Inhibitory mechanism of clioquinol and its derivatives at the exopeptidase site of human angiotensin-converting enzyme-2 and receptor binding domain of SARS-CoV-2 viral spike.

The outbreak of SARS-CoV-2 infections around the world has prompted scientists to explore different approaches to develop therapeutics against COVID-19. This study focused on investigating the mechanism of inhibition of clioquinol (CLQ) and its derivatives (7-bromo-5-chloro-8-hydroxyquinoline (CLBQ), 5, 7-Dichloro-8-hydroxyquinoline (CLCQ)) against the viral glycoprotein, and human angiotensin-converting enzyme-2 (hACE-2) involved in SARS-CoV-2 entry. The drugs were docked at the exopeptidase site of hACE-2 and receptor binding domain (RBD) sites of SARS-CoV-2 Sgp to calculate the binding affinity of the drugs. To understand and establish the inhibitory characteristics of the drugs, molecular dynamic (MD) simulation of the best fit docking complex performed. Evaluation of the binding energies of the drugs to hACE-2 after 100 ns MD simulations revealed CLQ to have the highest binding energy value of -40.4 kcal/mol close to MLN-7640 (-45.4 kcal/mol), and higher than the exhibited values for its derivatives: CLBQ (-34.5 kcal/mol) and CLCQ (-24.8 kcal/mol). This suggests that CLQ and CLBQ bind more strongly at the exopeptidase site than CLCQ. Nevertheless, the evaluation of binding affinity of the drugs to SARS-CoV-2 Sgp showed the drugs are weakly bound at the RBD site, with CLBQ, CLCQ, CLQ exhibiting relatively low energy values of -16.8 kcal/mol, -16.34 kcal/mol, -12.5 kcal/mol, respectively compared to the reference drug, Bisoxatin (BSX), with a value of -25.8 kcal/mol. The structural analysis further suggests decrease in systems stability and explain the mechanism of inhibition of clioquinol against SARS-CoV-2 as reported in previous in vitro study.Communicated by Ramaswamy H. Sarma.

Inhibitory mechanism of Ambroxol and Bromhexine Hydrochlorides as potent blockers of molecular interaction between SARS-CoV-2 spike protein and human angiotensin-converting Enzyme-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects the host cells through interaction of its spike protein with human angiotensin-converting enzyme 2 (hACE-2). High binding affinity between the viral spike protein and host cells hACE-2 receptor has been reported to enhance the viral infection. Thus, the disruption of this molecular interaction will lead to reduction in viral infectivity. This study, therefore, aimed to analyze the inhibitory potentials of two mucolytic drugs; Ambroxol hydrochlorides (AMB) and Bromhexine hydrochlorides (BHH), to serve as potent blockers of these molecular interactions and alters the binding affinity/efficiency between the proteins employing computational techniques. The study examined the effects of binding of each drug at the receptor binding domain (RBD) of the spike protein and the exopeptidase site of hACE-2 on the binding affinity (ΔGbind) and molecular interactions between the two proteins. Binding affinity revealed that the binding of the two drugs at the RBD-ACE-2 site does not alter the binding affinity and molecular interaction between the proteins. However, the binding of AMB (-56.931 kcal/mol) and BHH (-46.354 kcal/mol) at the exopeptidase site of hACE-2, significantly reduced the binding affinities between the proteins compared to the unbound, ACE-2-RBD complex (-64.856 kcal/mol). The result further showed the two compounds have good affinity at the hACE-2 site, inferring they might be potent inhibitors of hACE-2. Residue interaction networks analysis further revealed the binding of the two drugs at the exopeptidase site of hACE-2 reduced the number of interacting amino residues, subsequently leading to loss of interactions between the two proteins, with BHH showing better reduction in the molecular interaction and binding affinity than AMB. The result of the structural analyses additionally, revealed that the binding of the drugs considerably influences the dynamic of the complexes when compared to the unbound complex. The findings from this study suggest the binding of the two drugs at the exopeptidase site reduces the binding effectiveness of the proteins than their binding at the RBD site, and consequently might inhibit viral attachment and entry.

