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We investigate the inhibition mechanism between pomotrelvir and the SARS‐CoV‐2 main protease using molecular mechanics and quantum mechanics/molecular mechanics simulations. Alchemical transformations where each Pi group of pomotrelvir was transformed into its counterpart in nirmatrelvir were performed to unravel the individual contribution of each group to the binding and reaction processes. We have shown that while a γ‐lactam ring is preferred at position P1, a δ‐lactam ring is a good alternative for the design of inhibitors for variants presenting mutations at position 166. For the P2 position, tertiary amines are preferred with respect to secondary amines. Flexible side chains at the P2 position can disrupt the preorganization of the active site, favouring the exploration of non‐reactive conformations. The substitution of the P2 group of pomotrelvir by that of nirmatrelvir resulted in a compound, named as C2, that presents a better binding free energy and a higher population of reactive conformations in the Michaelis complex. Analysis of the chemical reaction to form the covalent complex has shown a similar reaction mechanism and activation free energies for pomotrelvir, nirmatrelvir and C2. We hope that these findings could be useful to design better inhibitors to fight present and future variants of the SARS‐CoV‐2 virus. [ABSTRACT FROM AUTHOR]

In December 2019, the first COVID-19 cases were in Wuhan, China. This case is a global concern and a threat to public health. Based on previous research using molecular docking methods, it was found that flavonoids exhibit strong inhibitory activity in SARS-CoV-2 main proteases. The study aims to determine the flavonoid compound Syzygium cumini (L.) Skeels can interact with the SARS-CoV-2 main protease receptor and can be used as a candidate for COVID-19 therapy with virtual screening. Myricetin 4”-O-acetyl-2-O-gallate has the lowest Gibbs free energy (ΔG) of -9.82 kcal/mol. The molecular dynamics of the best compound, Myrcetin 4-O-acetyl-2-O-gallate, RMSD, and RSMF values are quite stable. As a result of pharmacokinetic prediction and toxicity, the best compounds have a relatively good pharmacokinetic profile and are non-toxic. Thus, it can be concluded that the compound Myricetin 4”-O-acetyl-2-o-gallate in the Syzygium cumini (L.) Skeels is predicted to interact with the SARS-CoV-2 main protease receptor (7C6S) as a potential drug candidate for COVID-19 therapy.

In December 2019, the first COVID-19 cases were in Wuhan, China. This case is a global concern and a threat to public health. Based on previous research using molecular docking methods, it was found that flavonoids exhibit strong inhibitory activity in SARS-CoV-2 main proteases. The study aims to determine the flavonoid compound Syzygium cumini (L.) Skeels can interact with the SARS-CoV- 2 main protease receptor and can be used as a candidate for COVID-19 therapy with virtual screening. Myricetin 4”-O-acetyl-2-O-gallate has the lowest Gibbs free energy (ΔG) of -9.82 kcal/mol. The molecular dynamics of the best compound, Myrcetin 4-O-acetyl-2-O-gallate, RMSD, and RSMF values are quite stable. As a result of pharmacokinetic prediction and toxicity, the best compounds have a relatively good pharmacokinetic profile and are non-toxic. Thus, it can be concluded that the compound Myricetin 4”-O-acetyl-2-o-gallate in the Syzygium cumini (L.) Skeels is predicted to interact with the SARS-CoV-2 main protease receptor (7C6S) as a potential drug candidate for COVID-19 therapy. [ABSTRACT FROM AUTHOR]

The development of specific antiviral therapies targeting SARS-CoV-2 remains fundamental because of the continued high incidence of COVID-19 and limited accessibility to antivirals in some countries. In this context, dark chemical matter (DCM), a set of drug-like compounds with outstanding selectivity profiles that have never shown bioactivity despite being extensively assayed, appears to be an excellent starting point for drug development. Accordingly, in this study, we performed a high-throughput screening to identify inhibitors of the SARS-CoV-2 main protease (Mpro) using DCM compounds as ligands. Multiple receptors and two different docking scoring functions were employed to identify the best molecular docking poses. The selected structures were subjected to extensive conventional and Gaussian accelerated molecular dynamics. From the results, four compounds with the best molecular behavior and binding energy were selected for experimental testing, one of which presented inhibitory activity with a Ki value of 48 ± 5 μM. Through virtual screening, we identified a significant starting point for drug development, shedding new light on DCM compounds. [ABSTRACT FROM AUTHOR]

