Primer for Designing Main Protease (Mpro) Inhibitors of SARS-CoV-2

The COVID-19 outbreak has been devastating, with hundreds of millions of infections and millions of deaths reported worldwide. In response, the application of structure-activity relationships (SAR) upon experimentally validated inhibitors of SARS-CoV-2 main protease (Mpro) may provide an avenue for the identification of new lead compounds active against COVID-19. Upon the basis of information gleaned from a combination of reported crystal structures and the docking of experimentally validated inhibitors, four "rules" for designing potent Mpro inhibitors have been proposed. The aim here is to guide medicinal chemists toward the most probable hits and to provide guidance on repurposing available structures as Mpro inhibitors. Experimental examination of our own previously reported inhibitors using the four "rules" identified a potential lead compound, the cathepsin inhibitor GB111-NH2, that was 2.3 times more potent than SARS-CoV-2 Mpro inhibitor N3.

Design and various in silico studies of the novel curcumin derivatives as potential candidates against COVID-19 -associated main enzymes

The novel coronavirus disease (COVID-19) is a highly contagious disease caused by the SARS-CoV-2 virus, leading severe acute respiratory syndrome in patients. Although various antiviral drugs and their combinations have been tried so far against SARS-CoV-2 and they have shown some effectiveness, there is still a need for safe and cost-effective binding inhibitors in the fight against COVID-19. Therefore, phytochemicals in nature can be a quick solution due to their wide therapeutic spectrum and strong antiviral, anti-inflammatory, and antioxidant properties. In this context, the low toxicity, and high pharmacokinetic properties of curcumin, which is a natural phytochemical, as well as the easy synthesizing of its derivatives reveal the need for investigation of its various derivatives as inhibitors against coronaviruses. The present study focused on curcumin derivatives with reliable ADME profile and high molecular binding potency to different SARS-CoV-2 target enzymes (3CLPro, PLpro, NSP7/8/12, NSP7/8/12 +RNA, NSP15, NSP16, Spike, Spike+ACE). In the molecular docking studies, the best binding scores for the 22 proposed curcumin derivatives were obtained for the PLpro protein. Furthermore, MD simulations were performed for high-affinity ligand-PLpro protein complexes and subsequently, Lys157, Glu161, Asp164, Arg166, Glu167, Met208, Pro247, Pro248, Tyr264, Tyr273 and Asp302 residues of PLpro was determined to play key role for ligand binding by Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) analysis. The results of the study promise that the proposed curcumin derivatives can be potent inhibitors against SARS-CoV-2 and be converted into pharmaceutical drugs. It is also expected that the findings may provide guiding insights to future design studies for synthesizing different antiviral derivatives of phytochemicals.

Determination of potential inhibitors based on isatin derivatives against SARS-CoV-2 main protease (mpro): a molecular docking, molecular dynamics and structure-activity relationship studies

SARS-COV-2, the novel coronavirus and root of global pandemic COVID-19 caused a severe health threat throughout the world. Lack of specific treatments raised an effort to find potential inhibitors for the viral proteins. The recently invented crystal structure of SARS-CoV-2 main protease (Mpro) and its key role in viral replication; non-resemblance to any human protease makes it a perfect target for inhibitor research. This article reports a computer-aided drug design (CADD) approach for the screening of 118 compounds with 16 distinct heterocyclic moieties in comparison with 5 natural products and 7 repurposed drugs. Molecular docking analysis against Mpro protein were performed finding isatin linked with a oxidiazoles (A2 and A4) derivatives to have the best docking scores of -11.22 kcal/mol and -11.15 kcal/mol respectively. Structure-activity relationship studies showed a good comparison with a known active Mpro inhibitor and repurposed drug ebselen with an IC50 value of -0.67 μM. Molecular Dynamics (MD) simulations for 50 ns were performed for A2 and A4 supporting the stability of the two compounds within the binding pocket, largely at the S1, S2 and S4 domains with high binding energy suggesting their suitability as potential inhibitors of Mpro for SARS-CoV-2.

Kobophenol A Inhibits Binding of Host ACE2 Receptor with Spike RBD Domain of SARS-CoV-2, a Lead Compound for Blocking COVID-19

In the search for inhibitors of COVID-19, we have targeted the interaction between the human angiotensin-converting enzyme 2 (ACE2) receptor and the spike receptor binding domain (S1-RBD) of SARS-CoV-2. Virtual screening of a library of natural compounds identified Kobophenol A as a potential inhibitor. Kobophenol A was then found to block the interaction between the ACE2 receptor and S1-RBD in vitro with an IC50 of 1.81 ± 0.04 μM and inhibit SARS-CoV-2 viral infection in cells with an EC50 of 71.6 μM. Blind docking calculations identified two potential binding sites, and molecular dynamics simulations predicted binding free energies of -19.0 ± 4.3 and -24.9 ± 6.9 kcal/mol for Kobophenol A to the spike/ACE2 interface and the ACE2 hydrophobic pocket, respectively. In summary, Kobophenol A, identified through docking studies, is the first compound that inhibits SARS-CoV-2 binding to cells through blocking S1-RBD to the host ACE2 receptor and thus may serve as a good lead compound against COVID-19.