Molecular dynamic mechanism(s) of inhibition of bioactive antiviral phytochemical compounds targeting cytochrome P450 3A4 and P-glycoprotein.

P-glycoprotein (ABCB1) and cytochrome P450 3A4 (CYP3A4) metabolize almost all known human immunodeficiency virus' protease inhibitor drugs (PIs). Over induction of these proteins' activities has been linked to rapid metabolism of PIs which are then pumped out of the circulatory system, eventually leading to drug-resistance in HIV-positive patients. This study aims to determine, with the use of computational tools, the inhibitory potential of four phytochemical compounds (PCs) (epigallocatechin gallate (EGCG), kaempferol-7-glucoside (K7G), luteolin (LUT) and ellagic acid (EGA)) in inhibiting the activities of these drug-metabolizing proteins. The comparative analysis of the MM/GBSA results revealed that the binding affinity (ΔGbind) of EGCG and K7G for CYP3A4 and ABCB1 are higher than LUT and EGA and fall between the ΔGbind of the inhibitors of CYP3A4 and ABCB1 (Ritonavir (strong inhibitor) and Lopinavir (moderate inhibitor)). The structural analysis (RMSD, RMSF, RoG and protein-ligand interaction plots) also confirmed that EGCG and K7G showed similar inhibitory activities with the inhibitors. The study has shown that EGCG and K7G have inhibitory activities against the two proteins and assumes they could decrease intracellular efflux of PIs, consequently increasing the optimal concentration of PIs in the systemic circulation.Communicated by Ramaswamy H. Sarma.

Design and synthesis of pyrazolone-based compounds as potent blockers of SARS-CoV-2 viral entry into the host cells.

SARS-CoV-2 are enveloped positive-stranded RNA viruses that replicate in the cytoplasm. It relies on the fusion of their envelope with the host cell membrane to deliver their nucleocapsid into the host cell. The spike glycoprotein (S) mediates virus entry into cells via the human Angiotensin-converting enzyme 2 (hACE2) protein located on many cell types and tissues' outer surface. This study, therefore, aimed to design and synthesize novel pyrazolone-based compounds as potential inhibitors that would interrupt the interaction between the viral spike protein and the host cell receptor to prevent SARS-CoV 2 entrance into the cell. A series of pyrazolone compounds as potential SARS-CoV-2 inhibitors were designed and synthesized. Employing computational techniques, the inhibitory potentials of the designed compounds against both spike protein and hACE2 were evaluated. Results of the binding free energy from the in-silico analysis, showed that three compounds (7i, 7k and 8f) and six compounds (7b, 7h, 7k, 8d, 8g, and 8h) showed higher and better binding high affinity to SARS-CoV-2 Sgp and hACE-2, respectively compared to the standard drugs cefoperazone (CFZ) and MLN-4760. Furthermore, the outcome of the structural analysis of the two proteins upon binding of the inhibitors showed that the two proteins (SARS-CoV-2 Sgp and hACE-2) were stable, and the structural integrity of the proteins was not compromised. This study suggests pyrazolone-based compounds might be potent blockers of the viral entry into the host cells.

Modulatory influences of antiviral bioactive compounds on cell viability, mRNA and protein expression of cytochrome P450 3A4 and P-glycoprotein in HepG2 and HEK293 cells.

