Structure-based discovery of thiosemicarbazones as SARS-CoV-2 main protease inhibitors

Aim: Discovery of novel SARS-CoV-2 main protease (Mpro) inhibitors using a structure-based drug discovery strategy. Materials & methods: Virtual screening employing covalent and noncovalent docking was performed to discover Mpro inhibitors, which were subsequently evaluated in biochemical and cellular assays. Results: 91 virtual hits were selected for biochemical assays, and four were confirmed as reversible inhibitors of SARS CoV-2 Mpro with IC50 values of 0.4-3 μM. They were also shown to inhibit SARS-CoV-1 Mpro and human cathepsin L. Molecular dynamics simulations indicated the stability of the Mpro inhibitor complexes and the interaction of ligands at the subsites. Conclusion: This approach led to the discovery of novel thiosemicarbazones as potent SARS-CoV-2 Mpro inhibitors.

Do Drug-likeness Rules Apply to Oral Prodrugs?

This paper describes a comparative analysis of the physicochemical and structural properties of prodrugs and their corresponding drugs with regard to drug-likeness rules. The dataset used in this work was obtained from the DrugBank. Sixty-five pairs of prodrugs/drugs were retrieved and divided into the following categories: carrier-linked to increase hydrophilic character, carrier-linked to increase absorption, and bioprecursors. We compared the physicochemical properties related to drug-likeness between prodrugs and drugs. Our results show that prodrugs do not always follow Lipinski's Rule of 5, especially as we observed 15 prodrugs with more than 10 hydrogen bond acceptors and 18 with a molecular weight greater than 500 Da. This fact highlights the importance of extending Lipinski's rules to encompass other parameters as both strategies (filtering of drug-like chemical libraries and prodrug design) aim to improve the bioavailability of compounds. Therefore, critical reasoning is fundamental to determine whether a structure has drug-like properties or could be considered a potential orally active compound in the drug-design pipeline.

A clioquinol-containing Pluronic® F127 polymeric micelle system is effective in the treatment of visceral leishmaniasis in a murine model

A clioquinol (ICHQ)-containing Pluronic^® F127 polymeric micelle system (ICHQ/Mic) was recently shown to be effective against Leishmania amazonensis infection in a murine model. In the present study, ICHQ/Mic was tested against L. infantum infection. BALB/c mice (n = 12 per group) were infected with L. infantum stationary promastigotes through subcutaneous injection and, 45 days after challenge, received saline or were treated via the subcutaneous route with empty micelles, ICHQ or ICHQ/Mic. In addition, animals were treated with miltefosine by the oral route, as a drug control. Half of the animals were euthanized 1 and 15 days after treatment, aiming to evaluate two endpoints after therapy, when parasitological and immunological parameters were investigated. Results showed that the treatment using miltefosine, ICHQ or ICHQ/Mic induced significantly higher anti-parasite IFN-γ, IL-12, GM-CSF, nitrite and IgG2a isotype antibody levels, which were associated with low IL-4 and IL-10 production. In addition, a higher frequency of IFN-γ and TNF-α-producing CD4⁺ and CD8⁺ T-cells was found in these animals. The parasite load was evaluated in distinct organs, and results showed that the treatment using miltefosine, ICHQ or ICHQ/Mic induced significant reductions in organic parasitism in the treated and infected mice. A comparison between the treatments suggested that ICHQ/Mic was the most effective in inducing a highly polarized Th1-type response, as well as reducing the parasite load in significant levels in the treated and infected animals. Data obtained 15 days after treatment suggested maintenance of the immunological and parasitological responses. In conclusion, ICHQ/Mic could be considered in future studies for the treatment of visceral leishmaniasis.

