Chrysin 7-O-ß-D-glucuronide, a dual inhibitor of SARS-CoV-2 3CLpro and PLpro, for the prevention and treatment of COVID-19.

The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) resulted in the coronavirus disease 2019 (COVID-19) pandemic. Given the advent of subvariants, there is an urgent need to develop novel drugs. The aim of this study was to find SARS-CoV-2 inhibitors from Scutellaria baicalensis Georgi targeting the proteases 3CLpro and PLpro. After screening 25 flavonoids, chrysin 7-O-ß-D-glucuronide was found to be a potent inhibitor of SARS-CoV-2 on Vero E6 cells, with half-maximal effective concentration of 8.72 µM. Surface plasmon resonance assay, site-directed mutagenesis and enzymatic activity measurements indicated that chrysin-7-O-ß-D-glucuronide inhibits SARS-CoV-2 by binding to H41 of 3CLpro, and K157 and E167 of PLpro. Hydrogen-deuterium exchange mass spectrometry analysis showed that chrysin-7-O-ß-D-glucuronide changes the conformation of PLpro. Finally, chrysin 7-O-ß-D-glucuronide was shown to have anti-inflammatory activity, mainly due to reduction of the levels of the pro-inflammatory cytokines interleukin (IL)-1ß and IL-6.

Derivation, Functionalization of (S)-Goniothalamin from Goniothalamus wightii and Their Derivative Targets SARS-CoV-2 MPro, SPro, and RdRp: A Pharmacological Perspective.

The tracing of an alternative drug, Phytochemicals is a promising approach to the viral threats that have emerged over the past two years. Across the world, herbal medicine is a better solution against anti-viral diseases during pandemic periods. Goniothalamus wightii is an herbal plant, which has diverse bioactive compounds with anticancer, antioxidant, and anti-viral properties. The aim of the study was to isolate the compound by chromatography studies and functionalization by FT-IR, LC-MS, and NMR (C-NMR, H-NMR). As a result, the current work focuses on whether (S)-Goniathalamin and its analogue could act as natural anti-viral molecules for multiple target proteins viz., MPro, RdRp, and SPro, which are required for SARS-CoV-2 infection. Overall, 954 compounds were examined and the molecular-docking studies were performed on the maestro platform of Schrodinger software. Molecular-dynamics simulation studies were performed on two complex major compounds to confirm their affinity across 150 simulations. This research suggests that plant-based drugs have high levels of antiviral properties against coronavirus. However, more research is needed to verify its antiviral properties.

Actinidin diversity: discovery of common and selective substrates for actinidin isoforms and Actinidia cultivars.

The actinidin proteinase family has a striking sequence diversity; isoelectric points range from 3.9 to 9.3. The biological drive for this variation is thought to be actinidin's role as a defense-related protein. In this study we map mutations in the primary sequence onto the 3D structure of the protein and show that the region with the highest diversity is close to the substrate binding groove. Non-conservative substitutions in the active site determine substrate preference and therefore create problems for quantification of actinidin activity. Here we use a peptide substrate library to compare two actinidin isoforms, one from the kiwiberry cultivar 'Hortgem Tahi' (Actinidia arguta), and the other from the familiar kiwifruit cultivar 'Hayward' (Actinidia chinensis var. deliciosa). Among 360 octamer substrates we find one substrate (RVAAGSPI) with the useful property of being readily cleaved by all the functionally active actinidins in a set of A. arguta and A. chinensis var. deliciosa isoforms. In addition, we find that two substrates (LPPKSQPP & ILRDKDNT) have the ability to differentiate different isoforms from a single fruit. We compare actinidins from 'Hayward' and A. arguta for their ability to digest the allergenic gluten peptide (PFPQPQLPY) but find the peptide to be indigestible by all sources of actinidin. The ability to inactivate salivary amylase is shown to be a common trait in Actinidia cultivars due to proteolysis by actinidin and is particularly strong in 'Hortgem Tahi'. A mixture of 10% 'Hortgem Tahi' extract with 90% saliva inactivates 100% of amylase activity within 5 minutes. Conceivably, 'Hortgem Tahi' might lower the glycaemic response in a meal rich in cooked starch.