The induction of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (ABCB1) influence drug plasma, and eventually decreases the drugs' therapeutic effects. The effects of Plant-derived compounds (PCs) on drug-metabolising proteins are largely unknown. This study investigated the cytotoxicity, cell viability profiles and regulatory influences of four PCs (epigallocatechin gallate (EGCG), kaempferol-7-glucoside (K7G), luteolin (LUT) and ellagic acid (EGA)) on the mRNA and protein expressions of CYP3A4 and ABCB1 in HepG2 and HEK293 cells. After treatment with the PCs (0-400 µM) for 24 h, 80% (IC20) and 50% (IC50) cell viability were determined. The PCs were not toxic to HepG2 (ATP levels increased at IC20, insignificant change in LDH (lactate dehydrogenase) with the exception of LUT, and ABCB1 protein expressions decreased. The PCs decreased CYP3A4 at IC20 (except LUT), EGCG and K7G at IC20 decreased mRNA expression. For HEK293 cells, no significant change in ATP, except for EGCG IC20 and K7G IC50 which decreased and increased, respectively. LDH decreased at IC20, but LUT IC50 significant increase LDH. ABCB1 protein expression increased at both IC20 and IC50, but LUT and EGA at IC50 decreased mRNA expression. The PCs at IC20, and IC50 of LUT, K7G and of EGCG may enhance drug bioavailability.

Role of dietary maize formulations in the healing of experimental acetic acid induced ulcerative colitis in male rats.

Dietary factors do not only contribute to remission of diseases but also play important roles in the progression of medical conditions. We investigated the effect of different formulations of maize diets on the healing of experimental acetic acid-induced ulcerative colitis (UC) in male rats. Thirty-five (35) male Wistar rats (150-170 g) were randomly divided into control (CTR), UC, UC + high maize diet (HMD), UC + low maize diet (LMD), and UC + maize-free diet (MFD) groups. CTR, UC, UC + HMD, UC + LMD, and UC + MFD groups were administered different formulations of dietary maize ranging from 0% to 70%. Body weight change (BWC), colon weight, macroscopic ulcer score, catalase, glutathione (GSH), tumor necrosis factor-α (TNF-α), myeloperoxidase, diarrhea score, superoxide dismutase (SOD), Ki-67 expression, and histological studies were done. Results were analyzed using SPSS 23. UC + LMD and UC + MFD groups showed a duration-dependent reduction in negative BWC, respectively. When compared with UC group, UC + LMD and UC + MFD significantly increased (P < 0.05) GSH and SOD respectively but had no effect on TNF-α and diarrhea score. UC + HMD increased diarrhea and macroscopic ulcer scores with Ki-67 expression highest in UC + MFD. The study indicated that consumption of either LMD or maize-free diet by colitic rats relatively enhanced healing of UC.

The pharmacokinetic properties of HIV-1 protease inhibitors: A computational perspective on herbal phytochemicals.

Acquired Immune Deficiency Syndrome is the most severe phase of Human Immunodeficiency Virus (HIV) infection. Recent studies have seen an effort to isolate phytochemicals from plants to repress HIV, but less studies have focused on the effects of these phytochemicals on the activities of enzymes/transporters involved in the metabolism of these drugs, which is one of the aims of this study and, to examine the antiviral activity of these compounds against HIV-1 protease enzyme using computational tools. Centre of Awareness-Food Supplement (COA®-FS) herbal medicine, has been said to have potential anti-HIV features. SWISSTARGETPREDICTION and SWISSADME servers were used for determination of the enzymes/transporters involved in the metabolism of these protease inhibitor drugs, (PIs) (Atazanavir, Lopinavir, Darunavir, Saquinavir) and the effects of the selected phytochemicals on the enzymes/transporters involved in the metabolism of these PIs. Using Computational tools, potential structural inhibitory activities of these phytochemicals were explored. Two sub-families of Cytochrome P450 enzymes (CYP3A4 and CYP2C19) and Permeability glycoprotein (P-gp) were predicted to be involved in metabolism of the PIs. Six phytochemicals (Geranin, Apigenin, Fisetin, Luteolin, Phthalic acid and Gallic acid) were predicted to be inhibitors of CYP3A4 and, may slowdown elimination of PIs thereby maintain optimal PIs concentrations. Free binding energy analysis for antiviral activities identified four phytochemicals with favourable binding landscapes with HIV-1 protease enzyme. Epigallocatechin gallate and Kaempferol-7-glucoside exhibited pronounced structural evidence as potential HIV-1 protease enzyme inhibitors. This study acts as a steppingstone toward the use of natural products against diseases that are plagued with adverse drug-interactions.