New 99mTc-Labeled Digitoxigenin Derivative for Cancer Cell Identification

In recent years, cardiac glycosides (CGs) have been investigated as potential antiviral and anticancer drugs. Digitoxigenin (DIG) and other CGs have been shown to bind and inhibit Na⁺/K⁺-adenosinetriphosphatase (ATPase). Tumor cells show a higher expression rate of the Na⁺/K⁺-ATPase protein or a stronger affinity towards the binding of CGs and are therefore more prone to CGs than non-tumor cells. Cancer imaging techniques using radiotracers targeted at specific receptors have yielded successful results. Technetium-99m (^99mTc) is one of the radionuclides of choice to radiolabel pharmaceuticals because of its favorable physical and chemical properties along with reasonable costs. Herein, we describe a new Na⁺/K⁺-ATPase targeting radiotracer consisting of digitoxigenin and diethylenetriaminepentaacetic acid (DTPA), a bifunctional chelating ligand used to prepare ^99mTc-labeled complexes, and its evaluation as an imaging probe. We report the synthesis and characterization of the radiolabeled compound including stability tests, blood clearance, and biodistribution in healthy mice. Additionally, we investigated the binding of the compound to A549 human non-small-cell lung cancer cells and the inhibition of the Na⁺/K⁺-ATPase by the labeled compound in vitro. The ^99mTc-labeled DTPA-digitoxigenin (^99mTc-DTPA-DIG) compound displayed high stability in vitro and in vivo, a fast renal excretion, and a specific binding towards A549 cancer cells in comparison to non-tumor cells. Therefore, ^99mTc-DTPA-DIG could potentially be used for non-invasive visualization of tumor lesions by means of scintigraphic imaging.

The phthalimide analogues N-3-hydroxypropylphthalimide and N-carboxymethyl-3-nitrophthalimide exhibit activity in experimental models of inflammatory and neuropathic pain

BACKGROUND

Phthalimide analogues devoid of the glutarimide moiety exhibit multiple biological activities, thus making them candidates for the treatment of patients with different diseases, including those with inflammatory and painful disorders. In the present study, the activities of five phthalimide analogues devoid of the glutarimide moiety (N-hydroxyphthalimide, N-hydroxymethylphthalimide, N-3-hydroxypropylphthalimide, N-carboxy-3-methylphthalimide, N-carboxymethyl-3-nitrophthalimide) were evaluated in experimental models of acute and chronic inflammatory and neuropathic pain.

METHODS

The phthalimide analogues were administered per os (po) in Swiss mice or Wistar rats. Nociceptive response induced by formaldehyde and mechanical allodynia induced by chronic constriction injury (CCI) of the sciatic nerve or intraplantar (ipl) injection of complete Freund's adjuvant (CFA) were used as experimental models of pain.

RESULTS

N-carboxymethyl-3-nitrophthalimide (700 mg/kg, -1 h) inhibited the second phase of the nociceptive response induced by the intraplantar injection of formaldehyde in mice. N-3-hidroxypropylphthalimide (546 mg/kg, -1 h) inhibited both phases of the nociceptive response induced by formaldehyde. Treatment of rats with N-carboxymethyl-3-nitrophthalimide (700 mg/kg) or N-3-hydroxypropylphthalimide (546 mg/kg) inhibited the mechanical allodynia induced by CCI of the sciatic nerve or ipl injection of CFA in rats. Intraperitoneal administration of the opioid antagonist naltrexone (10 mg/kg, -1.5 h) attenuated the antinociceptive activity of N-carboxymethyl-3-nitrophthalimide (700 mg/kg) in the model of nociceptive response induced by formaldehyde.

CONCLUSIONS

N-3-hydroxypropylphthalimide and N-carboxymethyl-3-nitrophthalimide, two phthalimide analogues devoid of the glutarimide moiety, exhibited activities in different experimental models of pain, including models of chronic inflammatory and neuropathic pain.

Synthesis and cytotoxicity evaluation of glycosidic derivatives of lawsone against breast cancer cell lines

Breast cancer is the most incident and mortal cancer type in women, with an estimated 2 million new cases expected by 2020 worldwide, with 600,000 deaths. As not all breast cancer types respond to the anti-hormonal therapy, the development of new antineoplastic drugs is necessary. Lawsone (2-hydroxy-1,4-naphtoquinone) is a natural bioactive naphtoquinone displaying a range of activities, with dozens of derivatives described in the literature, including some glycosides possessing antitumor activity. Here, a series of glycosides of lawsone are reported for the first time and all compounds displayed good activity against the SKBR-3 cell line, with IC₅₀ below 10 µM. The most promising derivative was the glycosyl triazole derived from peracetylated d-glucose (11), which showed better cytotoxicity against SKBR-3 (IC₅₀ = 0.78 µM), being the most selective toward this tumoral cell (SI > 20). All compounds described in this work were more active than lawsone, indicating the importance of the carbohydrate and glycosyl triazole moiety for activity.