In Silico Studies on Zinc Oxide Based Nanostructured Oil Carriers with Seed Extracts of Nigella sativa and Pimpinella anisum as Potential Inhibitors of 3CL Protease of SARS-CoV-2.

Coming into the second year of the pandemic, the acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants continue to be a serious health hazard globally. A surge in the omicron wave, despite the discovery of the vaccines, has shifted the attention of research towards the discovery and use of bioactive compounds, being potential inhibitors of the viral structural proteins. The present study aimed at the green synthesis of zinc oxide (ZnO) nanoparticles with seed extracts of Nigella sativa and Pimpinella anisum-loaded nanostructured oil carriers (NLC)-using a mixture of olive and black seed essential oils. The synthesized ZnO NLC were extensively characterized. In addition, the constituent compounds in ZnO NLC were investigated as a potential inhibitor for the SARS-CoV-2 main protease (3CLpro or Mpro) where 27 bioactive constituents, along with ZnO in the nanostructure, were subjected to molecular docking studies. The resultant high-score compounds were further validated by molecular dynamics simulation. The study optimized the compounds dithymoquinone, δ-hederin, oleuropein, and zinc oxide with high docking energy scores (ranging from -7.9 to -9.9 kcal/mol). The RMSD and RMSF data that ensued also mirrored these results for the stability of proteins and ligands. RMSD and RMSF data showed no conformational change in the protein during the MD simulation. Histograms of every simulation trajectory explained the ligand properties and ligand-protein contacts. Nevertheless, further experimental investigations and validation of the selected candidates are imperative to take forward the applicability of the nanostructure as a potent inhibitor of COVID-19 (Coronavirus Disease 2019) for clinical trials.

Investigation of the inhibitory activity of some dietary bioactive flavonoids against SARS-CoV-2 using molecular dynamics simulations and MM-PBSA calculations.

Eventhough the development of vaccine against COVID-19 pandemic is progressing in different part of the world a well-defined treatment plan is not yet developed. Therefore, we investigate the inhibitory activity of a group of dietary bioactive flavonoids against SARS-CoV-2 main protease (Mpro), which are identified as one of the potential targets in the drug discovery process of COVID-19. After the initial virtual screening of a number of bioactive flavonoids, the binding affinity of three compounds - Naringin, Naringenin and Amentoflavone - at the active site of Mpro was investigated through MD Simulations, MM-PBSA and DFT Binding Energy calculations. From the MD trajectory analysis, Amentoflavone and Naringin showed consistent protein-ligand interactions with the aminoacid residues of the active site domains of Mpro. The excellent inhibitory activity of Amentoflavone and Naringin was established from its MM-PBSA binding energy values of -190.50 and -129.87 kJ/mol respectively. The MET165 residue of Mpro is identified as one of the key residue which contributed significantly to MM-PBSA binding energy through hydrophobic interactions. Furthermore, the DFT binding energy values of Amentoflavone (-182.92 kJ/mol) and Naringin (-160.67 kJ/mol) in active site molecular clusters with hydrogen bonds confirmed their potential inhibitory activity. These compounds are of high interest because of their wide availability, low cost, no side effects, and long history of use. We can prevent the severity of this disease for home care patients using these effective dietary supplements. We are hopeful that our results have implications for the development of prophylaxis of COVID-19.Communicated by Ramaswamy H. Sarma.

X-ray Structure Determination, Antioxidant Voltammetry Studies of Butein and 2',4'-Dihydroxy-3,4-dimethoxychalcone. Computational Studies of 4 Structurally Related 2',4'-diOH Chalcones to Examine Their Antimalarial Activity by Binding to Falcipain-2.