This review article aims to significantly advance the scientific community's efforts to develop effective nucleoside‐based drugs for treating severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and other emerging infectious diseases. This study concentrates on the main viral protease (Mpro) and explores nucleoside‐based compounds as potential therapeutic agents. This investigation investigated the impact of acylation‐induced modifications on the nucleoside hydroxyl group and subsequent properties. Nucleoside analogs, which are recognized for their diverse biochemical properties, were synthesized and rigorously screened to evaluate their antimicrobial efficacy. In the domain of pharmaceutical research, computational pharmacokinetics has emerged as a critical tool, especially in the pursuit of nucleoside analogs as potential therapeutics. In silico methods aid in predicting pharmacokinetic traits, interactions with crucial enzymes, and the stability of these analogs in biological environments, thereby streamlining drug design and reducing experimental costs. Concurrently, computational studies revealed the intricate interactions between the analogs and the active site of the main protease. The amalgamation of experimental screening and computational insights underscores the emergence of potent nucleoside candidates with inhibitory activity against SARS‐CoV‐2 Mpro. Additionally, this review integrates computational studies that provide valuable insights into the interactions between nucleoside analogs and the main protease of SARS‐CoV‐2. [ABSTRACT FROM AUTHOR]

Objective: Recent evidence reported that some dietary compounds like quercetin and apigenin as the most well-known flavonoids with anti-inflammatory effects may inhibit SARS-CoV-2 main protease. The hypothesis of the promising effects and possible mechanisms of action of quercetin against COVID-19 were assessed in this article.Materials and Methods: Related papers on the inhibitory effects of quercetin against COVID-19 were collected using the following search strategy: “corona or coronavirus or COVID or COVID-19 or viral or virus” AND “nutrient or flavonoid or Quercetin”.Results: The findings indicated that quercetin can be considered an effective agent against COVID-19 because of its SARS-CoV-2 main protease and RNA-dependent RNA polymerase inhibitory effects. In addition, quercetin may attenuate angiotensin-converting enzyme-2 (ACE-2) receptors leading to a reduction of SARS-CoV-2 ability to enter host cells. Moreover, the antiviral, anti-inflammatory, and immunomodulatory activities of quercetin have been frequently reported.Conclusion: Quercetin may be an effective agent for managing the complications of COVID-19. Further longitudinal human studies are warranted.

Protein‐templated fragment ligation was established as a method for the rapid identification of high affinity ligands, and multicomponent reactions (MCR) such as the Ugi four‐component reaction (Ugi 4CR) have been efficient in the synthesis of drug candidates. Thus, the combination of both strategies should provide a powerful approach to drug discovery. Here, we investigate protein‐templated Ugi 4CR quantitatively using a fluorescence‐based enzyme assay, HPLC‐QTOF mass spectrometry (MS), and native protein MS with SARS‐CoV‐2 main protease as template. Ugi reactions were analyzed in aqueous buffer at varying pH and fragment concentration. Potent inhibitors of the protease were formed in presence of the protein via Ugi 4CR together with Ugi three‐component reaction (Ugi 3CR) products. Binding of inhibitors to the protease was confirmed by native MS and resulted in the dimerization of the protein target. Formation of Ugi products was, however, more efficient in the non‐templated reaction, apparently due to interactions of the protein with the isocyanide and imine fragments. Consequently, in‐situ ligation screening of Ugi 4CR products was identified as a superior approach to the discovery of SARS‐CoV‐2 protease inhibitors. [ABSTRACT FROM AUTHOR]