Computational Studies of bis-2-Oxoindoline Succinohydrazides and their In Vitro Cytotoxicity

Background:

The discovery of clinically relevant EGFR inhibitors for cancer therapy has proven to be a challenging task. To identify novel and potent EGFR inhibitors, the quantitative structure-activity relationship (QSAR) and molecular docking approach became a very useful and largely widespread technique for drug design.

Methods:

We performed the in vitro cytotoxic activity on HEPG-2 cell line and earlier on MCF-7 and A 549 by using MTT assay method. The development of 3D QSAR model of N1,N4-bis(2-oxoindolin-3- ylidene) succinohydrazides using the stepwise-backward variable methods to generate Multiple Linear Regression method elucidates the structural properties required for EGFR inhibitory activity and also perform the Molecular Docking studies on EGFR (PDB ID:1M17). Further, we analysed for Lipinski’s rule of five to evaluate the drug-likeness and established in silico ADMET properties.

Results:

The resulting cytotoxicity (IC50) values ranged from 9.34 to 100 μM and compared with cisplatin as a standard. Among the series of compounds, 6j showed good cytotoxic activity on HEPG-2 cell line with 9.34 μM, IC50 value. Most of the evaluated compounds showed good antitumor activity on HEPG-2 than MCF-7and A549. The developed 3D QSAR Multiple Linear Regression models are statistically significant with non-cross-validated correlation coefficient r2 = 0.9977, cross-validated correlation coefficient q2 = 0.902 and predicted_r2 = 0.9205. Molecular docking studies on EGFR (PDB ID: 1M17) results, compounds 6d, 6j and 6l showed good dock/PLP scores i.e. -81.28, -73.98 and -75.37, respectively, by interacting with Leu-694, Val-702 and Gly-772 amino acids via hydrophobic and hydrogen bonds with Asn818 and Met- 769. Further, we analysed drug-likeness and established in silico ADMET properties.

Conclusion:

The results of 3D QSAR studies suggest that the electrostatic and steric descriptors influence the cytotoxic activity of succinohydrazides. From the molecular docking studies, it is evident that hydrophobic, hydrogen and Van Der Waal’s interactions determine binding affinities. In addition to this, druglikeness and ADMET properties were analysed. It is evident that there is a correlation between the QSAR and docking results. Compound 6j was found to be too lipophilic due to its dihalo substitution on isatin nucleus, and can act as a lead molecule for further and useful future development of new EGFR Inhibitors.

Monoamine oxidase-B inhibitors as potential neurotherapeutic agents: An overview and update

Monoamine oxidase (MAO) inhibitors have made significant contributions and remain an indispensable approach of molecular and mechanistic diversity for the discovery of antineurodegenerative drugs. However, their usage has been hampered by nonselective and/or irreversible action which resulted in drawbacks like liver toxicity, cheese effect, and so forth. Hence, the search for selective MAO inhibitors (MAOIs) has become a substantial focus in current drug discovery. This review summarizes our current understanding on MAO-A/MAO-B including their structure, catalytic mechanism, and biological functions with emphases on the role of MAO-B as a potential therapeutic target for the development of medications treating neurodegenerative disorders. It also highlights the recent developments in the discovery of potential MAO-B inhibitors (MAO-BIs) belonging to diverse chemical scaffolds, arising from intensive chemical-mechanistic and computational studies documented during past 3 years (2015-2018), with emphases on their potency and selectivity. Importantly, readers will gain knowledge of various newly established MAO-BI scaffolds and their development potentials. The comprehensive information provided herein will hopefully accelerate ideas for designing novel selective MAO-BIs with superior activity profiles and critical discussions will inflict more caution in the decision-making process in the MAOIs discovery.

Novel halogenated pyrido[2,3-a]carbazoles with enhanced aromaticity as potent anticancer and antioxidant agents: rational design and microwave assisted synthesis

Design and synthesis a series of pyrido[2,3-a]carbazoles for their anticancer and antioxidant activity.

Curcumin-based pyrazoline analogues as selective inhibitors of human monoamine oxidase A

A series of 2-methoxy-4-(5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)phenol (pyrazoline) derivatives (2-6) have been synthesized and tested for human monoamine oxidase (hMAO) inhibitory activity. The most active derivative (2) behaved as a competitive hMAO-A inhibitor, with an inhibition constant value of 0.08 μM and a strong hMAO-A selectivity (K_i(hMAO-B)/K_i(hMAO-A) > 1751). In addition, 2 exhibited little to no cytotoxic effects up to a 25 μM concentration and provided the best blood-brain barrier permeability among the derivatives synthesized. Molecular dynamics simulations revealed that a chlorine substituent at the para-position of the phenyl ring in 2 enabled a π-π stacking interaction with Tyr407 and Tyr444 that resulted in the formation of an "aromatic sandwich" structure. Consequently, this tight-binding aromatic cage culminated in a dramatically reduced active site volume that is believed to be the origin of the observed selectivity between the hMAO-A and hMAO-B isozymes. Removal of the chlorine from 2 disrupted the favorable intermolecular interactions and resulted in a selectivity change towards hMAO-B.