Malaria is a huge global health burden with resistance to currently available medicines resulting in the search for newer antimalarial compounds from traditional medicinal plants in malaria-endemic regions. Previous studies on two chalcones, homobutein and 5-prenylbutein, present in E. abyssinica, have shown moderate antiplasmodial activity. Here, we describe results from experimental and computational investigations of four structurally related chalcones, butein, 2',4'-dihydroxy-3,4-dimethoxychalcone (DHDM), homobutein and 5-prenylbutein to elucidate possible molecular mechanisms by which these compounds clear malaria parasites. The crystal structures of butein and DHDM show that butein engages in more hydrogen bonding and consequently, more intermolecular interactions than DHDM. Rotating ring-disk electrode (RRDE) voltammetry results show that butein has a higher antioxidant activity towards the superoxide radical anion compared to DHDM. Computational docking experiments were conducted to examine the inhibitory potential of all four compounds on falcipain-2, a cysteine protease that is involved in the degradation of hemoglobin in plasmodium-infected red blood cells of the host. Overall, this work suggests butein as a better antimalarial compound due to its structural features which allow it to have greater intermolecular interactions, higher antioxidant activity and to create a covalent complex at the active site of falcipain-2.

Virus and helper component interactions favour the transmission of recombinant potato virus Y strains.

In recent years, several recombinant strains of potato virus Y, notably PVYNTN and PVYN:O have displaced the ordinary strain, PVYO, and emerged as the predominant strains affecting the USA potato crop. Previously we reported that recombinant strains were transmitted more efficiently than PVYO when they were acquired sequentially, regardless of acquisition order. In another recent study, we showed that PVYNTN binds preferentially to the aphid stylet over PVYO when aphids feed on a mixture of PVYO and PVYNTN. To understand the mechanism of this transmission bias as well as preferential virus binding, we separated virus and active helper component proteins (HC), mixed them in homologous and heterologous combinations, and then fed them to aphids using Parafilm sachets. Mixtures of PVYO HC with either PVYN:O or PVYNTN resulted in efficient transmission. PVYN:O HC also facilitated the transmission of PVYO and PVYNTN, albeit with reduced efficiency. PVYNTN HC failed to facilitate transmission of either PVYO or PVYN:O. When PVYO HC or PVYN:O HC was mixed with equal amounts of the two viruses, both viruses in all combinations were transmitted at high efficiencies. In contrast, no transmission occurred when combinations of viruses were mixed with PVYNTN HC. Further study evaluated transmission using serial dilutions of purified virus mixed with HCs. While PVYNTN HC only facilitated the transmission of the homologous virus, the HCs of PVYO and PVYN:O facilitated the transmission of all strains tested. This phenomenon has likely contributed to the increase in the recombinant strains affecting the USA potato crop.

Searching for target-specific and multi-targeting organics for Covid-19 in the Drugbank database with a double scoring approach.

The current outbreak of Covid-19 infection due to SARS-CoV-2, a virus from the coronavirus family, has become a major threat to human healthcare. The virus has already infected more than 44 M people and the number of deaths reported has reached more than 1.1 M which may be attributed to lack of medicine. The traditional drug discovery approach involves many years of rigorous research and development and demands for a huge investment which cannot be adopted for the ongoing pandemic infection. Rather we need a swift and cost-effective approach to inhibit and control the viral infection. With the help of computational screening approaches and by choosing appropriate chemical space, it is possible to identify lead drug-like compounds for Covid-19. In this study, we have used the Drugbank database to screen compounds against the most important viral targets namely 3C-like protease (3CLpro), papain-like protease (PLpro), RNA-dependent RNA polymerase (RdRp) and the spike (S) protein. These targets play a major role in the replication/transcription and host cell recognition, therefore, are vital for the viral reproduction and spread of infection. As the structure based computational screening approaches are more reliable, we used the crystal structures for 3C-like main protease and spike protein. For the remaining targets, we used the structures based on homology modeling. Further, we employed two scoring methods based on binding free energies implemented in AutoDock Vina and molecular mechanics-generalized Born surface area approach. Based on these results, we propose drug cocktails active against the three viral targets namely 3CLpro, PLpro and RdRp. Interestingly, one of the identified compounds in this study i.e. Baloxavir marboxil has been under clinical trial for the treatment of Covid-19 infection. In addition, we have identified a few compounds such as Phthalocyanine, Tadalafil, Lonafarnib, Nilotinib, Dihydroergotamine, R-428 which can bind to all three targets simultaneously and can serve as multi-targeting drugs. Our study also included calculation of binding energies for various compounds currently under drug trials. Among these compounds, it is found that Remdesivir binds to targets, 3CLpro and RdRp with high binding affinity. Moreover, Baricitinib and Umifenovir were found to have superior target-specific binding while Darunavir is found to be a potential multi-targeting drug. As far as we know this is the first study where the compounds from the Drugbank database are screened against four vital targets of SARS-CoV-2 and illustrates that the computational screening using a double scoring approach can yield potential drug-like compounds against Covid-19 infection.

