Development of Ultrapure and Potent Tannic Acids as a Pan-coronal Antiviral Therapeutic

Galloylated polyphenols represent a new class of antithrombotic agents with broad activity against thiol isomerases

BACKGROUND

Both protein disulfide isomerase (PDI) and SARS-CoV-2 main protease (Mpro) are reliant on active-site cysteines stabilized by adjacent amino acids. We reasoned that redox-active compounds might interfere with both enzymes by acting in the vicinity of these reactive sites thus interfering with viral replication and thrombus formation. Our previous screen of 1019 flavonoids identified several compounds that inhibit SARS-CoV-2 Mpro.

OBJECTIVES

Our goal was to identify phytochemical inhibitors of SARS-CoV-2 Mpro that block thiol isomerases and are antithrombotic.

METHODS

PDI, ERp57, ERp5, ERp46, isolated domains of PDI, and PDI mutants were used to evaluate the effects of galloylated polyphenols and their analogs on thiol isomerase reductase activity. Laser-injury and ferric chloride models of thrombus formation and a tail snip assay were used to assess the effects on thrombosis and hemostasis.

RESULTS

Pinocembrin 7-O-(3''-galloyl-4'',6''-(S)-hexahydroxydiphenoyl)-β-D-glucose (PGHG) inhibited both PDI and SARS-CoV-2 Mpro. Evaluation of isolated PDI fragments and active-site cysteine mutants showed that PGHG acts at the catalytic domains. Structure-function studies showed that PGHG interacts with histidines within the Cys53-Gly54-His55-Cys56 motifs of PDI. PGHG was equally active against other thiol isomerases, including ERp57, ERp5, ERp72, and ERp46. Screening numerous galloylated polyphenols demonstrated a class effect on thiol isomerase inhibition. Structure-activity relationships indicated that the galloyl moieties within large galloylated polyphenols were important for their inhibitory activity. PGHG and punicalagin were antithrombotic in murine models of thrombus formation.

CONCLUSIONS

Galloylated polyphenols represent a large class of antithrombotic compounds with broad activity against thiol isomerases. Many of these compounds also inhibit SARS-CoV-2 Mpro and viral replication.

Progress in Research on Inhibitors Targeting SARS-CoV-2 Main Protease (Mpro)

Since 2019, the novel coronavirus (SARS-CoV-2) has caused significant morbidity and millions of deaths worldwide. The Coronavirus Disease 2019 (COVID-19), caused by SARS-CoV-2 and its variants, has further highlighted the urgent need for the development of effective therapeutic agents. Currently, the highly conserved and broad-spectrum nature of main proteases (Mpro) renders them of great importance in the field of inhibitor study. In this study, we categorize inhibitors targeting Mpro into three major groups: mimetic, nonmimetic, and natural inhibitors. We then present the research progress of these inhibitors in detail, including their mechanism of action, antiviral activity, pharmacokinetic properties, animal experiments, and clinical studies. This review aims to provide valuable insights and potential avenues for the development of more effective antiviral drugs against SARS-CoV-2.

Myocardial Oedema as a Consequence of Viral Infection and Persistence-A Narrative Review with Focus on COVID-19 and Post COVID Sequelae

Microvascular integrity is a critical factor in myocardial fluid homeostasis. The subtle equilibrium between capillary filtration and lymphatic fluid removal is disturbed during pathological processes leading to inflammation, but also in hypoxia or due to alterations in vascular perfusion and coagulability. The degradation of the glycocalyx as the main component of the endothelial filtration barrier as well as pericyte disintegration results in the accumulation of interstitial and intracellular water. Moreover, lymphatic dysfunction evokes an increase in metabolic waste products, cytokines and inflammatory cells in the interstitial space contributing to myocardial oedema formation. This leads to myocardial stiffness and impaired contractility, eventually resulting in cardiomyocyte apoptosis, myocardial remodelling and fibrosis. The following article reviews pathophysiological inflammatory processes leading to myocardial oedema including myocarditis, ischaemia-reperfusion injury and viral infections with a special focus on the pathomechanisms evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In addition, clinical implications including potential long-term effects due to viral persistence (long COVID), as well as treatment options, are discussed.

Bench-to-bedside: Innovation of small molecule anti-SARS-CoV-2 drugs in China

The ongoing COVID-19 pandemic has resulted in millions of deaths globally, highlighting the need to develop potent prophylactic and therapeutic strategies against SARS-CoV-2. Small molecule inhibitors (remdesivir, Paxlovid, and molnupiravir) are essential complements to vaccines and play important roles in clinical treatment of SARS-CoV-2. Many advances have been made in development of anti-SARS-CoV-2 inhibitors in China, but progress in discovery and characterization of pharmacological activity, antiviral mechanisms, and clinical efficacy are limited. We review development of small molecule anti-SARS-CoV-2 drugs (azvudine [approved by the NMPA of China on July 25, 2022], VV116 [approved by the NMPA of China on January 29, 2023], FB2001, WPV01, pentarlandir, and cepharanthine) in China and summarize their pharmacological activity, potential mechanisms of action, clinical trials and use, and important milestones in their discovery. The role of structural biology in drug development is also reviewed. Future studies should focus on development of diverse second-generation inhibitors with excellent oral bioavailability, superior plasma half-life, increased antiviral activity against SARS-CoV-2 and its variants, high target specificity, minimal side effects, reduced drug-drug interactions, and improved lung histopathology.

Inspired by nature: Fiber networks functionalized with tannic acid and condensed tannin-rich extracts of Norway spruce bark show antimicrobial efficacy

This study demonstrated the antibacterial and antiviral potential of condensed tannins and tannic acid when incorporated into fiber networks tested for functional material purposes. Condensed tannins were extracted from industrial bark of Norway spruce by using pressurized hot water extraction (PHWE), followed by purification of extracts by using XADHP7 treatment to obtain sugar-free extract. The chemical composition of the extracts was analyzed by using HPLC, GC‒MS and UHPLC after thiolytic degradation. The test matrices, i.e., lignocellulosic handsheets, were produced and impregnated with tannin-rich extracts, and tannic acid was used as a commercial reference. The antibacterial and antiviral efficacy of the handsheets were analyzed by using bioluminescent bacterial strains (Staphylococcus aureus RN4220+pAT19 and Escherichia coli K12+pCGLS11) and Enterovirus coxsackievirus B3. Potential bonding of the tannin-rich extract and tannic acid within the fiber matrices was studied by using FTIR-ATR spectroscopy. The deposition characteristics (distribution and accumulation patterns) of tannin compounds and extracts within fiber networks were measured and visualized by direct chemical mapping using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and digital microscopy. Our results demonstrated for the first time, how tannin-rich extracts obtained from spruce bark side streams with green chemistry possess antiviral and antibacterial properties when immobilized into fiber matrices to create substitutes for plastic hygienic products, personal protection materials such as surgical face masks, or food packaging materials to prolong the shelf life of foodstuffs and prevent the spread of infections. However, more research is needed to further develop this proof-of-concept to ensure stable chemical bonding in product prototypes with specific chemistry.