Searching for potential drugs against SARS-CoV-2 through virtual screening on several molecular targets

The acute respiratory syndrome caused by the SARS-CoV-2, known as COVID-19, has been ruthlessly tormenting the world population for more than six months. However, so far no effective drug or vaccine against this plague have emerged yet, despite the huge effort in course by researchers and pharmaceutical companies worldwide. Willing to contribute with this fight to defeat COVID-19, we performed a virtual screening study on a library containing Food and Drug Administration (FDA) approved drugs, in a search for molecules capable of hitting three main molecular targets of SARS-CoV-2 currently available in the Protein Data Bank (PDB). Our results were refined with further molecular dynamics (MD) simulations and MM-PBSA calculations and pointed to 7 multi-target hits which we propose here for experimental evaluation and repurposing as potential drugs against COVID-19. Additional rounds of docking, MD simulations and MM-PBSA calculations with remdesivir suggested that this compound can also work as a multi-target drug against SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

The effects on Trypanosoma cruzi of novel synthetic naphthoquinones are mediated by mitochondrial dysfunction

Despite ongoing efforts, the current treatment for Chagas disease is still unsatisfactory, mainly because of the severe side effects and variable efficacy of the available nitroheterocycles. Our group has been assaying natural quinones isolated from Brazilian flora, and their derivatives, as alternative chemotherapeutic agents against Trypanosoma cruzi. From C-allyl lawsone three naphthofuranquinones were synthesized, which were active against trypomastigotes and epimastigotes. Here, we further investigated the activity and the mechanisms of action of these quinones. They exhibited powerful effects on intracellular amastigotes, presenting low toxicity to the host cells. Ultrastructural analyses of treated epimastigotes and trypomastigotes indicated a potent effect of the three naphthofuranquinones on the parasite mitochondrion, which appeared drastically swollen and with a washed-out matrix profile. Fluorescence-activated cell sorting analysis of rhodamine 123-stained T. cruzi showed that the three naphthofuranquinones caused a potent dose-dependent collapse of the mitochondrial membrane potential, especially in the epimastigote form. Naphthofuranquinones also decreased specifically mitochondrial complex I-III activity in both epimastigotes and trypomastigotes, parallel to a reduction in succinate-induced oxygen consumption. Mitochondrial hydrogen peroxide formation was also increased in epimastigotes after treatment with the naphthofuranquinones. Our results indicate that the trypanocidal action of the naphthofuranquinones is associated with mitochondrial dysfunction, leading to increased reactive oxygen species generation and parasite death.

3-(2,4-Dibromo-anilino)-2,2-dimethyl-2,3-dihydro-naphtho[1,2-b]furan-4,5-dione: a new substituted aryl-amino nor-β-lapachone derivative

The title compound, C₂₀H₁₅Br₂NO₃, shows the furan ring to adopt a half-chair conformation and the two ring systems to be approximately perpendicular [dihedral angle = 71.0 (2)°]. In the crystal structure, inter­molecular C—H⋯O contacts link the mol­ecules.

Naphthoquinoidal [1,2,3]-triazole, a new structural moiety active against Trypanosoma cruzi

[1,2,3]-Triazole derivatives of nor-beta-lapachone were synthesized and assayed against the infective bloodstream trypomastigote form of Trypanosoma cruzi, the etiological agent of Chagas disease. All the derivatives were more active than the original quinones, with IC(50)/1 day values in the range of 17 to 359 microM, the apolar phenyl substituted triazole 6 being the most active compound. These triazole derivatives of nor-beta-lapachone emerge as interesting new lead compounds in drug development for Chagas disease.

Applications of counter-current chromatography in organic synthesis purification of heterocyclic derivatives of lapachol

This work describes the application of counter-current chromatography (CCC) as a useful, fast and economic alternative for the isolation and purification of heterocyclic derivatives from lapachol and beta-lapachone, two naturally occurring compounds from Tabebuia species, and nor-beta-lapachone, a synthetic congener of lapachol. The discussed data comprise four examples of purification of synthetic reactions with different solvent systems - the mixture of the oxazole and the imidazole from beta-lapachone; the quinoxaline from nor-beta-lapachone; and the purification of the N-oxides from the quinoxaline and the phenazine from nor-beta-lapachone from their respective not fully reacted substrates by means of aqueous reversed- and normal-phase elution modes and non-aqueous solvent systems. Traditional purification of these reaction products by silica gel column chromatography demanded a large amount of solvent and time and, in some cases, serious degradation of the products occurred, leading to low yield of the reaction. High-speed counter-current chromatography (HSCCC) was used as an alternative to optimize the process and raise the yield of the reactions.

1,4- Addition of diazomethane to a heterodiene: a direct preparation of the oxazolic ring

The reaction of naphthoquinone-oximes (3) and (4) with diazomethane yields directly, in one step, the oxazoles (5) and (6), respectively.

Synthesis of naphthofuranquinones with activity against Trypanosoma cruzi

Four new naphthofuranquinones, obtained from 2-hydroxy-3-allyl-naphthoquinone (1) and nor-lapachol (2), have their structures established by physical and X-ray analysis and their activity evaluated against Trypanosoma cruzi. Compounds 3 and 4 were obtained by addition of iodine to 1 followed by cyclization generating a furan ring. Compound 5 was obtained through the acid-catalyzed reaction by dissolution of 1 in sulfuric acid. Compound 6 was synthesized by addition of bromine and aniline to 2. The IC(50)/24 h for 3-6 in assays with T. cruzi trypomastigotes was between 157 and 640 microM, while the value for crystal violet was 536.0 +/- 3.0 microM. Compounds 3-5 also inhibited epimastigote proliferation. The trypanocidal activity of the new naphthofuranquinones endowed with redox properties reinforces a rational approach in the chemotherapy of Chagas' disease.