Renata Barbosa de Oliveira

Synthesis of a sugar-based thiosemicarbazone series and structure-activity relationship versus the parasite cysteine proteases: rhodesain, cruzain and Schistosoma mansoni cathepsin B1

ABSTRACT The pressing need for better drugs against Chagas disease, African sleeping sickness, and schistosomiasis motivates the search for inhibitors of cruzain, rhodesain, and Schistosoma mansoni CB1 (SmCB1), the major cysteine proteases from Trypanosoma cruzi, Trypanosoma brucei, and S. mansoni, respectively. Thiosemicarbazones and heterocyclic analogues have been shown to be both antitrypanocidal and inhibitory against parasite cysteine proteases. A series of compounds was synthesized and evaluated against cruzain, rhodesain, and SmCB1 through biochemical assays to determine their potency and structure-activity relationships (SAR). This approach led to the discovery of 6 rhodesain, 4 cruzain, and 5 SmCB1 inhibitors with 50% inhibitory concentrations (IC50s) of ≤10 μM. Among the compounds tested, the thiosemicarbazone derivative of peracetylated galactoside (compound 4i) was discovered to be a potent rhodesain inhibitor (IC50 = 1.2 ± 1.0 μM). The impact of a range of modifications was determined; removal of thiosemicarbazone or its replacement by semicarbazone resulted in virtually inactive compounds, and modifications in the sugar also diminished potency. Compounds were also evaluated in vitro against the parasites T. cruzi, T. brucei, and S. mansoni, revealing active compounds among this series.

Agentes antineoplásicos biorredutíveis: uma nova alternativa para o tratamento de tumores sólidos

A problem often encountered in cancer therapy is the presence of tumor cell subpopulation that are resistant to treatment. Solid tumors frequently contain hypoxic cells that are resistant to killing by ionizing radiation and also by many chemotherapeutic agents. However, these hypoxic cells can be exploited for therapy by non-toxic hypoxic-activated prodrugs. Bioreductive drugs require metabolic reduction to generate cytotoxic metabolites. This process is facilitated by appropriate reductases and the lower oxygen conditions present in solid tumors. The unique presence of hypoxic cells in human tumors provides an important target for selective cancer therapy.

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.

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.

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.

Thiazole compounds with activity against Cryptococcus gattii and Cryptococcus neoformans in vitro.

Human cryptococcosis can occur as a primary or opportunistic infection and develop as an acute, subacute, or chronic, systemic infection involving different host organs. We evaluated the antifungal activity of thirteen compounds against Cryptococcus gattii and Cryptococcus neoformans in vitro, by assessing the toxicity of the compounds showing the greatest antifungal activity in VERO cells and murine macrophages. From these results, four compounds were considered promising for further studies because they displayed low cytotoxicity and significant antifungal activity. The heterocyclic compounds 1b, 1c, 1d, and 1m have antifungal activity levels between that of amphotericin B and fluconazole in vitro. The death curve of Cryptococcus spp. treated with these four compounds was similar to the curve obtained for amphotericin B, in that we observed a significant reduction in cell viability within the first 24 h of treatment. Additionally, we found that there was no effect when these compounds were combined with amphotericin and fluconazole, except for 1c, which antagonized the effect of amphotericin B against C. gattii, also reflected in the reduction of the post-antifungal effect (PAFE); however, this interaction did not alter the ergosterol content. The results shown in this paper reveal the discovery of novel thiazole compounds, which are easy to synthesize, and with potentially exhibit antifungal activity, and display low cytotoxicity in normal mammalian cells. These compounds can be used as prototypes for the design of new antifungal drugs against C. gattii and C. neoformans.

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 in Vitro Cytotoxic Activity of Compounds with Pro-Apoptotic Potential

In our search for new anticancer therapies, some compounds synthesized in our lab were selected and their potential cytotoxic activity was evaluated in vitro against two cancer cells lines including a solid tumor (UACC-62, melanoma) and a human lymphoma (JURKAT). Compounds showing cytotoxic activity were subjected to an apoptosis assay. Two compounds showed promising results.

Synthesis of Nitroaromatic Compounds as Potential Anticancer Agents

Twenty-seven nitrated and non-nitrated compounds have been synthesized and tested for their growth inhibitory activity on three human cancer cells lines. Fourteen compounds were able to inhibit more than 50% of the growth of at least one of the cancer cell lines and five compounds exhibited high antiproliferative activity on human cancer cell lines (IC50 < 8.5 μM). The cytotoxicity of the compounds on Vero cell line was established in vitro to evaluate the selectivity. All active compounds have a good leaving group (bromide or chloride) at the benzylic position, indicating that the mechanism of action of these compounds is related to their alkylating properties. Two compounds (3 and 24) were selected for further studies in mice with Ehrlich solid tumors and display significant antitumor effects in vivo.

The activity of a metronidazole analogue and its β-cyclodextrin complex against Trypanosoma cruzi

In this study we prepared an inclusion complex between an iodide analogue of metronidazole (MTZ-I) and cyclodextrin (CD) to develop a safer and more effective method of treating Trypanosoma cruzi infections. According to our results, MTZ-I and MTZ-I:β-CD were 10 times more active than MTZ, demonstrating that the presence of an iodine atom on the side chain increased the trypanocidal activity while maintaining its cytotoxicity. The selective index shows that MTZ-I was 10 times more active against T. cruzi than it was against mammalian cells. The modification of MTZ side chains provides a promising avenue for the development of new drugs.