Computational investigation on the antioxidant activities and on the Mpro SARS-CoV-2 non-covalent inhibition of isorhamnetin.

In the present work, we report a computational study on some important chemical properties of the flavonoid isorhamnetin, used in traditional medicine in many countries. In the course of the study we determined the acid-base equilibria in aqueous solution, the possible reaction pathways with the •OOH radical and the corresponding kinetic constants, the complexing capacity of copper ions, and the reduction of these complexes by reducing agents such as superoxide and ascorbic anion by using density functional level of theory Density Functional Theory. Finally, the non-covalent inhibition ability of the SARS-CoV-2 main protease enzyme by isorhamnetin was examined by molecular dynamics (MD) and docking investigation.

SARS-CoV-2 Main Protease Inhibitors: Structure-Based Enhancement to Anti-Viral Pre-Clinical GC376 Encourages Further Development

SARS-CoV-2 Main protease (Mpro) is pivotal in viral replication and transcription. Mpro mediates proteolysis of translated products of replicase genes ORF1a and ORF1ab. Surveying pre-clinical trial Mpro inhibitors suggests potential enhanced efficacy for some moieties. Concordant with promising in vitro and in silico data, the protease inhibitor GC376 was chosen as a lead. Modification of GC376 analogues yielded a series of promising Mpro inhibitors. Design optimization identified compound G59i as lead candidate, displaying a binding energy of −10.54kcal/mol for the complex. Robust interactivity was noted between G59i and Mpro. With commendable ADMET characteristics and enhanced potency, further G59i analysis may be advantageous;moreover, identified key Mpro residues could contribute to the design of neotenic inhibitors. [ FROM AUTHOR]

Quercetin as a possible complementary agent for early-stage COVID-19: Concluding results of a randomized clinical trial.

Background: Quercetin, a natural polyphenol with demonstrated broad-spectrum antiviral, anti-inflammatory, and antioxidant properties, has been proposed as an adjuvant for early-stage coronavirus disease 2019 (COVID-19) infection. Objective: To explore the possible therapeutic effect of quercetin in outpatients with early-stage mild to moderate symptoms of COVID-19. Methods: This was an open-label randomized controlled clinical trial conducted at the department of medicine, King Edward Medical University, Lahore, PK. Patients were randomized to receive either standard of care (SC) plus an oral quercetin supplement (500 mg Quercetin Phytosome®, 1st week, TDS: 2nd week, BDS) (n = 50, quercetin group) or SC alone (n = 50, control group). Results: After one week of treatment, patients in the quercetin group showed a speedy recovery from COVID-19 as compared to the control group, i.e., 34 patients (vs. 12 in the control group) tested negative for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (p = 0.0004), and 26 patients (vs. 12 in the control group) had their COVID-19-associated acute symptoms resolved (p = 0.0051). Patients in the quercetin group also showed a significant fall in the serum lactate dehydrogenase (LDH) mean values i.e., from 406.56 ± 183.92 to 257.74 ± 110.73 U/L, p = 0.0001. Quercetin was well-tolerated by all the 50 patients, and no side effects were reported. Conclusion: Our results, suggest the possible therapeutic role of quercetin in early-stage COVID-19, including speedy clearance of SARS-CoV-2, early resolution of the acute symptoms and modulation of the host's hyperinflammatory response. Clinical Trial Registration: clinicaltrials.gov, identifier NCT04861298.

Celastrol: A lead compound that inhibits SARS-CoV-2 replication, the activity of viral and human cysteine proteases, and virus-induced IL-6 secretion.

The global emergence of coronavirus disease 2019 (COVID-19) has caused substantial human casualties. Clinical manifestations of this disease vary from asymptomatic to lethal, and the symptomatic form can be associated with cytokine storm and hyperinflammation. In face of the urgent demand for effective drugs to treat COVID-19, we have searched for candidate compounds using in silico approach followed by experimental validation. Here we identified celastrol, a pentacyclic triterpene isolated from Tripterygium wilfordii Hook F, as one of the best compounds out of 39 drug candidates. Celastrol reverted the gene expression signature from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected cells and irreversibly inhibited the recombinant forms of the viral and human cysteine proteases involved in virus invasion, such as Mpro (main protease), PLpro (papain-like protease), and recombinant human cathepsin L. Celastrol suppressed SARS-CoV-2 replication in human and monkey cell lines and decreased interleukin-6 (IL-6) secretion in the SARS-CoV-2-infected human cell line. Celastrol acted in a concentration-dependent manner, with undetectable signs of cytotoxicity, and inhibited in vitro replication of the parental and SARS-CoV-2 variant. Therefore, celastrol is a promising lead compound to develop new drug candidates to face COVID-19 due to its ability to suppress SARS-CoV-2 replication and IL-6 production in infected cells.

Host Cell Proteases Mediating SARS-CoV-2 Entry: An Overview.

