André Luis Almeida Souza

Synthesis, characterization and biological activities of 3-aryl-1,4-naphthoquinones – green palladium-catalysed Suzuki cross coupling

Quinones are important scaffolds that are present in a variety of natural products or synthetic bioactive molecules. Arylation is an important strategy for accomplishing structural modifications, leading to new potential candidates for use as drugs. In the present work, palladium-catalysed, ligandless and phosphine-free Suzuki coupling reactions between 2-hydroxy-3-iodo-1,4-naphthoquinone and boronic acids were employed to prepare several 2-hydroxy-3-aryl-1,4-naphthoquinones in aqueous conditions using microwave irradiation or conventional heating. Because of the biological activities of quinones, which are related to their ability to accept electrons to form semiquinones and hydroquinones, the electrochemical behaviour of the synthesized molecules was investigated. The Osiris and Molinspiration Cheminformatics programs, utilizing in silico analyses, imply that these naphthoquinones are candidates for use as drugs which was reinforced by the outcomes of the in vitro antifungal and trypanocidal activity tests. Our in vitro data indicated a MIC value of 8 μg mL−1 against Candida albicans ATCC 24433 strains, and an EC50 of 0.67 μM with respect to trypanocidal activity against Trypanosoma cruzi epimastigote strains (Y).

Temporizin and Temporizin-1 Peptides as Novel Candidates for Eliminating Trypanosoma cruzi

Tropical diseases caused by parasitic infections continue to cause socioeconomic distress worldwide. Among these, Chagas disease has become a great concern because of globalization. Caused by Trypanosoma cruzi, there is an increasing need to discover new, more effective methods to manage infections that minimize disease onset. Antimicrobial peptides represent a possible solution to this challenge. As effector molecules of the innate immune response against pathogens, they are the first line of defense found in all multi-cellular organisms. In amphibians, temporins are a large family of antimicrobial peptides found in skin secretions. Their functional roles and modes of action present unique properties that indicate possible candidates for therapeutic applications. Here, we investigated the trypanocide activity of temporizin and temporizin-1. Temporizin is an artificial, hybrid peptide containing the N-terminal region of temporin A, the pore-forming region of gramicidin and a C-terminus consisting of alternating leucine and lysine. Temporizin-1 is a modification of temporizin with a reduction in the region responsible for insertion into membranes. Their activities were evaluated in a cell permeabilization assay by flow cytometry, an LDH release assay, electron microscopy, an MTT assay and patch clamp experiments. Both temporizin and temporizin-1 demonstrated toxicity against T. cruzi with temporizin displaying slightly more potency. At concentrations up to 100 μg/ ml, both peptides exhibited low toxicity in J774 cells, a macrophage lineage cell line, and no toxicity was observed in mouse primary peritoneal macrophages. In contrast, the peptides showed some toxicity in rat adenoma GH3 cells and Jurkat human lymphoma cells with temporizin-1 displaying lower toxicity. In summary, a shortened form of the hybrid temporizin peptide, temporizin-1, was efficient at killing T. cruzi and it has low toxicity in wild-type mammalian cells. These data suggest that temporizin-1 might be a candidate for Chagas disease therapy.

Development of an electrochemical immunosensor for the diagnostic testing of spotted fever using synthetic peptides

Spotted fever is a rare acute and multisystemic febrile infectious disease with a mortality rate of ≥50% without adequate antibiotic treatment, and in diagnosed and treated cases, of approximately 2.5%. Currently, the applied test to diagnose this disease is the indirect immunofluorescence reaction, however two samples of paired sera are necessary to confirm the diagnosis, since using only one sample may allow for confusion with cross reactions. OmpA is an outer membrane protein present in the R. rickettsia, the etiological agent of spotted fever, able to activate dendritic and macrophage cells. It also presents immunogenicity properties, and is considered a target for the development of diagnostic tests for spotted fever. In this context, an amperometric immunosensor was developed for the identification of sera antibodies (human IgG) from patients with spotted fever aimed at improving sensitivity and minimize sample volume. The development of the immunosensor was conducted using a synthetic peptide, derivative from the H6PGA4 R. rickettsia protein, homologous to OmpA. Amperometric responses were generated at -0.6 to 0.6V, at a scan rate of 0.025Vs-1 for 20 cycles, a limit of detection of approximately 10ngmL-1 for the synthetic peptides and 0.01µgmL-1 for the humam serum, a sensitivity of 2.59µA, adequate for the detection of spotted fever antibodies. The construction of this immunosensor, capable of identifying circulating antibodies in real time, can also be applied in the diagnosis of other infectious-parasitic diseases.

