In silico binding mechanism prediction of benzimidazole based corticotropin releasing factor-1 receptor antagonists by quantitative structure activity relationship, molecular docking and pharmacokinetic parameters calculation

Purification of ursolic acid and β-sitosterol from endophytic Alternaria alternata for their alpha-amylase inhibitory activity

Fungal endophytes are a known warehouse of bioactive compounds with multifarious applications. In the present investigation two compounds, β-Sitosterol (1) and ursolic acid (2), were isolated from Alternaria alternata, an endophytic fungus associated with Morus alba Linn for the first time. The structure of the compounds was elucidated on the basis of comprehensive spectral analysis (UV, IR, 1 H-, 13 C- and 2D-NMR, as well as HRESI-MS). In the in vitro alpha amylase inhibitory assay both compounds (1) and (2) show potent antidiabetic activity. In support, Docking studies indicate significant binding affinity of the isolated compounds. Hence from the present study, it can be concluded that endophytic fungi in Morus alba Linn can find use in antidiabetic drug development in the medicinal industry.Communicated by Ramaswamy H. Sarma.

Identification of potential inhibitors of Zika virus targeting NS3 helicase using molecular dynamics simulations and DFT studies

Despite the various research efforts towards the drug discovery program for Zika virus treatment, no antiviral drugs or vaccines have yet been discovered. The spread of the mosquito vector and ZIKV infection exposure is expected to accelerate globally due to continuing global travel. The NS3-Hel is a non-structural protein part and involved in different functions such as polyprotein processing, genome replication, etc. It makes an NS3-Hel protein an attractive target for designing novel drugs for ZIKV treatment. This investigation identifies the novel, potent ZIKV inhibitors by virtual screening and elucidates the binding pattern using molecular docking and molecular dynamics simulation studies. The molecular dynamics simulation results indicate dynamic stability between protein and ligand complexes, and the structures keep significantly unchanged at the binding site during the simulation period. All inhibitors found within the acceptable range having drug-likeness properties. The synthetic feasibility score suggests that all screened inhibitors can be easily synthesizable. Therefore, possible inhibitors obtained from this study can be considered a potential inhibitor for NS3 Hel, and further, it could be provided as a lead for drug development.

Structure prediction, molecular simulations of RmlD from Mycobacterium tuberculosis, and interaction studies of Rhodanine derivatives for anti-tuberculosis activity

Tuberculosis is the most dangerous disease causing maximum deaths than any other, caused by single infectious agent. Due to multidrug resistant of Mycobacterium tuberculosis strains, there is a need of new drugs and drug targets. In this work, we have selected RmlD (α-dTDP-6-deoxy-lyxo-4-hexulose reductase) in the dTDP Rhamnose pathway as drug target to control tuberculosis using Rhodanine analogues. In order to study interaction of RmlD with Rhodanine analogues, a three-dimensional model based on crystal structures such as 1VLO from Clostridium, 1KBZ from Salmonella typhimurium, and 2GGS from Sulfolobus was generated using Modeller 9v7. The modeled structure reliability has been checked using programs such as Procheck, What if, Prosa, Verify 3D, and Errat. In an attempt to find new inhibitors for RmlD enzyme, docking studies were done with a series of Rhodanine and its analogues. Detailed analysis of enzyme-inhibitor interactions identified specific key residues, SER5, VAL9, ILE51, HIS54, and GLY55 which were important in forming hydrogen bonds in binding affinity. Homology modeling and docking studies on RmlD model provided valuable insight information for designing better inhibitors as novel anti-tuberculosis drugs by rational method.

Is highly expressed ACE 2 in pregnant women "a curse" in times of COVID-19 pandemic?

Angiotensin-converting enzyme 2 (ACE 2) is a membrane-bound enzyme that cleaves angiotensin II (Ang II) into angiotensin (1-7). It also serves as an important binding site for SARS-CoV-2, thereby, facilitating viral entry into target host cells. ACE 2 is abundantly present in the intestine, kidney, heart, lungs, and fetal tissues. Fetal ACE 2 is involved in myocardium growth, lungs and brain development. ACE 2 is highly expressed in pregnant women to compensate preeclampsia by modulating angiotensin (1-7) which binds to the Mas receptor, having vasodilator action and maintain fluid homeostasis. There are reports available on Zika, H1N1 and SARS-CoV where these viruses have shown to produce fetal defects but very little is known about SARS-CoV-2 involvement in pregnancy, but it might have the potential to interact with fetal ACE 2 and enhance COVID-19 transmission to the fetus, leading to fetal morbidity and mortality. This review sheds light on a path of SARS-CoV-2 transmission risk in pregnancy and its possible link with fetal ACE 2.