Structure-based lead optimization of herbal medicine rutin for inhibiting SARS-CoV-2's main protease.

Coronavirus disease 2019 (COVID-19) is an ongoing global pandemic with very limited specific treatments. To fight COVID-19, various traditional antiviral medicines have been prescribed in China to infected patients with mild to moderate symptoms and received unexpected success in controlling the disease. However, the molecular mechanisms of how these herbal medicines interact with the SARS-CoV-2 virus that causes COVID-19 have remained elusive. It is well known that the main protease (Mpro) of SARS-CoV-2 plays an important role in maturation of many viral proteins such as the RNA-dependent RNA polymerase. Here, we explore the underlying molecular mechanisms of the computationally determined top candidate, namely, rutin which is a key component in many traditional antiviral medicines such as Lianhuaqinwen and Shuanghuanlian, for inhibiting the viral target-Mpro. Using in silico methods (docking and molecular dynamics simulations), we revealed the dynamics and energetics of rutin when interacting with the Mpro of SARS-CoV-2, suggesting that the highly hydrophilic rutin molecule can be bound inside the Mpro's pocket (active site) and possibly inhibit its biological functions. In addition, we optimized the structure of rutin and designed two more hydrophobic analogs, M1 and M2, which satisfy the rule of five for western medicines and demonstrated that they (M2 in particular) possess much stronger binding affinities to the SARS-COV-2s Mpro than rutin, due to the enhanced hydrophobic interaction as well as more hydrogen bonds. Therefore, our results provide invaluable insights into the mechanism of a ligand's binding inside the Mpro and shed light on future structure-based designs of high-potent inhibitors for SARS-CoV-2 Mpro.

Structures of the free and inhibitors-bound forms of bromelain and ananain from Ananas comosus stem and in vitro study of their cytotoxicity.

The Ananas comosus stem extract is a complex mixture containing various cysteine ​​proteases of the C1A subfamily, such as bromelain and ananain. This mixture used for centuries in Chinese medicine, has several potential therapeutic applications as anti-cancer, anti-inflammatory and ecchymosis degradation agent. In the present work we determined the structures of bromelain and ananain, both in their free forms and in complex with the inhibitors E64 and TLCK. These structures combined with protease-substrate complexes modeling clearly identified the Glu68 as responsible for the high discrimination of bromelain in favor of substrates with positively charged residues at P2, and unveil the reasons for its weak inhibition by cystatins and E64. Our results with purified and fully active bromelain, ananain and papain show a strong reduction of cell proliferation with MDA-MB231 and A2058 cancer cell lines at a concentration of about 1 µM, control experiments clearly emphasizing the need for proteolytic activity. In contrast, while bromelain and ananain had a strong effect on the proliferation of the OCI-LY19 and HL-60 non-adherent cell lines, papain, the archetypal member of the C1A subfamily, had none. This indicates that, in this case, sequence/structure identity beyond the active site of bromelain and ananain is more important than substrate specificity.

Biochemical screening for SARS-CoV-2 main protease inhibitors.

The Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) pandemic represents a global challenge. SARS-CoV-2's ability to replicate in host cells relies on the action of its non-structural proteins, like its main protease (Mpro). This cysteine protease acts by processing the viruses' precursor polyproteins. As proteases, together with polymerases, are main targets of antiviral drug design, we here have performed biochemical high throughput screening (HTS) with recombinantly expressed SARS-CoV-2 Mpro. A fluorescent assay was used to identify inhibitors in a compound library containing known drugs, bioactive molecules and natural products. These screens led to the identification of 13 inhibitors with IC50 values ranging from 0.2 µM to 23 µM. The screens confirmed several known SARS-CoV Mpro inhibitors as inhibitors of SARS-CoV-2 Mpro, such as the organo-mercuric compounds thimerosal and phenylmercuric acetate. Benzophenone derivatives could also be identified among the most potent screening hits. Additionally, Evans blue, a sulfonic acid-containing dye, could be identified as an Mpro inhibitor. The obtained compounds could be of interest as lead compounds for the development of future SARS-CoV-2 drugs.

Andrographolide and its fluorescent derivative inhibit the main proteases of 2019-nCoV and SARS-CoV through covalent linkage.

The coronavirus disease 2019 (COVID-19) pandemic caused by 2019 novel coronavirus (2019-nCoV) has been a crisis of global health, whereas the effective vaccines against 2019-nCoV are still under development. Alternatively, utilization of old drugs or available medicine that can suppress the viral activity or replication may provide an urgent solution to suppress the rapid spread of 2019-nCoV. Andrographolide is a highly abundant natural product of the medicinal plant, Andrographis paniculata, which has been clinically used for inflammatory diseases and anti-viral therapy. We herein demonstrate that both andrographolide and its fluorescent derivative, the nitrobenzoxadiazole-conjugated andrographolide (Andro- NBD), suppressed the main protease (Mpro) activities of 2019-nCoV and severe acute respiratory syndrome coronavirus (SARS-CoV). Moreover, Andro-NBD was shown to covalently link its fluorescence to these proteases. Further mass spectrometry (MS) analysis suggests that andrographolide formed a covalent bond with the active site Cys145 of either 2019-nCoV Mpro or SARS-CoV Mpro. Consistently, molecular modeling analysis supported the docking of andrographolide within the catalytic pockets of both viral Mpros. Considering that andrographolide is used in clinical practice with acceptable safety and its diverse pharmacological activities that could be beneficial for attenuating COVID-19 symptoms, extensive investigation of andrographolide on the suppression of 2019-nCoV as well as its application in COVID-19 therapy is suggested.

Thermostable and alkalistable exopolygalacturonase of Bacillus pumilus dcsr1: Characteristics and applicability.

The bioactive form of thermostable and alkali stable pectinase of Bacillus pumilus dcsr1 is a homodimer of the molecular mass of 60 kDa with a pI of 4.6. The enzyme is optimally active at 50 °C and pH 10.5, and its Michaelis constant (Km), maximum rate of reaction (Vmax), activation energy (Ea), and temperature quotient (Q10) values (for citrus pectin) are 0.29 mg mL-1, 116 µmole mg-1 min-1, 74.73 KJmol-1 and 1.57, respectively. The enzyme has a shelf life of one and a half years at room temperature as well as 4 °C. The activity of the enzyme is stimulated by Mn2+ and Ca2+ and inhibited by Hg+, Cd2+, Co2+, Zn2+, Fe2+, Pb2+, EDTA and urea to a varied extent. The conformational studies of the enzyme revealed a high ß-sheet content in the bioactive dimer, and high α-helix in the inactive monomer. The Circular Dichroism (CD) spectra of the dimer in the presence of inhibitors suggested a marked decrease in ß-sheet, and a significant increase in α-helix, suggesting a key role of ß-sheets in the enzyme catalysis. Based on the end product analysis, the enzyme is an exopolygalacturonase with a unique ability of transglycosylation. When ramie fibers were treated with the enzyme, removal of gummy material (pectin) was visible, confirming its applicability in the degumming process.

Structural-based virtual screening and in vitro assays for small molecules inhibiting the feline coronavirus 3CL protease as a surrogate platform for coronaviruses.

