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.

Synthesis and characterization of the antitubercular phenazine lapazine and development of PLGA and PCL nanoparticles for its entrapment.

The aim of this work was to develop and characterize nanoparticles as carriers of lapazine, a phenazine derived from ß-lapachone; its antimycobacterial activity is described for the first time as a potential treatment for tuberculosis. The lapazine was synthesized, and by using gas chromatography coupled to a flame ionization detector, it was possible to evaluate its purity degree of almost 100%. For better elucidation of the molecular structure, mass spectroscopy and 1H NMR were carried out and compared to the literature values. Lapazine was assayed in vitro against H37Rv Mycobacterium tuberculosis and a rifampicin-resistant strain, with minimum inhibitory concentration values of 3.00 and 1.56 µg mL(-1), respectively. The nanoparticles showed a polydispersity index of 0.16,mean diameter of 188.5 ± 1.7 mm, zeta potential of -15.03 mV, and drug loading of 54.71 mg g(-1) for poly-ε-caprolactone (PCL) nanoparticles and a polydispersity index of 0.318,mean diameter of 197.4 ± 2.7 mm, zeta potential of -13.43 mV and drug loading of 137.07 mg g(-1) for poly(DL-lactide-co-glycolide) (PLGA) nanoparticles. These results indicate that both polymeric formulations have good characteristics as potential lapazine carriers in the treatment of tuberculosis.

Chemical characterization of bio-oils using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

The liquid product obtained via the biomass flash pyrolysis is commonly called bio-oil or pyrolysis oil. Bio-oils can be used as sources for chemicals or as fuels, primarily in mixtures or emulsions with fossil fuels. A detailed chemical characterization of bio-oil is necessary to determine its potential uses. Such characterization demands a powerful analytical technique such as comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS). Limited chemical information can be obtained from conventional gas chromatography coupled mass spectrometry (GC-MS) because of the large number of compounds and coelutions. Thus, GC×GC-TOFMS was used for the individual identification of bio-oil components from two samples prepared via the flash pyrolysis of empty palm fruit bunch and pine wood chips. To the best of our knowledge, few papers have reported comprehensive two-dimensional gas chromatography (GC×GC) for bio-oil analysis. Many classes of compounds such as phenols, benzenediols, cyclopentenones, furanones, indanones and alkylpyridines were identified. Several coelutions present in the GC-MS were resolved using GC×GC-TOFMS. Many peaks were detected for the samples by GC-MS (~166 and 129), but 631 and 857 were detected by GC×GC-TOFMS, respectively. The GC×GC-TOFMS analyses indicated that the major classes of components (analytes>0.5% relative area) in the two bio-oil samples are ketones, cyclopentenones, furanones, furans, phenols, benzenediols, methoxy- and dimethoxy-phenols and sugars. In addition, esters, aldehydes and pyridines were found for sample obtained from empty palm fruit bunch, while alcohols and cyclopentanediones were found in sample prepared from pine wood chips indicating different composition profiles due to the biomass sources. The elucidation of the composition of empty fruit bunch and pine wood chips bio-oils indicates that these oils are suitable for the production of value-added chemicals. The high quantity of phenol in the bio-oil of empty palm fruit bunch is of interest because phenol isolated from the bio-oil could provide an alternative to the phenol obtained from petroleum. The anhydrosugars found mainly in the bio-oil sample of pine wood chips can be isolated and fermented to produce ethanol or lipids. GC×GC-TOFMS can be used to increase the knowledge of the chemical composition of bio-oils allowing the improved usage of this attractive renewable energy source in bio-fuels.

Activity of ß-lapachone derivatives against rifampicin-susceptible and -resistant strains of Mycobacterium tuberculosis.

The increase of incidence of tuberculosis (TB) with resistant strains and HIV co-infection has reinforced the necessity of developing new drugs for its treatment. The reaction of naphthoquinones with aromatic or aliphatic aldehydes in the presence of ammonium acetate led to the synthesis of the three ß-lapachone derivatives (naphthoimidazoles) that were tested in this study. Phenazines were prepared by the reaction of the respective naphtoquinone with o-phenylenediamine in acetic acid under reflux. The antimicrobial activity of the derivatives was evaluated in vitro against Mycobacterium tuberculosis H37Rv (ATCC 27294) and the rifampicin-resistant strain (ATCC 35338) containing a His-526-Tir mutation in the rpoB gene. Using the Resazurin Microtiter Assay (REMA) method, bioactive molecules were observed in the susceptible and resistant strains with MICs ranging from 2.2 µM to 17 µM. The naphthoimidazoles with p-toluyl and indolyl group attached to the imidazole ring were more active against the H37Rv strain (MIC 9.12 µM and 4.2 µM, respectively) than the rifampicin-resistant strain (MIC 8.3 µM and 17 µM, respectively). The phenazine with the allyl-pyran group was most active among the two strains and had an MIC of 2.2 mM. These results show the potential of these molecules as prototypes for future drugs used in treating TB.

Mechanism of action of novel naphthofuranquinones on rat liver microsomal peroxidation.

In order to elucidate the effect on mammal systems of new derivatives from 2-hydroxy-3-allyl-naphthoquinone, alpha-iodinated naphthofuranquinone (NPPN-3223), beta-iodinated naphthofuranquinone (NPPN-3222) and beta-methyl naphthofuranquinone (NPPN-3226) synthesized as possible trypanocidal agents, their effect on rat liver microsomal lipid peroxidation was investigated. They (a) inhibited NADPH-dependent, iron-catalyzed microsomal rat liver lipid peroxidation; (b) did not inhibit the tert-butyl hydroperoxide-dependent lipid peroxidation; (c) did not inhibit ascorbate-lipid peroxidation with the exception of NPPN-3226 which did inhibit it; (d) stimulated NADPH oxidation and microsomal oxygen uptake; (e) increased superoxide anion formation by NADPH-supplemented microsomes and (f) stimulated ascorbate oxidation. The three drugs were reduced to their seminaphthofuranquinone radical by the liver NADPH-P450 reductase system, as detected by ESR measurements. These results support the hypothesis that naphthofuranquinones reduction by microsomal NADPH-P450 reductase and semiquinone oxidation by molecular oxygen diverts electrons, preventing microsomal lipid peroxidation. In addition, hydroquinones and/or semiquinones formed by naphthofuranquinones reduction would be capable of lipid peroxidation inhibition and on interacting with the lipid peroxide radicals can lead to an antioxidant effect as we suggested for NPPN-3226 in close agreement to the inhibition of ascorbate-lipid peroxidation. Due to the properties of these molecules and their incoming structure developments, naphthofuranquinones would be considered as potentially promising therapeutic agents, mainly against Chagas disease.

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.

A macrolactone from benzo[a]phenazine with potent activity against Mycobacterium tuberculosis.

We report here an alternative to the MCPBA or ozonolysis-based oxidation methods of quinoxaline-featuring compounds prepared from beta-lapachones. The use of peracetic acid allowed a simple preparation of the corresponding macrolactones by cleavage of the ring system. These lactones were evaluated for their antimycobacterial potential and compound 4 turned out to have an MIC of 0.62 microg per mL on Mycocabteriumtuberculosis H37Rv. These results justify further research into its value as a potential lead for an original treatment of tuberculosis.

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.

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.

A reação das naphthoquinona-oximas (3) e (4) com diazometano fornece diretamente, em uma etapa, os oxazóis (5) e (6), respectivamente.

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.