Computational investigation of potential inhibitors of novel coronavirus 2019 through structure-based virtual screening, molecular dynamics and density functional theory studies

Despite the intensive research efforts towards antiviral drug against COVID-19, no potential drug or vaccines has not yet discovered. Initially, the binding site of COVID-19 main protease was predicted which located between regions 2 and 3. Structure-based virtual screening was performed through a hierarchal mode of elimination technique after generating a grid box. This led to the identification of five top hit molecules that were selected on the basis of docking score and visualization of non-bonding interactions. The docking results revealed that the hydrogen bonding and hydrophobic interactions are the major contributing factors in the stabilization of complexes. The docking scores were found between −7.524 and −6.711 kcal/mol indicating strong ligand-protein interactions. Amino acid residues Phe140, Leu141, Gly143, Asn142, Thr26, Glu166 and Thr190 (hydrogen bonding interactions) and Phe140, Cys145, Cys44, Met49, Leu167, Pro168, Met165, Val42, Leu27 and Ala191 (hydrophobic interactions) formed the binding pocket of COVID-19 main protease. From identified hits, ZINC13144609 and ZINC01581128 were selected for atomistic MD simulation and density functional theory calculations. MD simulation results confirm that the protein interacting with both hit molecules is stabilized in the chosen POPC lipid bilayer membrane. The presence of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) in the hydrophobic region of the hit molecules leads to favorable ligand-protein contacts. The calculated pharmacokinetic descriptors were found to be in their acceptable range and therefore confirming their drug-like properties. Hence, the present investigation can serve as the basis for designing and developing COVID-19 inhibitors.

Communicated by Ramaswamy H. Sarma

In Silico Studies on Anti-Stress Compounds of Ethanolic Root Extract of Hemidesmus indicus L

BACKGROUND

Alternative medicine is available for those diseases which cannot be treated by conventional medicine. Ayurveda and herbal medicines are important alternative methods in which the treatment is done with extracts of different medicinal plants. This work is concerned with the evaluation of anti-stress bioactive compounds from the ethanolic root extract of Hemidesmus indicus.

METHODS

Gas chromatography and Mass Spectrum studies are used to identify the compounds present in the ethanolic extract based on the retention time, area. In order to perform docking studies, Vasopressin model is generated using modeling by Modeller 9v7. Vasopressin structure is developed based on the crystal structure of neurophysin-oxytocin from Bos taurus (PDB ID: 1NPO_A) collected from the PDB data bank. Using molecular dynamics simulation methods, the final predicted structure is obtained and further analyzed by verifying 3D and PROCHECK programs, confirmed that the final model is reliable. The identified compounds are docked to vasopressin for the prediction of anti-stress activity using GOLD 3.0.1 software.

RESULTS

The predicted model of Vasopressin structure is stabilized and confirmed that it is a reliable structure for docking studies. The results indicated ARG4, THR7, ASP9, ASP26, ALA32, ALA 80 in Vasopressin are important determinant residues in binding as they have strong hydrogen bonding with phytocompounds. Among the 21 phytocompounds identified and docked, molecule Deoxiinositol, pentakis- O-(trimethylsilyl) showed the best docking results with Vasopressin.

CONCLUSION

The identified compounds were used for anti-stress activity by insilico method with Vasopressin which plays an important role in causing stress and hence selected for inhibitory studies with phytocompounds. The phytocompounds are inhibiting vasopressin through hydrogen bodings and are important in protein-ligand interactions. Docking results showed that out of twenty-one compounds, Deoxiinositol, pentakis-O-(trimethylsilyl) showed best docking energy to the Vasopressin.

