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COVID-19 is a respiratory disease caused by SARS-CoV-2, an enveloped positive sense RNA virus. The SARS-CoV-2 spike glycoprotein, human angiotensin-converting enzyme 2 (ACE2) and human transmembrane protease serine 2 (TMPRSS2) are essential for the host cell-mediated viral entry. Targeting these proteins represent viable options to stop the first stage of infection and transmission. Hence, 97 alkaloids from African medicinal plants with reported antiviral activity were evaluated for this purpose via in silico studies. These alkaloids were docked for their interactions with SARS-CoV-2 spike glycoprotein, ACE2, and TMPRSS2. Top 20 alkaloids with highest binding affinities were further screened for their interactions with spike glycoprotein of SARS-CoV and MERS-CoV, and with ACE2-SARS-CoV-2 receptor-binding domain complex (ACE2-RBD). The energy profiling, molecular dynamics simulation (MDS), binding free energy base on Molecular Mechanics/Generalized Born Surface Area (MMGBSA), clustering of MDS trajectories, and virtual physicochemical and pharmacokinetic screening of the best docked alkaloids were performed. Results revealed that more than 15 alkaloids interacted better than the reference compounds. 10–Hydroxyusambarensine and Cryptospirolepine were docked in a similar binding pattern to the S1-specificy pocket of TMPRSS2 as camostat (reference inhibitor). The strong binding affinities, stability of the alkaloid-protein complexes and amino acid interactions displayed by cryptospirolepine, 10-hydroxyusambarensine, and cryptoquindoline with important binding hotspots of the proteins suggest these alkaloids have the potential of altering the capacity of SARS-CoV-2 membrane mediated host cell entry. Further in vitro and in vivo evaluation of these “drug-like” alkaloids as potential inhibitors of coronavirus cell entry is proposed. Communicated by Ramaswamy H. Sarma

The global challenge to the treatment of malaria is mainly the occurrence of resistance of malaria parasites to conventionally used antimalarials. Artesunate, a semisynthetic artemisinin compound, and other artemisinin derivatives are currently used in combination with selected active antimalarial drugs in order to prevent or delay the emergence of resistance to artemisinin derivatives. Several methods, such as preparation of hybrid compounds, combination therapy, chemical modification and the use of synthetic materials to enhance solubility and delivery of artesunate, have been employed over the years to improve the antimalarial activity of artesunate. Each of these methods has advantages it bestows on the efficacy of artesunate. This review discussed the various methods employed in enhancing the antimalarial activity of artesunate and delaying the emergence of resistance of parasite to it.

Corona Virus Disease 2019 (COVID-19) is a pandemic caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Exploiting the potentials of phytocompounds is an integral component of the international response to this pandemic. In this study, a virtual screening through molecular docking analysis was used to screen a total of 226 bioactive compounds from African herbs and medicinal plants for direct interactions with SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). From these, 36 phytocompounds with binding affinities higher than the approved reference drugs (remdesivir and sobosivir), were further docked targeting the active sites of SARS-CoV-2, as well as SARS-CoV and HCV RdRp. A hit list of 7 compounds alongside two positive controls (remdesivir and sofosbuvir) and two negative controls (cinnamaldehyde and Thymoquinone) were further docked into the active site of 8 different conformations of SARS-CoV-2 RdRp gotten from molecular dynamics simulation (MDS) system equilibration. The top docked compounds were further subjected to predictive druglikeness and ADME/tox filtering analyses. Drugable alkaloids (10’–hydroxyusambarensine, cryptospirolepine, strychnopentamine) and flavonoids (usararotenoid A, and 12α-epi-millettosin), were reported to exhibit strong affinity binding and interactions with key amino acid residues in the catalytic site, the divalent-cation–binding site, and the NTP entry channel in the active region of the RdRp enzyme as the positive controls. These phytochemicals, in addition to other promising antivirals such as remdesivir and sofosbuvir, may be exploited towards the development of a cocktail of anti-coronavirus treatments in COVID-19. Experimental studies are recommended to validate these study.

An in-house library of 173 phytocompound structures from Vernonia amygdalina and Occinum gratissimum was screened against the active region of 3-Chymotrypsin-Like Protease (3CL pro ) of SARS-CoV-2 in silico. Based on docking scores and reference inhibitors, a hit-list of 21 phytocompounds, with binding energies ranging from − 7.2 to -8.0 kcal/mol, was initially generated. Further docking against the 3CL pro of related coronaviruses (SARS-CoV and MERS-CoV), docking to 5 different representative conformations generated from the cluster analysis of SARS-CoV-2 3CL pro molecular dynamics simulation (MDS) trajectories, and in silico drug-likeness analyses, revealed two drug-like terpenoid structures as promising non-covalent inhibitors of SARS-CoV-2 3CL Pro viz: neoandrographolide and vernolide. These terpenoid structures are accommodated within the substrate-binding pocket, and interacted with the catalytic dyad, the oxyanion loop (residues 138-145), and the S1/S2 subsites of the enzyme active site. With the aid of an array of hydrogen bonds and hydrophobic interactions with residues 142-145, these phytocompounds may stabilize the conformation of the exible oxyanion loop; and thereby interfere with the tetrahedral oxyanion intermediate formation during proteolytic cleavage. Molecular dynamics simulation and binding free energy calculation further revealed that the terpenoid-enzyme complexes exhibit strong interactions and structural stability, which could be adapted for experimental models.

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Background Targeting viral cell entry proteins is an emerging therapeutic strategy for inhibiting the first stage of SARS-CoV-2 infection. In this study, 106 bioactive terpenoids from African medicinal plants were screened through molecular docking analysis against human angiotensin-converting enzyme 2 (hACE2), human transmembrane protease serine 2 (TMPRSS2), and the spike (S) proteins of SARS-CoV-2, SARS-CoV, and MERS-CoV. In silico absorption-distribution-metabolism-excretion-toxicity (ADMET) and drug-likeness prediction, molecular dynamics (MD) simulation, binding free energy calculations, and clustering analysis of MD simulation trajectories were performed on the top docked terpenoids to respective protein targets. Results The results revealed eight terpenoids with high binding tendencies to the catalytic residues of different targets. Two pentacyclic terpenoids (24-methylene cycloartenol and isoiguesteri) interacted with the hACE2 binding hotspots for the SARS-CoV-2 spike protein, while the abietane diterpenes were found accommodated within the S1-specificity pocket, interacting strongly with the active site residues TMPRSS2. 3-benzoylhosloppone and cucurbitacin interacted with the RBD and S2 subunit of SARS-CoV-2 spike protein respectively. These interactions were preserved in a simulated dynamic environment, thereby, demonstrating high structural stability. The MM-GBSA binding free energy calculations corroborated the docking interactions. The top docked terpenoids showed favorable drug-likeness and ADMET properties over a wide range of molecular descriptors. Conclusion The identified terpenoids from this study provides core structure that can be exploited for further lead optimization to design drugs against SARS-CoV-2 cell-mediated entry proteins. They are therefore recommended for further in vitro and in vivo studies towards developing entry inhibitors against the ongoing COVID-19 pandemic.

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