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.

Preparation, characterization, and topical delivery of paromomycin ion pairing.

Topical chemotherapy with paromomycin (PA) has been used as an alternative for the treatment of cutaneous leishmaniasis; however, poor skin penetration of this drug limits the efficacy of formulations. The objective of this work was to study the ability of the PA free base to form ion pairing with organic acids, as well as evaluate the effect of these compounds on the topical delivery of PA. PA permeation across intact skin was low, while drug penetration into skin from PA ion pairing was the higher than that observed for the PA base. Data obtained on the stripped skin, a damaged skin model, clearly showed that the ion pairing presented a potential to improve PA skin permeation.

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.

Preparation and characterization of solid dispersion of simvastatin.

CONTEXT: Simvastatin (SIM), a widely used drug for the treatment of hypercholesterolemia, is a crystalline substance and practically insoluble in water. Its low dissolution rate leads to a poor absorption, distribution, and target organ delivery because the bioavailability of drugs with low aqueous solubility is limited by their dissolution rates. OBJECTIVE: The aim of this study was to prepare solid dispersions (SD) of SIM with inert carriers in an attempt to improve the release profile. METHODS: In this work, SIM SD with polyethylene glycol (PEG 6000) or polyvinylpyrrolidone (PVP K15) in 1:1, 1:2, 1: 3, 1:4, and 1:5 ratios were prepared and their stability and dissolution properties were investigated. SD were characterized by differential scanning calorimetry and X-ray powder diffraction. Tablets containing SD SIM : PEG 6000 were developed and their dissolution profile evaluated. RESULTS: Drug release from all SD was significantly improved when compared to their corresponding physical mixture or SIM alone. SD SIM:PVP showed drug degradation. The tablets gradually released SIM with a final quantity greater than 80% in 60 minutes. CONCLUSIONS: The preparation of SIM SD with PEG or PVP is a promising strategy to improve the bioavailability of the drug. SIM SD with PEG are more advantageous over the dispersions prepared with PVP because they do not show drug degradation during preparation.

Antifungal Activity Directed Toward the Cell Wall by 2-Cyclohexylidenhydrazo- 4-Phenyl-Thiazole Against Candida albicans.

BACKGROUND: The increasing incidence of invasive forms of candidiasis and resistance to antifungal therapy leads us to seek new and more effective antifungal compounds. OBJECTIVE: To investigate the antifungal activity and toxicity as well as to evaluate the potential targets of 2- cyclohexylidenhydrazo-4-phenyl-thiazole (CPT) in Candida albicans. METHODS: The antifungal activity of CPT against the survival of C. albicans was investigated in Caenorhabditis elegans. Additionally, we determined the effect of CPT on the inhibition of C. albicans adhesion capacity to buccal epithelial cells (BECs), the toxicity of CPT in mammalian cells, and the potential targets of CPT in C. albicans. RESULTS: CPT exhibited a minimum inhibitory concentration (MIC) value of 0.4-1.9 µg/mL. Furthermore, CPT at high concentrations (>60 x MIC) showed no or low toxicity in HepG2 cells and <1% haemolysis in human erythrocytes. In addition, CPT decreased the adhesion capacity of yeasts to the BECs and prolonged the survival of C. elegans infected with C. albicans. Analysis of CPT-treated cells showed that their cell wall was thinner than that of untreated cells, especially the glucan layer. We found that there was a significantly lower quantity of 1,3-ß-D-glucan present in CPT-treated cells than that in untreated cells. Assays performed on several mutant strains showed that the MIC value of CPT was high for its antifungal activity on yeasts with defective 1,3-ß-glucan synthase. CONCLUSION: In conclusion, CPT appears to target the cell wall of C. albicans, exhibits low toxicity in mammalian cells, and prolongs the survival of C. elegans infected with C. albicans.

Synthesis and antimalarial activity of semicarbazone and thiosemicarbazone derivatives.

Seventeen semicarbazone and thiosemicarbazone derivatives were prepared and tested in vitro against a chloroquine resistant strain of Plasmodium falciparum (W2) to evaluate their antiplasmodial potential. Three thiosemicarbazones were found to be active against the parasite and non-toxic to human peripheral blood mononuclear cells (PBMC). Among these, compound 5b presented the lowest IC50 value against P. falciparum (7.2 microM) and was the least toxic in the PBMC proliferation assay (IC50=73.5 microM). It was selected for in vivo tests on mice infected with Plasmodium berghei (strain NK-65). The thiosemicarbazone 5b was able to reduce the parasitaemia by 61% at 20 mg/kg on day 7 after infection without any sign of toxicity to the animals. In comparison, the standard drug chloroquine at 15 mg/kg showed a reduction around 95%. These in vitro and in vivo results make 5b an interesting lead for further development.

