Computational Analysis of Molnupiravir

Multi-spectroscopic, calorimetric and molecular dynamics evaluation on non-classical intercalation of antiviral drug Molnupiravir with DNA

The interaction of an antiviral drug Molnupiravir (MOL) with calf thymus DNA (CT-DNA) was investigated using a series of biophysical techniques. A significant hyperchromism with a blue shift  nm in the UV-Vis spectra indicated a high binding affinity of MOL for CT-DNA with binding constants in the order of 105 M-1. Competitive fluorescent dye displacement assays with ethidium bromide (EB) and Hoechst 33258 suggested an intercalative mode of binding of MOL with CT-DNA. Thermodynamic profiles determined using fluorescence titration and isothermal titration calorimetric (ITC) analysis matched well with each other. The negative free energy change revealed that the MOL/CT-DNA complexation is a spontaneous process. The negative values of enthalpy and entropy changes indicated that H-bonding and van der Walls interactions play dominant roles in stabilizing the complex. A decrease in viscosity of CT-DNA solution upon adding MOL indicated a partial intercalation mode of binding which was well supported by circular dichroism (CD) spectral and effect of KI and denaturation studies. Molecular docking and metadynamics simulation studies clearly showed the partial intercalation of the pyrimidine ring of MOL into the base pairs of DNA. Free energy surface (FES) contour indicated that the drug/DNA complex is stabilized by H-bonding and pi-pi/pi-cation interactions.Communicated by Ramaswamy H. Sarma.

A comparative study of electropolymerization and photopolymerization for the determination of molnupiravir and their application in an electrochemical sensor via computationally designed molecularly imprinted polymers

A comparative analysis of molecularly imprinted polymers based on different synthesis techniques was performed for the recognition of molnupiravir (MOL). The polymerizations were performed with 3-thienyl boronic acid (3-TBA) as a functional monomer by electropolymerization (EP) and with guanine methacrylate (GuaM) as a functional monomer by photopolymerization (PP). Morphological and electrochemical characterizations of the developed sensors were investigated to verify the constructed sensors. Moreover, quantum chemical calculations were used to evaluate changes on the electrode surface at the molecular and electronic levels. The dynamic linear range of both designed sensors under optimized experimental conditions was found to be 7.5 × 10-12-2.5 × 10-10 M and 7.5 × 10-13-2.5 × 10-11 M for EP and PP, respectively. The effect of various interfering agents on MOL peak current was assessed for the selectivity of the study. In the presence of 100 times more interfering agents, the RSD and recovery values were determined. The RSD values of GuaM/MOL@MIP/GCE and poly(Py-co-3-PBA)/MOL@MIP/GCE sensors were found to be 1.99% and 1.72%, respectively. Furthermore, the recovery values of the MIP-based sensors were 98.18-102.69% and 98.05-103.72%, respectively. In addition, the relative selectivity coefficient (k') of the proposed sensor was evaluated, and it exhibited good selectivity for MOL with respect to the NIP sensor. The prepared sensor was successfully applied to determine MOL in commercial serum samples and capsule form. In conclusion, the developed sensors provided excellent reproducibility, repeatability, high sensitivity, and selectivity against the MOL molecule.

Thermodynamic and Kinetic Characteristics of Molnupiravir Tautomers and Its Complexes with RNA Purine Bases as an Explanation of the Possible Mechanism of Action of This Novel Antiviral Medicine: A Quantum-Chemical Study

The mechanism of action of molnupiravir, a novel antiviral drug, was analyzed from the point of view of its tautomerism by means of quantum-mechanical calculations. It was established that although the uracil-like tautomer Mu (3 kcal/mol in the water environment) is the most thermodynamically stable, in fact, it is the cytosine-like tautomer Mc that plays the main role. There are several reasons, as follows: (1) A large part of Mu exists as a more stable but inactive form Mu-m that is unable to pair with adenine. (2) The phosphorylated form of Mc is only 1 kcal/mol less stable than Mu in the water environment and thus is readily available for building into the RNA strand, where the Mu/Mc energy gap increases and the probability of Mc → Mu interconversion leading to C → U mutation is high. (3) The guanine-Mc complex has similar stability to guanine-cytosine, but the adenine-Mu complex has lower stability than adenine-uracil. Additionally, the guanine-Mc complex has a suboptimal distorted geometry that further facilitates the mutations. (4) The activation barrier for proton transfer leading to Mu-m interconversion into a cytosine-like tautomer is higher than for Mu, which makes the uracil-like form even less available. These facts confirm an intriguing experimental observation that molnupiravir competes mainly with cytosine and not uracil.