Development of an elisa for the diagnosis of reactive IgE antibodies anti-therapeutic horse sera

&NA; Hypersensitive diseases that involve IgE reactivity are important concern of public, especially those encompassing the potential pathogenesis from the administration of horse serum‐based therapeutics such as antivenoms. A method for the definitive diagnosis of reactive IgE is important for identifying allergic patients to control severe collateral effects during planned and emergency application of immunotherapies when the allergy source cannot be avoided for treatment. To date, no tests have been developed to accompany the wide range of antivenoms produced from horse sera. The aim of this was to develop a cost‐effective ELISA of high sensitivity and specificity to detect circulating patient IgE that binds horse IgG3, the most prevalent antibody class in passive antibody therapies. Horse IgG3 was purified in a single step on jacalin‐Sepharose and absorbed to standard ELISA plates as the capture molecule for reactive human IgE. The direct performance evaluation with allergenic and non‐allergenic patient, together with competitive peptides assays, showed high sensitivity and specificity to detect human IgE that recognized horse IgG3. The analytical sensitivity and ED50 were calculated to be 0.01 &mgr;g mL−1 and 0.052 &mgr;g mL−1, respectively. The intra‐ and inter‐assay coefficient of variation ranged from 3.3 to 11.1% and 4.0–8.0%, respectively. The horse IgG3‐based ELISA assay can detect reactive allergenic IgE at picomolar concentrations. The coefficient of variation suggests that it can be easily standardized between laboratories, provide rapid and can be applied to population surveillance. Patient management during treatment for envenomation would be greatly improved by a robust and reliable diagnostic test for preexisting allergies to mitigate life‐threating consequences of hypersensitivity. HighlightsAllergy diseases mediated by patient IgE are an important public healthcare concern.An ID‐ELISA was developed to detect human IgE reactive to horse IgG3.The sensitivity and ED50 was 0.01 &mgr;g mL−1 and 0.052 &mgr;g mL−1, respectively.The intra‐ and inter‐assay coefficient of variation ranged from 3.31 to 11.12% and 3.99–8.01%, respectively.

Searching for new drugs for Chagas diseases: triazole analogs display high in vitro activity against Trypanosoma cruzi and low toxicity toward mammalian cells

Chagas disease is one of the most relevant endemic diseases in Latin America caused by the flagellate protozoan Trypanosoma cruzi. Nifurtimox and benzonidazole are the drugs used in the treatment of this disease, but they commonly are toxic and present severe side effects. New effective molecules, without collateral effects, has promoted the investigation to develop new lead compounds with to advance for clinical trials. Previously, 3-nitro-1H-1,2,4-triazole-based amines and 1,2,3-triazoles demonstrated significant trypanocidal activity against T. cruzi. In this paper, we synthesized a new series of 92 examples of 1,2,3-triazoles. Six compounds exhibited antiparasitic activity, 14, 25, 27, 31 and 40, 43 and were effective against epimastigotes of two strains of T. cruzi (Y and Dm28-C) and 25, 27 and 31 exhibited trypanocidal activity similar to benzonidazole. Notably, the compound 25 compared to benzonidazole increase the toxicity against T. cruzi, with no apparent toxicity to the cell line of mice macrophages or primary mice peritoneal macrophages. As results, we calculated selectivity indexes up to 2000 to 25 and 31 in both T. cruzi strains. Derivative 14 caused a trypanostatic effect because it did not damage external epimastigote membrane. Triazoles 40 and 43 impaired parasites viability using a pathway not dependent on ROS production.

Bactericidal Activity of a Cationic Peptide on Neisseria meningitidis

The increasing prevalence of antibiotic resistance has formed an urgent need for substitute drugs with new mechanisms of action. Antimicrobial peptides (AMPs) are promising candidates that could address the meal of multidrug-resistant bacteria. Neisseria meningitidis represents a pathogen of great public health importance in both developed and developing countries and is intrinsically highly resistant to some AMPs, such as polymyxin B. In this work, a cationic 11-residue peptide named of poly-Leu (KLKLLLLLKLK) was synthesized and its antimeningococcal activity availed and compared with cecropin A and the poly-P (KLKPPPPPKLK) by flow cytometry, electron microscopy and measurement of the periplasmatic enzyme alkaline phosphatase activity. Live N. meningitidis serotype B cells were grown with different concentrations of the peptides and after washing propidium iodide was added and the optical density measured at 600 nm. N. meningitidis cells containing 10 µg/106 cells of the poly-Leu peptide presented 90,3% uptake of the dye (EC50 value of 7.9 µg mL-1). The uptake of the dye by control cells not incubated with the poly-Leu peptide or with an identical concentration of cecropin and poly-Pro peptides was lesser than 10%. The susceptibility of the N. meningitidis serotype B to the cationic peptide poly-Leu was also demonstrated by electron microscopy analysis. The damage increased with the increase of the peptide concentration and a slicing and peels effect of the cellular wall and apparent injury of the internal membrane. The damage to the external membrane was confirmed through the measurement of the alkaline phosphatase.