Synthesis and evaluation of cytotoxic activity of arylfurans.

A series of 2-aryl and 2,5-diarylfurans were synthesized and evaluated for their in vitro cytotoxicity against human cancer cells lines and on the proliferation of human peripheral blood mononuclear cells (PBMC) stimulated with phytohemaglutinin (PHA). Three compounds were found to present significant activity against the cancer cell lines without affecting the lymphocyte proliferation in PBMCs, indicating low toxicity to normal cells.

Synthesis and evaluation of the antiparasitic activity of bis-(arylmethylidene) cycloalkanones.

A series of bis-(arylmethylidene)-cycloalkanones was synthesized by cross-aldol condensation. The activity of the compounds was evaluated against amastigotes forms of Trypanosoma cruzi and promastigotes forms of Leishmania amazonensis. The cytotoxicity of the active compounds on uninfected fibroblasts or macrophages was established in vitro to evaluate the selectivity of their antiparasitic effects. Six compounds displayed trypanocidal activity against amastigotes intracellular forms of T. cruzi with IC50 values ranging from 7.0 to 249 µM. Besides these six compounds, eight other molecules exhibited significant leishmanicidal activity (IC50 values ranging from 0.6 to 110.4 µM). Two compounds can be considered as promising antiparasitic lead molecules because they showed IC50 values in the low-micromolar range (≤1.2 µM) with an adequate SI (≥19.9). To understand the mechanism of action of these compounds, two possible molecular targets were investigated: trypanothione reductase (TR) and cruzain.

Development and validation of a simple and fast HPLC method for determination of lovastatin, pravastatin and simvastatin.

Statins are effective and often-prescribed drugs for the treatment of hypercholesterolemia. This study shows a simple and fast method validation by reversed-phase high-performance liquid chromatography in the linear range 28 to 52 µg/mL to quantify lovastatin, pravastatin sodium or simvastatin in bulk drug or dosage forms. Statins were determined using a C8 endcapped column (250 × 4 mm, 5 µm), isocratic mobile phase of acetonitrile and 0.1% phosphoric acid (65:35), 30°C, ultraviolet-diode array detection at λ 238 nm and 1.5 mL/min flow for lovastatin and simvastatin and 1.0 mL/min for pravastatin sodium. The developed method is fast, simple, reliable and shows appropriate linearity (r > 0.999), accuracy (98.8-101.6%), precision (relative standard deviation <2%) and selectivity toward placebo and/or degradation products in very similar chromatographic conditions for all statins.

Synthesis and evaluation of the anti parasitic activity of aromatic nitro compounds.

A series of nitroaromatic compounds was synthesized and evaluated as potential antileishmanial and trypanocidal agents. Five compounds exerted significant anti-leishmanial activity in vitro against promastigotes forms of Leishmania (L.) amazonensis, with IC(50) in the range of 23-59 µmol L(-1), but none were active against amastigotes intracellular forms of Trypanosoma cruzi. In vitro cytotoxicity on the proliferation of human peripheral blood mononuclear cells (PBMC) stimulated with phytohemaglutinin (PHA) was also evaluated. Two compounds, 6 and 7, were found to present a promising anti-leishmanial activity with IC(50) values of 59.5 and 50.6 µM, respectively, without affecting the lymphocyte proliferation in PBMCs (selectivity index of 16.1 and 21.7, respectively), indicating low toxicity to human cells.

Arylfurans as potential trypanosoma cruzi trypanothione reductase inhibitors.

The natural lignans veraguensin and grandisin have been reported to be active against Trypanosoma cruzi bloodstream forms. Aiming at the total synthesis of these and related compounds, we prepared three 2-arylfurans and eight 2,5-diarylfurans. They were evaluated for their potential as T. cruzi trypanothione reductase (TR) inhibitors as well against the parasite's intracellular (amastigote) and bloodstream (trypomastigote) forms. Compound 12 was the most effective against TR with an IC50 of 48.5 microM while 7 and 14 were active against amastigotes, inhibiting the parasite development by 60% at 20 microg/ml (59 and 90 microM, respectively). On the other hand, none of the compounds was significantly active against the parasite bloodstream forms even at 250 microg/ml (0.6-1.5 mM).