Preferability of Molnupiravir, an Anti-COVID-19 Drug, toward Purine Nucleosides: A Quantum Mechanical Study

Structural aspects of molnupiravir complexed with the RNA of the SARS-CoV-2 virus have been recently resolved inside the RNA-dependent RNA polymerase (RdRp), demonstrating the interactions of molnupiravir with purine nucleosides. However, the preference of molnupiravir to interact with one purine nucleoside over another has not been clearly investigated. Herein, the complexation of molnupiravir in its active form with guanosine and adenosine was compared, using sundry density functional theory calculations. The plausible tautomeric structures of the molnupiravir drug in complex with guanosine/adenosine were minutely scrutinized. The relative energy findings outlined the favorability of amino-molnupiravir···keto-amino-guanosine and imino-molnupiravir···amino-adenosine optimized complexes. According to the interaction (Eint) and binding (Ebind) energy values, higher preferential base-pairing of molnupiravir with guanosine over the adenosine one was recognized with Eint/Ebind values of -31.16/-21.81 and -13.93/-12.83 kcal/mol, respectively. This could be interpreted by the presence of three and two hydrogen bonds within the former and latter complexes, respectively. Observable changes in the electronic properties and global indices of reactivity of the studied complexes also confirmed the preferential binding within the studied complexes. The findings from the quantum theory of atoms in molecules and the noncovalent interaction index also support the partially covalent nature of the investigated interactions. For both complexes, changes in thermodynamic parameters outlined the spontaneous, exothermic, and nonrandom states of the inspected interactions. Inspecting the solvent effect on the studied interactions outlined more observable amelioration within the water medium compared with the gas one. These results would be a durable ground for the forthcoming studies concerned with the interactions of the molnupiravir drug with purine nucleosides.

Chiral discrimination of cyclodecapeptide to anti-COVID-19 clinical candidates: a theoretical study

Various undesirable side effects are frequently associated with isomers of chiral clinical agents. The separation of chiral medicines remains a challenging issue in the medicines research. In this work, we employed cyclic decapeptide as the host molecule and the M06-2X theoretical computational method for chiral recognition of four clinical candidate guests and their isomers, including bucillamine, molnupiravir, azvudine, and VV116, which are relevant for the treatment of COVID-19. The obtained results indicated that bucillamine and molnupiravir and their respective isomers may be distinguished by cyclic decapeptide and that some of the isomers of Azvudine and VV116 may be discriminated by cyclic decapeptide. The inclusion conformation, deformation analysis, and electrostatic potential analysis also visualized the binding modes and binding sites between cyclic peptides and medicine candidates. A series of weak interaction analyses suggest that hydrogen bonding and dispersion interactions may be the primary factors for the recognition and separation of the clinical candidates by cyclic decapeptides. Visualized analyses of noncovalent interaction, hydrogen bond interaction, and NBO, AIM topological demonstrated that the difference of dispersion interaction is not obvious between the complexes, while the type and number of hydrogen bonds are very different, hinting that hydrogen bonds might be crucial for the differentiation of molnupiravir and its isomers. These findings might provide a theoretical reference for the identification and separation of chiral compounds in host-guest interaction.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11224-023-02149-5.

A Novel Ambroxol-Derived Tetrahydroquinazoline with a Potency against SARS-CoV-2 Proteins