Synthesis and Evaluation of the Anticancer and Trypanocidal Activities of Boronic Tyrphostins

Molecules containing an (cyanovinyl)arene moiety are known as tyrphostins because of their ability to inhibit proteins from the tyrosine kinase family, an interesting target for the development of anticancer and trypanocidal drugs. In the present work, (E)‐(cyanovinyl)benzeneboronic acids were synthesized by Knoevenagel condensations without the use of any catalysts in water through a simple protocol that completely avoided the use of organic solvents in the synthesis and workup process. The in vitro anticancer and trypanocidal activities of the synthesized boronic acids were also evaluated, and it was discovered that the introduction of the boronic acid functionality improved the activity of the boronic tyrphostins. In silico target fishing with the use of a chemogenomic approach suggested that tyrosine‐phosphorylation‐regulated kinase 1a (DYRK1A) was a potential target for some of the designed compounds.

Correction to: Cryptosporidium Spp. Contamination in Perna perna Mussels Destined for Human Consumption in Southeastern Rio de Janeiro, Brazil

The original version of this article unfortunately contained a mistake.

Electrochemical immunosensor for differential diagnostic of Wuchereria bancrofti using a synthetic peptide

Lymphatic filariasis (LF) is a neglected tropical disease transmitted by mosquitoes and the second cause of permanent disability leading to a significant morbidity and mortality rate. Previously, we have identified epitopes of the filarial abundant larval transcript-2 (ALT-2) protein using a microarray mapping. In this study, one of the epitopes (Wb/ALT2-A5) was used to construct an electrochemical immunosensor. Electrochemical technique of cyclic voltammetry was performed for detecting the signal generated by the interaction between the (Wb/ALT2-A5) peptide and circulating antibodies of serum human samples. (Wb/ALT2-A5) epitope antigens were successfully immobilized on the working electrode of a screen-printed carbon electrode (SPCE) by their amine groups via chitosan film by coupling with glutaraldehyde as crosslinker. After the sensor ready, a pool of human sera infected with Wuchereria bancrofti was added to its surface. Electrochemical responses were generated by applying a potential of - 0.6 to 0.6 V, scan rate of 0.025 V/s. A detection limit of 5.0 µg mL-1 for the synthetic peptides (Wb/ALT2-A5) and 0.002 µg mL-1 for human serum, with a sensitivity of 1.86 µA. The performance of this assay was successfully tested in human serum samples from infected and healthy patients. Thus, this proposed immunosensor, which is able to identify circulating antibodies, can be applied to the diagnosis of the W. bancrofti parasitic disease.

Plants of Brazilian restingas with tripanocide activity against Trypanosoma cruzi strains

Chagas disease is caused by the Trypanosoma cruzi affecting millions of people, and widespread throughout Latin America. This disease exhibits a problematic chemotherapy. Benznidazole, which is the drug currently used as standard treatment, lamentably evokes several adverse reactions. Among other options, natural products have been tested to discover a novel therapeutic drug for this disease. A lot of plants from the Brazilian flora did not contain studies about their biological effects. Restinga de Jurubatiba from Brazil is a sandbank ecosystem poorly studied in relation to plant biological activity. Thus, three plant species from Restinga de Jurubatiba were tested against in vitro antiprotozoal activity. Among six extracts obtained from leaves and stem parts and 2 essential oils derived from leave parts, only 3 extracts inhibited epimastigote proliferation. Substances present in the extracts with activity were isolated (quercetin, myricetin, and ursolic acid), and evaluated in relation to antiprotozoal activity against epimastigote Y and Dm28 Trypanosoma cruzi strains. All isolated substances were effective to reduce protozoal proliferation. Essentially, quercetin and myricetin did not cause mammalian cell toxicity. In summary, myricetin and quercetin molecule can be used as a scaffold to develop new effective drugs against Chagas’s disease.