Antibacterial activity of synthetic 1,3-bis(aryloxy)propan-2-amines against Gram-positive bacteria

Synthetic 1,3‐bis(aryloxy)propan‐2‐amines have been shown in previous studies to possess several biological activities, such as antifungal and antiprotozoal. In the present study, we describe the antibacterial activity of new synthetic 1,3‐bis(aryloxy)propan‐2‐amines against Gram‐positive pathogens (Streptococcus pyogenes, Enterococcus faecalis and Staphylococcus aureus) including Methicillin–resistant S. aureus strains. Our compounds showed minimal inhibitory concentrations (MIC) in the range of 2.5–10 μg/ml (5.99–28.58 μM), against different bacterial strains. The minimal bactericidal concentrations found were similar to MIC, suggesting a bactericidal mechanism of action of these compounds. Furthermore, possible molecular targets were suggested by chemical similarity search followed by docking approaches. Our compounds are similar to known ligands targeting the cell division protein FtsZ, Quinolone resistance protein norA and the Enoyl‐[acyl‐carrier‐protein] reductase FabI. Taken together, our data show that synthetic 1,3‐bis(aryloxy)propan‐2‐amines are active against Gram‐positive bacteria, including multidrug–resistant strains and can be a promising lead in the development of new antibacterial compounds for the treatment of these infections.

Technetium-99m-labeled lapachol as an imaging probe for breast tumor identification

OBJECTIVE

Breast cancer is a health problem worldwide with high incidence and mortality rates. It is well known that the development of more sensitive and specific diagnostic methods is of great importance since an early diagnosis is essential to successfully treat tumors. Lapachol is a natural compound, belonging to the naphthoquinone group that has been widely used in traditional medicine to treat various illnesses, including cancer. The aim of this study was to evaluate technetium-99m (^99mTc) labeled lapachol as an imaging probe for breast cancer identification.

METHODS

To achieve this purpose, lapachol was labeled with ^99mTc, radiochemical purity and in vitro stability were determined. Blood clearance, in healthy mice, and biodistribution, in 4T1 tumor-bearing mice, were also evaluated.

RESULTS

Lapachol was successfully labeled with ^99mTc, with high values of radiochemical yield (95.9±3.4%). In vitro stability showed that the radiolabeled complex remained stable for up to 24h, with values above 90% for both saline and plasma (95.6±3.6% and 96.4±1.7%, respectively). The radiolabeled complex decays in a biphasic manner, with a half-life of distribution and elimination equal to 3.3 and 50.0min, respectively. Biodistribution and scintigraphic images showed high uptake in organs of excretion (kidneys, liver, and intestine). It could be also noted that tumor uptake was higher than the muscle at all time points. Tumor-to-muscle ratio reaches ∼4.5 at 24h after administration.

CONCLUSION

These findings suggest that ^99mTc-lapachol can be a potential diagnostic agent for breast tumors.

Biological and physicochemical properties of biosurfactants produced by Lactobacillus jensenii P6A and Lactobacillus gasseri P65

Background

Lactobacillus species produce biosurfactants that can contribute to the bacteria’s ability to prevent microbial infections associated with urogenital and gastrointestinal tracts and the skin. Here, we described the biological and physicochemical properties of biosurfactants produced by Lactobacillus jensenii P_6A and Lactobacillus gasseri P₆₅.