Feline infectious peritonitis (FIP) which is caused by feline infectious peritonitis virus (FIPV), a variant of feline coronavirus (FCoV), is a member of family Coronaviridae, together with severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and SARS-CoV-2. So far, neither effective vaccines nor approved antiviral therapeutics are currently available for the treatment of FIPV infection. Both human and animal CoVs shares similar functional proteins, particularly the 3CL protease (3CLpro), which plays the pivotal role on viral replication. We investigated the potential drug-liked compounds and their inhibitory interaction on the 3CLpro active sites of CoVs by the structural-bases virtual screening. Fluorescence resonance energy transfer (FRET) assay revealed that three out of twenty-eight compounds could hamper FIPV 3CLpro activities with IC50 of 3.57 ± 0.36 µM to 25.90 ± 1.40 µM, and Ki values of 2.04 ± 0.08 to 15.21 ± 1.76 µM, respectively. Evaluation of antiviral activity using cell-based assay showed that NSC629301 and NSC71097 could strongly inhibit the cytopathic effect and also reduced replication of FIPV in CRFK cells in all examined conditions with the low range of EC50 (6.11 ± 1.90 to 7.75 ± 0.48 µM and 1.99 ± 0.30 to 4.03 ± 0.60 µM, respectively), less than those of ribavirin and lopinavir. Analysis of FIPV 3CLpro-ligand interaction demonstrated that the selected compounds reacted to the crucial residues (His41 and Cys144) of catalytic dyad. Our investigations provide a fundamental knowledge for the further development of antiviral agents and increase the number of anti-CoV agent pools for feline coronavirus and other related CoVs.

Laser irradiated phenothiazines: New potential treatment for COVID-19 explored by molecular docking.

The worldwide infection with the new Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) demands urgently new potent treatment(s). In this study we predict, using molecular docking, the binding affinity of 15 phenothiazines (antihistaminic and antipsychotic drugs) when interacting with the main protease (Mpro) of SARS-CoV-2. Additionally, we tested the binding affinity of photoproducts identified after irradiation of phenothiazines with Nd:YAG laser beam at 266 nm respectively 355 nm. Our results reveal that thioridazine and its identified photoproducts (mesoridazine and sulforidazine) have high biological activity on the virus Mpro. This shows that thioridazine and its two photoproducts might represent new potent medicines to be used for treatment in this outbreak. Such results recommend these medicines for further tests on cell cultures infected with SARS-CoV-2 or animal model. The transition to human subjects of the suggested treatment will be smooth due to the fact that the drugs are already available on the market.

Molecular modelling investigation for drugs and nutraceuticals against protease of SARS-CoV-2.

The widespread problem of a 2019-novel coronavirus (SARS-CoV-2) strain outbreak in Wuhan, China has prompted a search for new drugs to protect against and treat this disease. It is necessary to immediately investigate this due to the mutation of the viral genome and there being no current protective vaccines or therapeutic drugs. Molecular modelling and molecular docking based on in silico screening strategies were employed to determine the potential activities of seven HIV protease (HIV-PR) inhibitors, two flu drugs, and eight natural compounds. The computational approach was carried out to discover the structural modes with a high binding affinity for these drugs on the homology structure of the Wuhan coronavirus protease (SARS-CoV-2 PR). From the theoretical calculations, all the drugs and natural compounds demonstrated various favorable binding affinities. An interesting finding was that the natural compounds tested had a higher potential binding activity with the pocket sites of SARS-CoV-2 PR compared to the groups of HIV-PR inhibitors. The binding modes of each complex illustrated between the drugs and compounds interacted with the functional group of amino acids in the binding pocket via hydrophilic, hydrophobic, and hydrogen bond interactions using the molecular dynamics simulation technique. This result supports the idea that existing protease inhibitors and natural compounds could be used to treat the new coronavirus. This report sought to provide fundamental knowledge as preliminary experimental data to propose an existing nutraceutical material against viral infection. Collectively, it is suggested that molecular modelling and molecular docking are suitable tools to search and screen for new drugs and natural compounds that can be used as future treatments for viral diseases.