Objective: Recent evidence reported that some dietary compounds like quercetin and apigenin as the most well-known flavonoids with anti-inflammatory effects may inhibit SARS-CoV-2 main protease. The hypothesis of the promising effects and possible mechanisms of action of quercetin against COVID-19 were assessed in this article. Materials and Methods: Related papers on the inhibitory effects of quercetin against COVID-19 were collected using the following search strategy: "corona or coronavirus or COVID or COVID-19 or viral or virus" AND "nutrient or flavonoid or Quercetin". Results: The findings indicated that quercetin can be considered an effective agent against COVID-19 because of its SARS-CoV-2 main protease and RNA-dependent RNA polymerase inhibitory effects. In addition, quercetin may attenuate angiotensinconverting enzyme-2 (ACE-2) receptors leading to a reduction of SARS-CoV-2 ability to enter host cells. Moreover, the antiviral, anti-inflammatory, and immunomodulatory activities of quercetin have been frequently reported. Conclusion: Quercetin may be an effective agent for managing the complications of COVID-19. Further longitudinal human studies are warranted. [ABSTRACT FROM AUTHOR]

Prevention from disease is presently the cornerstone of the fight against COVID-19. With the rapid emergence of novel SARS-CoV-2 variants, there is an urgent need for novel or repurposed agents to strengthen and fortify the immune system. Existing vaccines induce several systemic and local side-effects that can lead to severe consequences. Moreover, elevated cytokines in COVID-19 patients with cancer as co-morbidity represent a significant bottleneck in disease prognosis and therapy. Withania somnifera (WS) and its phytoconstituent(s) have immense untapped immunomodulatory and therapeutic potential and the anticancer potential of WS is well documented. To this effect, WS methanolic extract (WSME) was characterized using HPLC. Withanolides were identified as the major phytoconstituents. In vitro cytotoxicity of WSME was determined against human breast MDA-MB-231 and normal Vero cells using MTT assay. WSME displayed potent cytotoxicity against MDA-MB-231 cells (IC50: 66 µg/mL) and no effect on Vero cells in the above range. MD simulations of Withanolide A with SARS-CoV-2 main protease and spike receptor-binding domain as well as Withanolide B with SARS-CoV spike glycoprotein and SARS-CoV-2 papain-like protease were performed using Schrödinger. Stability of complexes followed the order 6M0J-Withanolide A > 6W9C-Withnaolide B > 5WRG-Withanolide B > 6LU7-Withanolide A. Maximum stable interaction(s) were observed between Withanolides A and B with SARS-CoV-2 and SARS-CoV spike glycoproteins, respectively. Withanolides A and B also displayed potent binding to pro-inflammatory markers viz. serum ferritin and IL-6. Thus, WS phytoconstituents have the potential to be tested further in vitro and in vivo as novel antiviral agents against COVID-19 patients having cancer as a co-morbidity. [ABSTRACT FROM AUTHOR]

Predicting the potency of inhibitors is key to in silico screening of promising synthetic or natural compounds. Here we describe a predictive workflow that provides calculated inhibitory values, which concord well with empirical data. Calculations of the free interaction energy ΔG with the YASARA plugin FoldX were used to derive inhibition constants Ki from PDB coordinates of protease–inhibitor complexes. At the same time, corresponding KD values were obtained from the PRODIGY server. These results correlated well with the experimental values, particularly for serine proteases. In addition, analyses were performed for inhibitory complexes of cysteine and aspartic proteases, as well as of metalloproteases, whereby the PRODIGY data appeared to be more consistent. Based on our analyses, we calculated theoretical Ki values for trypsin with sunflower trypsin inhibitor (SFTI-1) variants, which yielded the more rigid Pro14 variant, with probably higher potency than the wild-type inhibitor. Moreover, a hirudin variant with an Arg1 and Trp3 is a promising basis for novel thrombin inhibitors with high potency. Further examples from antibody interaction and a cancer-related effector-receptor system demonstrate that our approach is applicable to protein interaction studies beyond the protease field. [ABSTRACT FROM AUTHOR]