Results

The biosurfactants produced by L. jensenii P_6A and L. gasseri P₆₅ reduced the water surface tension from 72 to 43.2 mN m⁻¹ and 42.5 mN m⁻¹ as their concentration increased up to the critical micelle concentration (CMC) values of 7.1 and 8.58 mg mL⁻¹, respectively. Maximum emulsifying activity was obtained at concentrations of 1 and 5 mg mL⁻¹ for the P_6A and P₆₅ strains, respectively. The Fourier transform infrared spectroscopy data revealed that the biomolecules consist of a mixture of carbohydrates, lipids and proteins. The gas chromatography-mass spectrum analysis of L. jensenii P_6A biosurfactant showed a major peak for 14-methypentadecanoic acid, which was the main fatty acid present in the biomolecule; conversely, eicosanoic acid dominated the biosurfactant produced by L. gasseri P₆₅. Although both biosurfactants contain different percentages of the sugars galactose, glucose and ribose; rhamnose was only detected in the biomolecule produced by L. jensenii P_6A. Emulsifying activities were stable after a 60-min incubation at 100 °C, at pH 2–10, and after the addition of potassium chloride and sodium bicarbonate, but not in the presence of sodium chloride. The biomolecules showed antimicrobial activity against clinical isolates of Escherichia coli and Candida albicans, with MIC values of 16 µg mL⁻¹, and against Staphylococcus saprophyticus, Enterobacter aerogenes and Klebsiella pneumoniae at 128 µg mL⁻¹. The biosurfactants also disrupted preformed biofilms of microorganisms at varying concentrations, being more efficient against E. aerogenes (64%) (P_6A biosurfactant), and E. coli (46.4%) and S. saprophyticus (39%) (P₆₅ biosurfactant). Both strains of lactobacilli could also co-aggregate pathogens.

Conclusions

This report presents the first characterization of biosurfactants produced by L. jensenii P_6A and L. gasseri P₆₅. The antimicrobial properties and stability of these biomolecules indicate their potential use as alternative antimicrobial agents in the medical field for applications against pathogens that are responsible for infections in the gastrointestinal and urogenital tracts and the skin.

Production of the Cytotoxic Cardenolide Glucoevatromonoside by Semisynthesis and Biotransformation of Evatromonoside by a Digitalis lanata Cell Culture

Recent studies demonstrate that cardiac glycosides, known to inhibit Na⁺/K⁺-ATPase in humans, have increased susceptibility to cancer cells that can be used in tumor therapy. One of the most promising candidates identified so far is glucoevatromonoside, which can be isolated from the endangered species Digitalis mariana ssp. heywoodii. Due to its complex structure, glucoevatromonoside cannot be obtained economically by total chemical synthesis. Here we describe two methods for glucoevatromonoside production, both using evatromonoside obtained by chemical degradation of digitoxin as the precursor. 1) Catalyst-controlled, regioselective glycosylation of evatromonoside to glucoevatromonoside using 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide as the sugar donor and 2-aminoethyldiphenylborinate as the catalyst resulted in an overall 30 % yield. 2) Biotransformation of evatromonoside using Digitalis lanata plant cell suspension cultures was less efficient and resulted only in overall 18 % pure product. Structural proof of products has been provided by extensive NMR data. Glucoevatromonoside and its non-natural 1-3 linked isomer neo-glucoevatromonoside obtained by semisynthesis were evaluated against renal cell carcinoma and prostate cancer cell lines.

1,3-Bis(aryloxy)propan-2-ols as potential antileishmanial agents

We describe herein the synthesis and antileishmanial activity of 1,3‐bis(aryloxy)propan‐2‐ols. Five compounds (2, 3, 13, 17, and 18) exhibited an effective antileishmanial activity against stationary promastigote forms of Leishmania amazonensis (IC₅₀ < 15.0 μm), and an influence of compound lipophilicity on activity was suggested. Most of the compounds were poorly selective, as they showed toxicity toward murine macrophages, except 17 and 18, which presented good selective indexes (SI ≥ 10.0). The five more active compounds (2, 3, 13, 17, and 18) were selected for the treatment of infected macrophages, and all of them were able to reduce the number of internalized parasites by more than 80%, as well as the number of infected macrophages by more than 70% in at least one of the tested concentrations. Altogether, these results demonstrate the potential of these compounds as new hits of antileishmanial agents and open future possibilities for them to be tested in in vivo studies.