The outbreak of the SARS-CoV-2 virus in late 2019 and the spread of the COVID-19 pandemic have caused severe health and socioeconomic damage worldwide. Despite the significant research effort to develop vaccines, antiviral treatments, and repurposed therapeutics to effectively contain the catastrophe, there are no available effective vaccines or antiviral drugs that can limit the threat of the disease, so the infections continue to expand. To date, the search for effective treatment remains a global challenge. Therefore, it is imperative to develop therapeutic strategies to contain the spread of SARS-CoV-2. Like other coronaviruses, SARS-CoV-2 invades and infects human host cells via the attachment of its spike envelope glycoprotein to the human host cell receptor hACE2. Subsequently, several host cell proteases facilitate viral entry via proteolytic cleavage and activation of the S protein. These host cell proteases include type II transmembrane serine proteases (TTSPs), cysteine cathepsins B and L, furin, trypsin, and Factor Xa, among others. Given the critical role of the host cell proteases in coronavirus pathogenesis, their inhibition by small molecules has successfully targeted SARS-CoV-2 in vitro, suggesting that host cell proteases are attractive therapeutic targets for SARS-CoV-2 infection. In this review, we focus on the biochemical properties of host cell proteases that facilitate the entry of SARS-CoV-2, and we highlight therapeutic small molecule candidates that have been proposed through in silico research.

Mass Spectrometric Assays Reveal Discrepancies in Inhibition Profiles for the SARS-CoV-2 Papain-Like Protease.

The two SARS-CoV-2 proteases, i. e. the main protease (Mpro ) and the papain-like protease (PLpro ), which hydrolyze the viral polypeptide chain giving functional non-structural proteins, are essential for viral replication and are medicinal chemistry targets. We report a high-throughput mass spectrometry (MS)-based assay which directly monitors PLpro catalysis in vitro. The assay was applied to investigate the effect of reported small-molecule PLpro inhibitors and selected Mpro inhibitors on PLpro catalysis. The results reveal that some, but not all, PLpro inhibitor potencies differ substantially from those obtained using fluorescence-based assays. Some substrate-competing Mpro inhibitors, notably PF-07321332 (nirmatrelvir) which is in clinical development, do not inhibit PLpro . Less selective Mpro inhibitors, e. g. auranofin, inhibit PLpro , highlighting the potential for dual PLpro /Mpro inhibition. MS-based PLpro assays, which are orthogonal to widely employed fluorescence-based assays, are of utility in validating inhibitor potencies, especially for inhibitors operating by non-covalent mechanisms.

The Importance of Flavonoids and Phytochemicals of Medicinal Plants with Antiviral Activities

In this mini-review article, we have mentioned the key roles of some of the most important herbal plants medicine containing flavonoids and phytochemicals with antiviral activities. All relevant information was searched by using the terms, influenza, phytochemicals, SARS, SARSCov-2, flavonoids, and traditional medicinal plants uses, from reliable databases, such as PubMed, Science Direct, and Google Scholar. The most important medicinal herbs which contain flavonoids with antiviral activities are Limonium densiflorum, Oroxylum indicum, Tribulus terrestris L., Paulownia tomentosa Steud., Allophylus africanus, Houttuynia cordata, Moslea Herba, Mosla scabra, Scutellaria baicalensis, Berries, Genus Psoralea, Sophora tonkinensis, Trollius chinensis, Tilia cordata, Hippophae rhamnoides L. (Seabuckthorn), Paulownia tomentosa steud, and C. swietenia. Phytochemicals are chemicals of plant origin produced by plants through primary or secondary metabolism. The most important medicinal plants, which contain phytochemicals with antiviral activities are chinensis, Sanguinaria Canadensis, Dodonaea viscosa, Isatis indigotica, Pelargonium sidoides, Entada Africana Guill., Pomegranate (Punica granatum), Goldenseal (Hydrastis canadensis), Lychee nium sanguineum L., and Tea polyphenols. Natural products from traditional herbal medicines, especially traditional Chinese and Persian medicines, have been found to exert antiviral impacts against influenza and human coronaviruses. The natural plant-derived compounds that have been used for treating various diseases are flavonoids and phytochemicals.

Role of Iron Chelation and Protease Inhibition of Natural Products on COVID-19 Infection.

Although the epidemic caused by SARS-CoV-2 callings for international attention to develop new effective therapeutics, no specific protocol is yet available, leaving patients to rely on general and supportive therapies. A range of respiratory diseases, including pulmonary fibrosis, have been associated with higher iron levels that may promote the course of viral infection. Recent studies have demonstrated that some natural components could act as the first barrier against viral injury by affecting iron metabolism. Moreover, a few recent studies have proposed the combination of protease inhibitors for therapeutic use against SARS-CoV-2 infection, highlighting the role of viral protease in virus infectivity. In this regard, this review focuses on the analysis, through literature and docking studies, of a number of natural products able to counteract SARS-CoV-2 infection, acting both as iron chelators and protease inhibitors.

Discovery of anti-infective adipostatins through bioactivity-guided isolation and heterologous expression of a type III polyketide synthase.

Antibiotic resistance and emerging viral pandemics have posed an urgent need for new anti-infective drugs. By screening our microbial extract library against the main protease of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the notorious ESKAPE pathogens, an active fraction was identified and purified, leading to an initial isolation of adipostatins A (1) and B (2). In order to diversify the chemical structures of adipostatins toward enhanced biological activities, a type III polyketide synthase was identified from the native producer, Streptomyces davawensis DSM101723, and was subsequently expressed in an E. coli host, resulting in the isolation of nine additional adipostatins 3-11, including two new analogs (9 and 11). The structures of 1-11 were established by HRMS, NMR, and chemical derivatization, including using a microgram-scale meta-chloroperoxybenzoic acid epoxidation-MS/MS analysis to unambiguously determine the double bond position in the alkyl chain. The present study discovered SARS-CoV-2 main protease inhibitory activity for the class of adipostatins for the first time. Several of the adipostatins isolated also exhibited antimicrobial activity against selected ESKAPE pathogens.