In silico Potential of Approved Antimalarial Drugs for Repurposing Against COVID-19.

Although the coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is wreaking havoc and resulting in mortality and morbidity across the planet, novel treatments are urgently needed. Drug repurposing offers an innovative approach in this context. We report here new findings on the in silico potential of several antimalarial drugs for repurposing against COVID-19. We conducted analyses by docking the compounds against two SARS-CoV-2-specific targets: (1) the receptor binding domain spike protein and (2) the main protease of the virus (MPro) using the Schrödinger software. Importantly, the docking analysis revealed that doxycycline (DOX) showed the most effective binding to the spike protein of SARS-CoV-2, whereas halofantrine and mefloquine bound effectively with the main protease among the antimalarial drugs evaluated in the present study. The in silico approach reported here suggested that DOX could potentially be a good candidate for repurposing for COVID-19. In contrast, to decipher the actual potential of DOX and halofantrine against COVID-19, further in vitro and in vivo studies are called for. Drug repurposing warrants consideration as a viable research and innovation avenue as planetary health efforts to fight the COVID-19 continue.

Bioactive Indolyl Diketopiperazines from the Marine Derived Endophytic Aspergillus versicolor DY180635.

Four new indolyl diketopiperazines, aspamides A-E (1-4) and two new diketopiperazines, aspamides F-G (5-6), along with 11 known diketopiperazines and intermediates were isolated from the solid culture of Aspergillus versicolor, which is an endophyte with the sea crab (Chiromantes haematocheir). Further chiral high-performance liquid chromatography resolution gave enantiomers (+)- and (-)-4, respectively. The structures and absolute configurations of compounds 1-6 were determined by the comprehensive analyses of nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), and electronic circular dichroism (ECD) calculation. All isolated compounds were selected for the virtual screening on the coronavirus 3-chymoretpsin-like protease (Mpro) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and the docking scores of compounds 1-2, 5, 6, 8 and 17 were top among all screened molecules, may be helpful in fighting with Corona Virus Disease-19 (COVID-19) after further studies.

Virtual screening of approved drugs as potential SARS-CoV-2 main protease inhibitors.

The global emergency caused by COVID-19 makes the discovery of drugs capable of inhibiting SARS-CoV-2 a priority, to reduce the mortality and morbidity of this disease. Repurposing approved drugs can provide therapeutic alternatives that promise rapid and ample coverage because they have a documented safety record, as well as infrastructure for large-scale production. The main protease of SARS-CoV-2 (Mpro) is an excellent therapeutic target because it is critical for viral replication; however, Mpro has a highly flexible active site that must be considered when performing computer-assisted drug discovery. In this work, potential inhibitors of the main protease (Mpro) of SARS-Cov-2 were identified through a docking-assisted virtual screening procedure. A total of 4384 drugs, all approved for human use, were screened against three conformers of Mpro. The ligands were further studied through molecular dynamics simulations and binding free energy analysis. A total of nine currently approved molecules are proposed as potential inhibitors of SARS-CoV-2. These molecules can be further tested to speed the development of therapeutics against COVID-19.

Virtual screening based on molecular docking of possible inhibitors of Covid-19 main protease.

Coronavirus (COVID-19) is an enveloped RNA virus that is diversely found in humans and that has now been declared a global pandemic by the World Health Organization. Thus, there is an urgent need to develop effective therapies and vaccines against this disease. In this context, this study aimed to evaluate in silico the molecular interactions of drugs with therapeutic indications for treatment of COVID-19 (Azithromycin, Baricitinib and Hydroxychloroquine) and drugs with similar structures (Chloroquine, Quinacrine and Ruxolitinib) in docking models from the SARS-CoV-2 main protease (M-pro) protein. The results showed that all inhibitors bound to the same enzyme site, more specifically in domain III of the SARS-CoV-2 main protease. Therefore, this study allows proposing the use of baricitinib and quinacrine, in combination with azithromycin; however, these computer simulations are just an initial step for conceiving new projects for the development of antiviral molecules.