Imidazole-based compounds form a prominent class of heterocyclic compounds, displaying diverse applications, especially with regards to its biological and pharmacological activities. Molecular docking, simulations, and drug-likeness prediction were performed on 45 imidazole-based alkaloids from two species of marine sponges (Leucetta and Clathrina). The study seeks to identify possible inhibitors of the SARS-CoV-2 Main Protease in an effort to battle the prevailing pandemic which has been caused by the widespread infections of the SAR-CoV-2 virus in its varied mutated forms. Computational analysis with MOE 2015.10 program reveals that, among the imidazole-based alkaloids, Naamidines have a high affinity for the target protein (PDB ID:6W63), even interacting with the catalytic dyad, as compared to its non-covalent inhibitor X77. Among all the top-scoring ligands, Naamidine H produced the highest binding score of −8.87078 kcal/mol. MD simulation studies with NAMD confirms the stability of the interactions of Naamidines with the target protein. MM-GBSA calculations were performed on the top binding ligands which further confirms the binding affinity of the top-scoring ligands. Computational and pharmacological investigations in this study proposes Naamidines, as effective inhibitors of Mpro. Naamidine I, Naamidine E, and Pyronaamidine could be potential anti-viral candidates against SAR-CoV-2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Application of QSAR with Machine Learning techniques on the Ebselen compounds as training data related to their SAR-CoV-2 protein target. • Identify the Ebselen binding conformation using the ligand-binding pathway sampling method based on parallel cascade selection molecular dynamics (LB-PaCS-MD). • Providing new designed compounds which meet both ligand-based drug design and structure-based drug design approaches. The global outbreak of the COVID-19 pandemic caused by the SARS-CoV-2 virus had led to profound respiratory health implications. This study focused on designing organoselenium-based inhibitors targeting the SARS-CoV-2 main protease (Mpro). The ligand-binding pathway sampling method based on parallel cascade selection molecular dynamics (LB-PaCS-MD) simulations was employed to elucidate plausible paths and conformations of ebselen, a synthetic organoselenium drug, within the Mpro catalytic site. Ebselen effectively engaged the active site, adopting proximity to H41 and interacting through the benzoisoselenazole ring in a π-π T -shaped arrangement, with an additional π-sulfur interaction with C145. In addition, the ligand-based drug design using the QSAR with GFA-MLR, RF, and ANN models were employed for biological activity prediction. The QSAR-ANN model showed robust statistical performance, with an r2 training exceeding 0.98 and an RMSE test of 0.21, indicating its suitability for predicting biological activities. Integration the ANN model with the LB-PaCS-MD insights enabled the rational design of novel compounds anchored in the ebselen core structure, identifying promising candidates with favorable predicted IC 50 values. The designed compounds exhibited suitable drug-like characteristics and adopted an active conformation similar to ebselen, inhibiting Mpro function. These findings represent a synergistic approach merging ligand and structure-based drug design; with the potential to guide experimental synthesis and enzyme assay testing. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 main protease (Mpro) is a well-recognized target for COVID-19 therapy. Green tea (−)-epigallocatechin-3-gallate (EGCG) possesses Mpro-inhibitory activity; however, the influence of EGCG oxidation on its inhibition activity remains obscure, given its high oxidation propensity. This study reveals that prolonged EGCG oxidation in the presence of Mpro dramatically increases its inhibitory activity with an IC 50 of 0.26 μM. The inhibitory mechanism is that EGCG-quinone preferentially binds the active site Mpro-Cys145-SH, which forms a quinoprotein. Though Mpro is present in the cell lysate, EGCG preferentially depletes its thiols. Non-cytotoxic EGCG effectively generates a quinoprotein in living cells, thus EGCG might selectively inhibit Mpro in SARS-CoV-2 infected cells. Chlorogenic acid facilitates EGCG oxidation. Together, they synergistically deplete multiple Mpro thiols though this is not more beneficial than EGCG alone. By contrast, excessive EGCG oxidation prior to incubation with Mpro largely compromises its inhibitory activity. Overall, the low IC 50 and the high selectivity imply that EGCG is a promising dietary Mpro inhibitor. While EGCG oxidation in the presence of Mpro has a pivotal role in inhibition, enhancing EGCG oxidation by chlorogenic acid no longer increases its inhibitory potential. EGCG oxidation in the absence of Mpro should be avoided to maximize its Mpro-inhibitory activity. [Display omitted] • Prolonged EGCG oxidation in the presence of Mpro greatly increases its inhibitory activity. • Mpro inhibition by EGCG is closely linked to quinoprotein formation. • Among the 12 cysteinyl thiols in Mpro, EGCG preferentially binds the active site Cys145-SH. • EGCG and its oxidation catalyst, CGA, synergistically reduce Mpro thiols but not Mpro activity. • Prolonged EGCG oxidation prior to incubation with Mpro reduces inhibitory capacity. [ABSTRACT FROM AUTHOR]