We report synthesis of a novel 1,2,3,4-tetrahydroquinazoline derivative, named 2-(6,8-dibromo-3-(4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazolin-2-yl)phenol (1), which was obtained from the hydrochloride of 4-((2-amino-3,5-dibromobenzyl)amino)cyclohexan-1-ol (ambroxol hydrochloride) and salicylaldehyde in EtOH. The resulting compound was produced in the form of colorless crystals of the composition 1∙0.5EtOH. The formation of the single product was confirmed by the IR and 1H spectroscopy, single-crystal and powder X-ray diffraction, and elemental analysis. The molecule of 1 contains a chiral tertiary carbon of the 1,2,3,4-tetrahydropyrimidine fragment and the crystal structure of 1∙0.5EtOH is a racemate. Optical properties of 1∙0.5EtOH were revealed by UV-vis spectroscopy in MeOH and it was established that the compound absorbs exclusively in the UV region up to about 350 nm. 1∙0.5EtOH in MeOH exhibits dual emission and the emission spectra contains bands at about 340 and 446 nm upon excitation at 300 and 360 nm, respectively. The DFT calculations were performed to verify the structure as well as electronic and optical properties of 1. ADMET properties of the R-isomer of 1 were evaluated using the SwissADME, BOILED-Egg, and ProTox-II tools. As evidenced from the blue dot position in the BOILED-Egg plot, both human blood-brain barrier penetration and gastrointestinal absorption properties are positive with the positive PGP effect on the molecule. Molecular docking was applied to examine the influence of the structures of both R-isomer and S-isomer of 1 on a series of the SARS-CoV-2 proteins. According to the docking analysis results, both isomers of 1 were found to be active against all the applied SARS-CoV-2 proteins with the best binding affinities with Papain-like protease (PLpro) and nonstructural protein 3 (Nsp3_range 207-379-AMP). Ligand efficiency scores for both isomers of 1 inside the binding sites of the applied proteins were also revealed and compared with the initial ligands. Molecular dynamics simulations were also applied to evaluate the stability of complexes of both isomers with Papain-like protease (PLpro) and nonstructural protein 3 (Nsp3_range 207-379-AMP). The complex of the S-isomer with Papain-like protease (PLpro) was found to be highly unstable, while the other complexes are stable.

Molnupiravir: A Versatile Prodrug against SARS-CoV-2 Variants

The nucleoside analog β-D-N4-hydroxycytidine is the active metabolite of the prodrug molnupiravir and is accepted as an efficient drug against COVID-19. Molnupiravir targets the RNA-dependent RNA polymerase (RdRp) enzyme, which is responsible for replicating the viral genome during the replication process of certain types of viruses. It works by disrupting the normal function of the RdRp enzyme, causing it to make mistakes during the replication of the viral genome. These mistakes can prevent the viral RNA from being transcribed, converted into a complementary DNA template, translated, or converted into a functional protein. By disrupting these crucial steps in the viral replication process, molnupiravir can effectively inhibit the replication of the virus and reduce its ability to cause disease. This review article sheds light on the impact of molnupiravir and its metabolite on SARS-CoV-2 variants of concern, such as delta, omicron, and hybrid/recombinant variants. The detailed mechanism and molecular interactions using molecular docking and dynamics have also been covered. The safety and tolerability of molnupiravir in patients with comorbidities have also been emphasized.

Copper(II) Chelates of Schiff Bases Enriched with Aliphatic Fragments: Synthesis, Crystal Structure, In Silico Studies of ADMET Properties and a Potency against a Series of SARS-CoV-2 Proteins

We report two complexes [Cu(LI)2] (1) and [Cu(LII)2] (2) (HLI = N-cyclohexyl-3-methoxysalicylideneimine, HLII = N-cyclohexyl-3-ethoxysalicylideneimine). The ligands in both complexes are trans-1,5-N,O-coordinated, yielding a square planar CuN2O2 coordination core. The molecule of 1 is planar with two cyclohexyl groups oriented to the opposite sites of the planar part of a molecule, while the molecule of 2 is significantly bent with two cyclohexyl groups oriented to the same convex site of a molecule. It was established that both complexes in MeOH absorb in the UV region due to intraligand transitions and LMCT. Furthermore, the UV-vis spectra of both complexes revealed two low intense shoulders in the visible region at about 460 and 520 nm, which were attributed to d-d transitions. Both complexes were predicted to belong to a fourth class of toxicity with the negative BBB property and positive gastrointestinal absorption property. According to the molecular docking analysis results, both complexes are active against all the applied SARS-CoV-2 proteins with the best binding affinity with Nsp 14 (N7-MTase), PLpro and Mpro. The obtained docking scores of complexes are either comparable to or even higher than those of the initial ligands. Complex 1 was found to be more efficient upon interaction with the applied proteins in comparison to complex 2. Ligand efficiency scores for the initial ligands, 1 and 2 were also revealed.