Synthesis, characterization and biological evaluation of novel benzimidazole derivatives

In search of achieving less toxic and more potent chemotherapeutics, three novel heterocyclic benzimidazole derivatives: 2-(1H-benzo[d]imidazol-2-yl)-4-chlorophenol (BM1), 4-chloro-2-(6-methyl-1H-benzo[d]imidazol-2-yl)phenol (BM2) and 4-chloro-2-(6-nitro-1H-benzo[d]imidazol-2-yl)phenol (BM3) with DNA-targeting properties, were synthesized and fully characterized by important physicochemical techniques. The DNA binding properties of the compounds were investigated by UV-Visible absorption titrations and thermal denaturation experiments. These molecules exhibited a good binding propensity to fish sperm DNA (FS-DNA), as evident from the high binding constants (K_b) values: 1.9 × 10⁵, 1.39 × 10⁵ and 1.8 × 10⁴ M^‒1 for BM1, BM2 and BM3, respectively. Thermal melting studies of DNA further validated the absorption titration results and best interaction was manifested by BM1 with ΔT_m = 4.96 °C. The experimental DNA binding results were further validated theoretically by molecular docking study. It was confirmed that the molecules (BM1-BM3) bind to DNA via an intercalative and groove binding mode. The investigations showed a correlation between binding constants and energies obtained experimentally and through molecular docking, indicating a binding preference of benzimidazole derivatives with the minor groove of DNA. BM1 was the preferential candidate for DNA binding because of its flat structure, π-π interactions and less steric hindrance. To complement the DNA interaction, antimicrobial assays (antibacterial & antifungal) were performed. It was observed that compound BM2 showed promising activity against all bacterial strains (Micrococcus luteus, Staphylococcus aureus, Enterobacter aerogenes and Escherichia coli) and fungi (Aspergillus flavus, Aspergillus fumigatus and Fusarium solani), while rest of the compounds were active against selective strains. The MIC values of BM2 were found to be in the range of 12.5 ± 2.2-25 ± 1.5 µg/mL. Thus, the compound BM2 was found to be the effective DNA binding antimicrobial agent. Furthermore, the preliminary cytotoxic properties of synthesized compounds were evaluated by brine shrimps lethality assay to check their nontoxic nature towards healthy normal cells.Communicated by Ramaswamy H. Sarma.

Synthesis and characterization of heterobimetallic SnIV-CuII/ZnII complexes: DFT studies, cleavage potential and cytotoxic activity

Heterobimetallic complexes [Cu(L)Sn(CH₃)₂(H₂O)(Cl)] (3) and [Zn(L)Sn(CH₃)₂(H₂O)(Cl)] (4) have been synthesized from their monometallic analogs [Cu(L)(H₂O)(Cl)] (1) and [Zn(L)(H₂O)(Cl)] (2) of Schiff base ligand (L) which were characterized by various spectroscopic and analytical methods. DFT calculations were carried out to simulate the vibrational spectra to support the anticipated structures. The interaction studies of ligand (L) and complexes (1-4) with CT-DNA were performed by employing UV-vis, and fluorescence spectroscopic techniques which revealed that heterobimetallic complexes 3 and 4 showed higher affinity with DNA due to dual mode of action as compared to monometallic complexes 1 and 2. Further, validation of the interaction studies was accomplished by carrying out molecular docking studies with DNA. Gel assay displayed that both the complexes have ability to cleave DNA efficiently and are specific minor groove binders. Cu^II-Sn^IV complex 3 cleaved pBR322 DNA via oxidative mechanism, while Zn^II-Sn^IV complex 4 followed hydrolytic cleavage pathway. In vitro cytotoxicity evaluation of complex 3 was tested on a different cancer cell lines showing promising antitumor activity.Communicated by Ramaswamy H. Sarma.

Combined 3D-QSAR, molecular docking and molecular dynamics study on the benzimidazole inhibitors targeting HCV NS5B polymerase

The hepatitis C virus (HCV)-infected population has continued to grow during recent years, and novel HCV antiviral agents are urgently needed. In this work, a combined theoretical study was performed on the HCV non-structural 5B (NS5B) polymerase and 53 benzimidazole inhibitors. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were carried out with ligand-based and receptor-based alignments. Ligand-based QSAR models (cross-validated q² of 0.918 for CoMFA and 0.825 for CoMSIA) were found to be superior to receptor-based approaches (cross-validated q² of 0.765 for CoMFA and 0.740 for CoMSIA). Based on the most predictive CoMFA and CoMSIA models, the structural features that were essential for the inhibitory activity of benzimidazoles were characterized. A molecular dynamics study revealed that the induced fit effect between NS5B and its substrate may be responsible for the inferiority of the receptor-based CoMFA and CoMSIA models. The binding-free energy calculated using the MM/PBSA method correlated well with the experimental results and revealed that the van der Waals and electrostatic interactions most contributed to the binding. In addition, energetically favorable NS5B residues were identified by the per-residue decomposition of binding-free energy. The results presented in this work provide meaningful information for the design of novel benzimidazole inhibitors targeting the NS5B polymerase.Communicated by Ramaswamy H. Sarma.