The assembly of two monomeric constructs spanning segments 1-199 (MPro 1-199 ) and 10-306 (MPro 10-306 ) of SARS-CoV-2 main protease (MPro) was examined to assess the existence of a transient heterodimer intermediate in the N-terminal autoprocessing pathway of MPro model precursor. Together, they form a heterodimer population accompanied by a 13-fold increase in catalytic activity. Addition of inhibitor GC373 to the proteins increases the activity further by ∼7-fold with a 1:1 complex and higher order assemblies approaching 1:2 and 2:2 molecules of MPro 1-199 and MPro 10-306 detectable by analytical ultracentrifugation and native mass estimation by light scattering. Assemblies larger than a heterodimer (1:1) are discussed in terms of alternate pathways of domain III association, either through switching the location of helix 201 to 214 onto a second helical domain of MPro 10-306 and vice versa or direct interdomain III contacts like that of the native dimer, based on known structures and AlphaFold 3 prediction, respectively. At a constant concentration of MPro 1-199 with molar excess of GC373, the rate of substrate hydrolysis displays first order dependency on the MPro 10-306 concentration and vice versa. An equimolar composition of the two proteins with excess GC373 exhibits half-maximal activity at ∼6 μM MPro 1-199 . Catalytic activity arises primarily from MPro 1-199 and is dependent on the interface interactions involving the N-finger residues 1 to 9 of MPro 1-199 and E290 of MPro 10-306 . Importantly, our results confirm that a single N-finger region with its associated intersubunit contacts is sufficient to form a heterodimeric MPro intermediate with enhanced catalytic activity., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Published by Elsevier Inc.)

Viral infections cause significant health problems all over the world, and it is critical to develop treatments for these problems. Antivirals that target viral genome-encoded proteins frequently cause the virus to become more resistant to treatment. Because viruses rely on several cellular proteins and phosphorylation processes that are essential to their life cycle, drugs targeting host-based targets could be a viable treatment option. To reduce costs and improve efficiency, existing kinase inhibitors could be repurposed as antiviral medications; however, this method rarely works, and specific biophysical approaches are required in the field. Because of the widespread use of FDA-approved kinase inhibitors, it is now possible to better understand how host kinases contribute to viral infection. The purpose of this article is to investigate the tyrphostin AG879 (Tyrosine kinase inhibitor) binding information in Bovine Serum Albumin (BSA), human ErbB2 (HER2), C-RAF1 Kinase (c-RAF), SARS-CoV-2 main protease (COVID 19), and Angiotensin-converting enzyme 2 (ACE-2).Communicated by Ramaswamy H. Sarma.

The Coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) has become a global health crisis, and the urgent need for effective treatments is evident. One potential target for COVID-19 therapeutics is the main protease (Mpro) of SARS‑CoV‑2, an essential enzyme for viral replication. Natural compounds have been explored as a source of potential inhibitors for Mpro due to their safety and availability. In this study, we employed a computational approach to screen a library of phytoconstituents and identified potential Mpro inhibitors based on their binding affinities and molecular interactions. The top-ranking compounds were further validated through molecular dynamics simulations (MDS) and free energy calculations. As a result of the above procedures, we identified two phytoconstituents, Khelmarin B and Neogitogenin, with appreciable binding affinity and specificity towards the Mpro binding pocket. Our results suggest that Khelmarin B and Neogitogenin could potentially serve as Mpro inhibitors and have the potential to be developed as COVID-19 therapeutics. Further experimental studies are required to confirm the efficacy and safety of these compounds.Communicated by Ramaswamy H. Sarma.