A novel coumarin-triazole-thiophene hybrid: synthesis, characterization, ADMET prediction, molecular docking and molecular dynamics studies with a series of SARS-CoV-2 proteins

Synthesis, characterization and theoretical studies of a novel coumarin-triazole-thiophene hybrid 4-(((4-ethyl-5-(thiophen-2-yl)-4H-1,2,4-triazol-3-yl)thio)methyl)-6,7-dimethyl-2H-chromen-2-one (1), which was fabricated from 4-ethyl-5-(thiophen-2-yl)-4H-1,2,4-triazole-3-thiol and 4-(chloromethyl)-6,7-dimethyl-2H-chromen-2-one, are reported. The resulting compound was characterized by microanalysis, IR, 1H, and 13C APT NMR spectroscopy. The DFT calculations examined the structure and electronic properties of 1 in gas phase. Its reactivity descriptors and molecular electrostatic potential revealed the reactivity and the reactive centers of 1. ADMET properties of 1 were evaluated using the respective online tools. It was established that 1 exhibit positive gastrointestinal absorption properties and negative human blood-brain barrier penetration. The Toxicity Model Report revealed that 1 belongs to toxicity class 4. Molecular docking was additionally applied to study the interaction of 1 with some SARS-CoV-2 proteins. It was established that the title compound is active against all the applied proteins with the most efficient interaction with Papain-like protease (PLpro). The interaction of 1 with the applied proteins was also studied using molecular dynamics simulations.

Graphical abstract

A novel coumarin-triazole-thiophene hybrid 4-(((4-ethyl-5-(thiophen-2-yl)-4H-1,2,4-triazol-3-yl)thio)methyl)-6,7-dimethyl-2H-chromen-2-one (1) is reported. The structure and electronic properties of 1 were examined by the DFT calculations. ADMET properties of 1 were also evaluated. Molecular docking and molecular dynamics simulations were applied to study interactions of 1 with a series of the SARS-CoV-2 proteins.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12039-022-02127-0.

In Vitro and In Silico Studies for the Identification of Potent Metabolites of Some High-Altitude Medicinal Plants from Nepal Inhibiting SARS-CoV-2 Spike Protein

Despite ongoing vaccination programs against COVID-19 around the world, cases of infection are still rising with new variants. This infers that an effective antiviral drug against COVID-19 is crucial along with vaccinations to decrease cases. A potential target of such antivirals could be the membrane components of the causative pathogen, SARS-CoV-2, for instance spike (S) protein. In our research, we have deployed in vitro screening of crude extracts of seven ethnomedicinal plants against the spike receptor-binding domain (S1-RBD) of SARS-CoV-2 using an enzyme-linked immunosorbent assay (ELISA). Following encouraging in vitro results for Tinospora cordifolia, in silico studies were conducted for the 14 reported antiviral secondary metabolites isolated from T. cordifolia-a species widely cultivated and used as an antiviral drug in the Himalayan country of Nepal-using Genetic Optimization for Ligand Docking (GOLD), Molecular Operating Environment (MOE), and BIOVIA Discovery Studio. The molecular docking and binding energy study revealed that cordifolioside-A had a higher binding affinity and was the most effective in binding to the competitive site of the spike protein. Molecular dynamics (MD) simulation studies using GROMACS 5.4.1 further assayed the interaction between the potent compound and binding sites of the spike protein. It revealed that cordifolioside-A demonstrated better binding affinity and stability, and resulted in a conformational change in S1-RBD, hence hindering the activities of the protein. In addition, ADMET analysis of the secondary metabolites from T. cordifolia revealed promising pharmacokinetic properties. Our study thus recommends that certain secondary metabolites of T. cordifolia are possible medicinal candidates against SARS-CoV-2.

Drugs for COVID-19: An Update

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the seventh known human coronavirus, and it was identified in Wuhan, Hubei province, China, in 2020. It caused the highly contagious disease called coronavirus disease 2019 (COVID-19), declared a global pandemic by the World Health Organization (WHO) on 11 March 2020. A great number of studies in the search of new therapies and vaccines have been carried out in these three long years, producing a series of successes; however, the need for more effective vaccines, therapies and other solutions is still being pursued. This review represents a tracking shot of the current pharmacological therapies used for the treatment of COVID-19.

