurine (LEO) is a unique alkaloid isolated from Leonurus japonicus Houtt (a traditional Chinese medicine (TCM)), which has shown a good effect on promoting blood circulation and removing blood stasis. In this study, we explored the protective effect and action mechanism of LEO on human umbilical vein endothelial cells (HUVECs) after damage by hydrogen peroxide (H2O2). The protective effects of LEO on H2O2-induced HUVECs were determined by measuring the cell viability, cell migration, tube formation, and oxidative biomarkers. The underlying mechanism of antioxidation of LEO was investigated by RT-qPCR and western blotting. Our results showed that LEO treatment promoted cell viability; remarkably downregulated the intracellular generation of reactive oxygen species (ROS), malondialdehyde (MDA) production, and lactate dehydrogenase (LDH); and upregulated the nitric oxide (NO) and superoxide dismutase (SOD) activity in H2O2-induced HUVECs. At the same time, LEO treatment significantly promoted the phosphorylation level of angiogenic protein PI3K, Akt, and eNOS and the expression level of survival factor Bcl2 and decreased the expression level of death factor Bax and caspase3. In conclusion, our findings suggested that LEO can ameliorate the oxidative stress damage and insufficient angiogenesis of HUVECs induced by H2O2 through activating the PI3K/Akt-eNOS signaling pathway.

GB-2 blocking the interaction between ACE2 and wild type and mutation of spike protein of SARS-CoV-2.

Since the start of the outbreak of coronavirus disease 2019 in Wuhan, China, there have been more than 150 million confirmed cases of the disease reported to the World Health Organization. The beta variant (B.1.351 lineage), the mutation lineages of SARS-CoV-2, had increase transmissibility and resistance to neutralizing antibodies due to multiple mutations in the spike protein. N501Y, K417N and E484K, in the receptor binding domain (RBD) region may induce a conformational change of the spike protein and subsequently increase the infectivity of the beta variant. The L452R mutation in the epsilon variant (the B.1.427/B.1.429 variants) also reduced neutralizing activity of monoclonal antibodies. In this study, we discovered that 300 µg/mL GB-2, from Tian Shang Sheng Mu of Chiayi Puzi Peitian Temple, can inhibit the binding between ACE2 and wild-type (Wuhan type) RBD spike protein. GB-2 can inhibit the binding between ACE2 and RBD with K417N-E484K-N501Y mutation in a dose-dependent manner. GB-2 inhibited the binding between ACE2 and the RBD with a single mutation (K417N or N501Y or L452R) except the E484K mutation. In the compositions of GB-2, glycyrrhiza uralensis Fisch. ex DC., theaflavin and (+)-catechin cannot inhibit the binding between ACE2 and wild-type RBD spike protein. Theaflavin 3-gallate can inhibit the binding between ACE2 and wild-type RBD spike protein. Our results suggest that GB-2 could be a potential candidate for the prophylaxis of some SARS-CoV-2 variants infection in the further clinical study because of its inhibition of binding between ACE2 and RBD with K417N-E484K-N501Y mutations or L452R mutation.

Significant Inactivation of SARS-CoV-2 In Vitro by a Green Tea Catechin, a Catechin-Derivative, and Black Tea Galloylated Theaflavins.

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

A molecular docking study of EGCG and theaflavin digallate with the druggable targets of SARS-CoV-2.

BACKGROUND: COVID-19 is an infectious disease caused by a novel positive-sense single-stranded RNA coronavirus called as SARS-CoV-2. This viral disease is known to infect the respiratory system, eventually leading to pneumonia. Crystallographic studies of the viral structure reveal its mechanism of infection as well as active binding sites and the druggable targets as scope for treatment of COVID-19. HYPOTHESIS: The role of tea polyphenols in prophylaxis and treatment of COVID-19 was established in this study. STUDY DESIGN: Molecular docking interactions of tea polyphenols with some of the possible binding sites of SARS-CoV-2 were performed. MATERIALS AND METHODS: From various studies on the SARS-CoV-2 reported in the literature, we chose possible drug targets (Chymotrypsin-like protease, RNA dependant RNA polymerase, Papain like protease, Spike RBD and ACE2 receptor with spike RBD) which are vital proteins. These receptors were docked against two tea polyphenols, Epigallocatechin gallate (EGCG) from green tea and Theaflavin digallate (TF3) from black tea. These polyphenols have been previously reviewed for their antiviral activities, especially against single-stranded RNA viruses. Two antiviral drugs, Remdesivir and Favipiravir were studied for comparative docking results. RESULTS: A comparative study of docking scores and the type of interactions of EGCG, TF3 with the possible targets of COVID-19 showed that the tea polyphenols had good docking scores with significant in-silico activity. CONCLUSION: These results can provide a lead in exploring both the tea polyphenols in prophylaxis as well as treatment of COVID-19.

Epigallocatechin gallate and theaflavin gallate interaction in SARS-CoV-2 spike-protein central channel with reference to the hydroxychloroquine interaction: Bioinformatics and molecular docking study.

SARS-CoV-2 or COVID-19 pandemic global outbreak created the most unstable situation of human health-economy. In the past two decades different parts of the word experienced smaller or bigger outbreak related to human coronaviruses. The spike glycoproteins of the COVID-19 (similar to SARS-CoV) attach to the angiotensin-converting enzyme (ACE2) and transit over a stabilized open state for the viral internalization to the host cells and propagate with great efficacy. Higher rate of mutability makes this virus unpredictable/less sensitive to the protein/nucleic acid based drugs. In this emergent situation, drug-induced destabilization of spike binding to RBD could be a good strategy. In the current study we demonstrated by bioinformatics (CASTp: computed atlas of surface topography of protein, PyMol: molecular visualization) and molecular docking (PatchDock and Autodock) experiments that tea flavonoids catechin products mainly epigallocatechin gallate or other like theaflavin gallate demonstrated higher atomic contact energy (ACE) value, binding energy, Ki value, ligand efficiency, surface area and more amino acid interactions than hydroxychloroquine (HCQ) during binding in the central channel of the spike protein. Moreover, out of three distinct binding sites (I, II and III) of spike core when HCQ binds only with site III (farthest from the nCoV-RBD of ACE2 contact), epigallocatechin gallate and theaflavin gallate bind all three sites. As sites I and II are in closer contact with open state location and viral-host contact area, these drugs might have significant effects. Taking into account the toxicity/side effects by chloroquine/HCQ, present drugs may be important. Our laboratory is working on tea flavonoids and other phytochemicals in the protection from toxicity, DNA/mitochondrial damage, inflammation and so on. The present data might be helpful for further analysis of flavonoids in this emergent pandemic situation.