Glycotriazole-peptides derived from the peptide HSP1: synergistic effect of triazole and saccharide rings on the antifungal activity

This work proposes a strategy that uses solid-phase peptide synthesis associated with copper(I)-catalyzed azide alkyne cycloaddition reaction to promote the glycosylation of an antimicrobial peptide (HSP1) containing a carboxyamidated C-terminus (HSP1-NH₂). Two glycotriazole-peptides, namely [p-Glc-trz-G¹]HSP1-NH₂ and [p-GlcNAc-trz-G¹]HSP1-NH₂, were prepared using per-O-acetylated azide derivatives of glucose and N-acetylglucosamine in the presence of copper(II) sulfate pentahydrate (CuSO₄·5H₂O) and sodium ascorbate as a reducing agent. In order to investigate the synergistic action of the carbohydrate motif linked to the triazole-peptide structure, a triazole derivative [trz-G¹]HSP1-NH₂ was also prepared. A set of biophysical approaches such as DLS, Zeta Potential, SPR and carboxyfluorescein leakage from phospholipid vesicles confirmed higher membrane disruption and lytic activities as well as stronger peptide-LUVs interactions for the glycotriazole-peptides when compared to HSP1-NH₂ and to its triazole derivative, which is in accordance with the performed biological assays: whereas HSP1-NH₂ presents relatively low and [trz-G¹]HSP1-NH₂ just moderate fungicidal activity, the glycotriazole-peptides are significantly more effective antifungal agents. In addition, the glycotriazole-peptides and the triazole derivative present strong inhibition effects on ergosterol biosynthesis in Candida albicans, when compared to HSP1-NH₂ alone. In conclusion, the increased fungicidal activity of the glycotriazole-peptides seems to be the result of (A) more pronounced membrane-disruptive properties, which is related to the presence of a saccharide ring, together with (B) the inhibition of ergosterol biosynthesis, which seems to be related to the presence of both the monosaccharide and the triazole rings.

On the investigation of hybrid quinones: synthesis, electrochemical studies and evaluation of trypanocidal activity

Thirty-eight compounds were evaluated against T. cruzi and six were found to be more potent against trypomastigotes than benznidazole.

Synthesis of a novel series of 2,3,4-trisubstituted oxazolidines designed by isosteric replacement or rigidification of the structure and cytotoxic evaluation

Rigidification of the structure of 2,3,4-trisubstituted oxazolidines enhances the activity against LNCaP cells without affecting normal cell proliferation.

Effects of metronidazole analogues on Giardia lamblia: experimental infection and cell organization

The chemotherapeutic agents used for the treatment of giardiasis are often associated with adverse side effects and are refractory cases, due to the development of resistant parasites. Therefore the search for new drugs is required. We have previously reported the giardicidal effects of metronidazole (MTZ) and its analogues (MTZ-Ms, MTZ-Br, MTZ-N(3), and MTZ-I) on the trophozoites of Giardia lamblia. Now we evaluated the activity of some giardicidal MTZ analogues in experimental infections in gerbils and its effects on the morphology and ultrastructural organization of Giardia. The giardicidal activity in experimental infections showed ED(50) values significantly lower for MTZ-I and MTZ-Br when compared to MTZ. Transmission electron microscopy was employed to approach the mechanism(s) of action of MTZ analogues upon the protozoan. MTZ analogues were more active than MTZ in changing significantly the morphology and ultrastructure of the parasite. The analogues affected parasite cell vesicle trafficking, autophagy, and triggered differentiation into cysts. These results coupled with the excellent giardicidal activity and lower toxicity demonstrate that these nitroimidazole derivates may be important therapeutic alternatives for combating giardiasis. In addition, our results suggest a therapeutic advantage in obtaining synthetic metronidazole analogues for screening of activities against other infectious agents.

Synthesis and evaluation of D-gluconamides as green mineral scales

A series of 13 D-gluconamides were synthesized in moderate to good yields and evaluated as green scale inhibitors. The crystal structures of two compounds were determined by X-ray crystallography. The compounds 6c and 6d showed a reasonable inhibition of BaSO(4) precipitation from aqueous solution (47% and 51%, respectively) that indicated the potential for these derivatives of δ-gluconolactone.