In silico analyses of betulin: DFT studies, corrosion inhibition properties, ADMET prediction, and molecular docking with a series of SARS-CoV-2 and monkeypox proteins

We report detailed computational studies of betulin - a pentacyclic naturally occuring triterpene, which is a precursor for a broad family of biologically active derivatives. The structure, electronic, and optical properties of betulin were studied by the density functional theory (DFT) calculations in gas phase. The reactivity and the reactive centers of betulin were revealed through its global reactivity descriptors and molecular electrostatic potential (MEP). The DFT calculations were also applied to probe betulin as a potential corrosion inhibitor for some important metals used in implants. Electron charge transfer from the molecule of betulin to the surface of all the examined metals (Ti, Fe, Zr, Co, Cu, Cr, Ni, Mn, Mo, Zn, Al, W, Ag, Au) was revealed, of which the best results were obtained for Ni, Au and Co. Bioavailability, druggability as well as absorption, distribution, metabolism, excretion and toxicity (ADMET) properties of betulin were evaluated using the SwissADME, BOILED-Egg and ProTox-II tools. Molecular docking was applied to examine the influence of the title compound on a series of the SARS-CoV-2 proteins as well as one of the monkeypox proteins. It was established that betulin is active against all the applied proteins with the best binding affinity with papain-like protease (PLpro) and spike protein (native) of SARS-CoV-2. The title compound is also active against the studied monkeypox protein. Interaction of betulin with papain-like protease (PLpro) was studied using molecular dynamics simulations.

Correction: Sharov et al. Computational Analysis of Molnupiravir. Int. J. Mol. Sci. 2022, 23, 1508

We received a complaint from the Université Catholique de Louvain [...].

Fullerene Derivatives for Drug Delivery against COVID-19: A Molecular Dynamics Investigation of Dendro[60]fullerene as Nanocarrier of Molnupiravir

In this paper, a theoretical investigation is made regarding the possibility of using a water-soluble derivative of C₆₀ as a drug delivery agent for treating Coronavirus disease 2019 (COVID-19). Molnupiravir is chosen as the transporting pharmaceutical compound since it has already proved to be very helpful in saving lives in case of hospitalization. According to the proposed formulation, a carboxyfullerene known as dendro[60]fullerene is externally connected with two molnupiravir molecules. Two properly formed nitrogen single bonds (N-N) are used as linkers between the dendro[60]fullerene and the two molnupiravir molecules to create the final form of the C₆₀ derivate/molnupiravir conjugate. The energetics of the developed molecular system and its interaction with water and n-octanol are extensively studied via classical molecular dynamics (MD) using the COMPASS II force field. To study the interactions with water and n-octanol, an appropriate periodic amorphous unit cell is created that contains a single C₆₀ derivative/molnupiravir system surrounded by numerous solvent molecules and simulated via MD in room conditions. In addition, the corresponding solvation-free energies of the investigated drug delivery system are computed and set in contrast with the corresponding properties of the water-soluble dendro[60]fullerene, to test its solubility capabilities.

The effect of various compounds on the COVID mechanisms, from chemical to molecular aspects

The novel coronavirus that caused COVID-19 pandemic is SARS-CoV-2. Although various vaccines are currently being used to prevent the disease's severe consequences, there is still a need for medications for those who become infected. The SARS-CoV-2 has a variety of proteins that have been studied extensively since the virus's advent. In this review article, we looked at chemical to molecular aspects of the various structures studied that have pharmaceutical activity and attempted to find a link between drug activity and compound structure. For example, designing of the compounds which bind to the allosteric site and modify hydrogen bonds or the salt bridges can disrupt SARS-CoV2 RBD–ACE2 complex. It seems that quaternary ammonium moiety and quinolin-1-ium structure could act as a negative allosteric modulator to reduce the tendency between spike-ACE2. Pharmaceutical structures with amino heads and hydrophobic tails can block envelope protein to prevent making mature SARS-CoV-2. Also, structures based on naphthalene pharmacophores or isosteres can form a strong bond with the PLpro and form a π-π and the Mpro's active site can be occupied by octapeptide compounds or linear compounds with a similar fitting ability to octapeptide compounds. And for protein RdRp, it is critical to consider pH and pKa so that pKa regulation of compounds to comply with patients is very effective, thus, the presence of tetrazole, phenylpyrazole groups, and analogs of pyrophosphate in the designed drugs increase the likelihood of the RdRp active site inhibition. Finally, it can be deduced that designing hybrid drug molecules along with considering the aforementioned characteristics would be a suitable approach for developing medicines in order to accurate targeting and complete inhibition this virus.