Artesunate induces substantial topological alterations in the SARS-CoV-2 Nsp1 protein structure

In vitro reconstitution of SARS-CoV-2 Nsp1-induced mRNA cleavage reveals the key roles of the N-terminal domain of Nsp1 and the RRM domain of eIF3g

SARS CoV-2 nonstructural protein 1 (Nsp1) is the major pathogenesis factor that inhibits host translation using a dual strategy of impairing initiation and inducing endonucleolytic cleavage of cellular mRNAs. To investigate the mechanism of cleavage, we reconstituted it in vitro on β-globin, EMCV IRES, and CrPV IRES mRNAs that use unrelated initiation mechanisms. In all instances, cleavage required Nsp1 and only canonical translational components (40S subunits and initiation factors), arguing against involvement of a putative cellular RNA endonuclease. Requirements for initiation factors differed for these mRNAs, reflecting their requirements for ribosomal attachment. Cleavage of CrPV IRES mRNA was supported by a minimal set of components consisting of 40S subunits and eIF3g's RRM domain. The cleavage site was located in the coding region 18 nt downstream from the mRNA entrance, indicating that cleavage occurs on the solvent side of the 40S subunit. Mutational analysis identified a positively charged surface on Nsp1's N-terminal domain (NTD) and a surface above the mRNA-binding channel on eIF3g's RRM domain that contain residues essential for cleavage. These residues were required for cleavage on all three mRNAs, highlighting general roles of the Nsp1 NTD and eIF3g's RRM domain in cleavage per se, irrespective of the mode of ribosomal attachment.

Degradation kinetics of artesunate for the development of an ex-tempore intravenous injection

Background

Artesunate is recommended by the World Health Organization (WHO) for parenteral treatment of severe Plasmodium falciparum malaria. However, artesunate is inherently unstable in an aqueous solution and hydrolyses rapidly after its preparation for injection. Therefore, the aim of the study was to evaluate the stabilizing effects of phosphate buffer and mannitol against short-term (ex-tempore) artesunate hydrolysis.

Methods

A HPLC–UV isocratic method was developed using a reversed-phase fused core column (HALO RP-C18) and a mobile phase consisting of a mixture of 45% ammonium formate 10 mM in water (pH 4.5) and 55% methanol. Artesunate was formulated as aqueous solutions using a design of experiment (DOE) to investigate the artesunate stabilizing effects of pH (8–10), phosphate buffer strength (0.3–0.5 M), and mannitol (0–0.22 mmol/mL). The solutions were incubated at predefined temperatures (5, 25, and 40 °C) with subsequent analysis. Arrhenius equation was applied to model and evaluate the stability results.

Results

The developed HPLC-based method using fused-core stationary phase allowed to selectively quantify artesunate in the presence of its main hydrolysis degradants; namely β-dihydroartemisinin (β-DHA) and α-dihydroartemisinin (α-DHA) within 10 min. By applying the Arrhenius equation, the rate of hydrolysis of the drug increased approximately by 3.4 as the temperature raised by 10 °C. Buffer strength was found to be the main factor affecting the hydrolysis rate constants at 5 and 25 °C (p < 0.05), the activation energy (p = 0.009), and the frequency factor (p = 0.045). However, the effect of the buffer was predominant on the activation energy and hydrolysis rate constants, revealing its stabilizing effect on the drug at lower buffer strength (0.3 M). Within the investigated range (pH = 8–10), pH was found to influence the activation energy, with a positive stabilizing effect in the pH range of 8–9. The addition of mannitol as stabilizing agent into artesunate aqueous formulation did not show an improved response.

Conclusion

Phosphate buffer was the main stability determining factor of artesunate in the aqueous intravenous (i.v.) formulation and was found to be more effective in stabilizing artesunate at a buffer strength of 0.3 M in pH 8–9, while mannitol lacked stabilizing effect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04278-4.

Antiparasitic Drugs against SARS-CoV-2: A Comprehensive Literature Survey

More than two years have passed since the viral outbreak that led to the novel infectious respiratory disease COVID-19, caused by the SARS-CoV-2 coronavirus. Since then, the urgency for effective treatments resulted in unprecedented efforts to develop new vaccines and to accelerate the drug discovery pipeline, mainly through the repurposing of well-known compounds with broad antiviral effects. In particular, antiparasitic drugs historically used against human infections due to protozoa or helminth parasites have entered the main stage as a miracle cure in the fight against SARS-CoV-2. Despite having demonstrated promising anti-SARS-CoV-2 activities in vitro, conflicting results have made their translation into clinical practice more difficult than expected. Since many studies involving antiparasitic drugs are currently under investigation, the window of opportunity might be not closed yet. Here, we will review the (controversial) journey of these old antiparasitic drugs to combat the human infection caused by the novel coronavirus SARS-CoV-2.

Artemisia Extracts and Artemisinin-Based Antimalarials for COVID-19 Management: Could These Be Effective Antivirals for COVID-19 Treatment?

As the world desperately searches for ways to treat the coronavirus disease 2019 (COVID-19) pandemic, a growing number of people are turning to herbal remedies. The Artemisia species, such as A. annua and A. afra, in particular, exhibit positive effects against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and COVID-19 related symptoms. A. annua is a source of artemisinin, which is active against malaria, and also exhibits potential for other diseases. This has increased interest in artemisinin's potential for drug repurposing. Artemisinin-based combination therapies, so-called ACTs, have already been recognized as first-line treatments against malaria. Artemisia extract, as well as ACTs, have demonstrated inhibition of SARS-CoV-2. Artemisinin and its derivatives have also shown anti-inflammatory effects, including inhibition of interleukin-6 (IL-6) that plays a key role in the development of severe COVID-19. There is now sufficient evidence in the literature to suggest the effectiveness of Artemisia, its constituents and/or artemisinin derivatives, to fight against the SARS-CoV-2 infection by inhibiting its invasion, and replication, as well as reducing oxidative stress and inflammation, and mitigating lung damage.

Synthesis, characterization, and theoretical investigation of 4-chloro-6(phenylamino)-1,3,5-triazin-2-yl)asmino-4-(2,4-dichlorophenyl)thiazol-5-yl-diazenyl)phenyl as potential SARS-CoV-2 agent

The synthesis of 4-chloro-6(phenylamino)-1,3,5-triazin-2-yl)amino-4-(2,4 dichlorophenyl)thiazol-5-yl-diazenyl)phenyl is reported in this work with a detailed structural and molecular docking study on two SARS-COV-2 proteins: 3TNT and 6LU7. The studied compound has been synthesized by the condensation of cyanuric chloride with aniline and characterized with various spectroscopic techniques. The experimentally obtained spectroscopic data has been compared with theoretical calculated results achieved using high-level density functional theory (DFT) method. Stability, nature of bonding, and reactivity of the studied compound was evaluated at DFT/B3LYP/6-31 + (d) level of theory. Hyper-conjugative interaction persisting within the molecules which accounts for the bio-activity of the compound was evaluated from natural bond orbital (NBO) analysis. Adsorption, Distribution, Metabolism, Excretion and Toxicity (ADMET) properties of the experimentally synthesized compound was studied to evaluate the pharmacological as well as in silico molecular docking against SARS-CoV-2 receptors. The molecular docking result revealed that the investigated compound exhibited binding affinity of −9.3 and −8.8 for protein 3TNT and 6LU7 respectively. In conclusion, protein 3TNT with the best binding affinity for the ligand is the most suitable for treatment of SARS-CoV-2.