Effect of metronidazole analogues on Giardia lamblia cultures

We comparatively evaluate the effect of metronidazole (MTZ) and its five analogues on trophozoites of Giardia lamblia axenically growing. The compounds MTZ-Ms, MTZ-I, MTZ-Br, MTZ-N(3), and MTZ-NH(3)Cl were obtained by molecular modification of the side chain of MTZ. Four of them presented higher giardicidal activity when compared with MTZ. Among them, MTZ-Br and MTZ-I were the most active, without cytotoxic effects against mitogen-activated human peripheral blood mononuclear cells (PBMC). The alteration of MTZ side chain constitutes a fruitful field to develop new drugs for the treatment not only of giardiasis but also of other diseases and signalize that metronidazole analogues are promising candidates as giardicidal and should be further evaluated.

Effect of the leaving group on the electrodic reduction mechanism of anti-Helicobacter pylori metronidazole derivatives, in aprotic and protic media

Because redox properties are central to bioreductive drug activity and selectivity, six 2-methyl-5-nitroimidazole, substituted at the N1-ethyl side chain with I, Br, Cl, OAc, OMs and NH(3)(+) were synthesized and submitted to cyclic voltammetry and electrolyses, in order to define their electrodic reduction mechanism, in aprotic [dimethylsulphoxide (DMSO)+0.1 mol l(-1) tetrabuthylammonium perchlorate (TBAP)] and phosphate-buffered media, on glassy carbon electrode, in comparison with metronidazole. Three of these compounds, namely, the iodo, bromo and ammonium salt derivatives showed significant anti-Helicobacter pylori (strain resistant to metronidazole) activity. All the cyclic voltammograms (CV), in aprotic medium, are similar to the one for metronidazole, except for -I, -Br and -NH(3)(+) derivatives. The CV of the N1-ethylhalide (-I, -Br) 5-nitroimidazole showed more intense and irreversible first waves, even at faster sweep rates (nu<2 V s(-1)). The absence of the first wave anodic counterpart, along with analysis of the dependence of E(p), I(p) and other parameters with nu, and results from electrolysis (consumption of two electrons) showed the process to be an ECE system, with halide release, after uptake of two electrons. This behaviour represents a case of dissociative electron transfer (ET). For the ammonium salt, self-protonation mechanism was evident. The facility of reduction represented by the first wave potential and concerning the substituents is NH(3)(+)>Br>I>Cl>OMs>OH>OAc. In aqueous phosphate-buffered medium, the electrochemical behaviour of all the compounds is similar to the one of metronidazole, represented by a unique and irreversible 4e(-)/4H(+) wave. The order of reduction ease is NH(3)(+)>Br approximately OMs>I>OH>OAc. Aprotic medium allows a better discrimination between the substituents. Concerning biological activity, despite the impossibility of establishing a correlation, it has been observed that the more electrophilic compounds showed better anti-H. pylori activity.

In vitro evaluation of the activity of aromatic nitrocompounds against Trypanosoma cruzi

Fourteen compounds were evaluated for their activity against Trypanosoma cruzi blood stream forms at the concentration of 500 g/ml. Six compounds were active and re-tested at lower concentrations.

Potential use of WR6026 as prophylaxis against transfusion-transmitted American trypanosomiasis

Since transmission of Chagas' disease by the insect vector is under control in Brazil, transmission by blood transfusion is acquiring special relevance in areas where the disease is endemic and also in countries whose populations are free of infection but that are receiving immigrants from areas where the disease is endemic. Gentian violet, a phenylmethane dye, was the first agent used for the chemical prophylaxis of blood destined for transfusion. A concentration of 0.6 mmol of this dye per liter is effective at eliminating trypomastigotes from blood after 24 h of incubation at 4 degrees C. It is the only effective trypanosomicidal agent available. In the search of alternate compounds, we examined a number of synthetic compounds. They were screened for their activities against blood trypomastigotes of the Y, CL, and B229 strains of Trypanosoma cruzi by using two or more dilutions of each compound. We found that compound Q45, a 6-methoxy-8(diethylaminohexylamino)lepidine dihydrochloride, was highly effective at clearing parasites from infected blood. Doses of 65 and 130 micrograms of this compound eliminated trypomastigotes from blood experimentally contaminated with T. cruzi parasites. These results indicate that Q45 is remarkably active against circulating trypomastigotes. Further studies evaluating Q45 as a prophylactic agent for preventing the transmission of T. cruzi by blood transfusion are of interest.