Nitrofurazone and its nitroheterocyclic analogues: a study of the electrochemical behavior in aqueous medium

The biological action of drugs with potential antichagasic activities can be better understood by knowing their reduction mechanism. For this proposal, the electrochemical reduction of nitrofurazone (NF) and its analogues, nitrofurfurilidene thiosemicarbazone (NFS), nitrothiophene semicarbazone (NT), nitrothiophene thiosemicarbazone (NTS), was studied by differential pulse and cyclic voltammetries and chronoamperometry in aqueous medium by using a glassy carbon electrode. Those three synthetic analogues have oxygen and sulfur atoms arranged between the nitroheterocyclic ring (furan and thiophene, respectively) and the carbonyl group (semicarbazone and thiosemicarbazone, respectively). The respective hydroxylamine derivatives are the main products formed in acidic medium, being its formation linearly pH dependent. Although chronoamperometric data show that this reduction involves 4 electrons, its corresponding reduction voltammetric wave, in alkaline medium, is unfolded and a reversible reduction peak at a more positive potential appears. This peak is characterized as a nitro anion radical formation, whose decay is caused by a disproportionation reaction. Its kinetic stability was studied by the current ratio values of the R - NO2/R - NO2•- redox couple and the second-order constant (k2) was determined, being NTS the analogue that registered the highest stability.A compreensão do mecanismo de redução de compostos com potencial atividade antichagásica pode contribuir para o melhor entendimento de sua ação biológica. Com este objetivo, a redução eletroquímica de nitrofural (nitrofurazona, NF) e seus análogos, nitrofurfurilideno tiossemicarbazona (NFS), nitrotiofeno semicarbazona (NT), nitrotiofeno tiossemicarbazona (NTS), foi estudada pelas voltametrias de pulso diferencial, cíclica e cronoamperometria em meio aquoso, utilizando eletrodo de carbono vítreo. Esses três análogos sintéticos apresentam átomos de oxigênio e de enxofre distribuídos no anel heterocíclico (furano e tiofeno, respectivamente) e no grupo carbonila (semicarbazona e tiossemicarbazona, respectivamente). A hidroxilamina é o principal produto formado em meio ácido, sendo sua formação linearmente dependente do pH. A cronoamperometria mostrou que esta redução envolve 4 elétrons. Entretanto, em meio alcalino, esta onda de redução é desdobrada e um pico reversível a potencial mais positivo foi registrado, correspondendo à formação nitro ânion radical. O nitro ânion radical sofre desproporcionamento e sua estabilidade cinética foi avaliada aplicando a razão de corrente correspondente ao par reversível R - NO2/R - NO2•- e as constantes de segunda ordem (k2) foram determinadas. A partir dos valores de k2 observou-se que o análogo NTS registrou a maior estabilidade.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade de São Paulo Faculdade de Ciências Farmacêuticas Departmento de FarmáciaUniversidade Federal de São Paulo (UNIFESP) Departmento de Ciências Exatas e da TerraUNIFESP, Departmento de Ciências Exatas e da TerraProc. 2011/11499-0SciEL

Potential antichagasic: the rational pursuit of compounds with selective action by cruzain

A doença de Chagas, parasitose endêmica causada pelo Trypanosoma cruzi, se apresenta como grande causa de morbimortalidade, afetando cerca de 18 milhões de pessoas no continente americano e causando 21.000 mortes, a cada ano. Atualmente, estima-se que 100 milhões de pessoas estejam sob risco de contaminação nos 18 países da área endêmica da doença. A quimioterapia contra a tripanossomíase americana é constituída por apenas dois fármacos, nifurtimox e benznidazol, que não apresentam ação adequada na fase crônica da doença. Por estas razões, é premente a necessidade de novas e mais eficazes alternativas terapêuticas. A cruzaína, mais abundante cisteíno-protease do parasita, é enzima essencial em todos os estágios de modificação celular do parasita e está, também, presente no processo de invasão e modificação do sistema imune do hospedeiro. Além disso, apresenta diferenças em relação a enzimas dessa categoria no hospedeiro. Trata-se, pois, de excelente alvo bioquímico para a pesquisa de novos agentes contra o T. cruzi. Face ao exposto e tendo-se em vista a especificidade da cruzaína, considera-se de grande interesse a compreensão do mecanismo de interação de compostos com essa enzima com o intuito de planejar derivados com atividade antichagásica potencial. O presente trabalho teve o objetivo de elucidar a afinidade de diferentes classes de compostos pela enzima, na busca racional de novos tripanomicidas. Assim, pró-fármacos peptídicos recíprocos, derivados de primaquina(PQ) e de nitrofural(NF), anteriormente sintetizados, e pró-fármacos peptídicos duplos do hidroximetilnitrofural (NFOH) planejados, e cuja síntese foi estudada, foram submetidos a estudos de modelagem molecular e de docking. Os peptídios foram escolhidos com base na cisão específica pelacruzaína. Avaliou-se a interação com a enzima e elucidar o mecanismo de liberação dos fármacos e composto ativo a partir desses derivados. Os estudos indicaram que o melhor transportador a ser utilizado no planejamento de novos pró-fármacos é o dipeptídio LysArg, corroborando o que havia sido observado nos ensaios em cultura de células infectadas . com o T. cruzi. Ante a possibilidade de um segundo mecanismo de ação pela interação entre a Cys25 da cruzaína e o grupo semicarbazona, presente no NF e no NFOH, planejaram-se e sintetizaram-se análogos destes compostos, utilizando bioisosterismo clássico entre enxofre e oxigênio. Estudos de modelagem molecular e docking indicaram a participação também deste mecanismo de ação na atividade dos referidos derivados nitro-heterocíclicos. Todos os bioisósteros apresentaram ação inibitória na cruzaína IC50 entre 2,71 µM e 22,83 µM - evidenciando, também, este mecanismo de ação. Com o objetivo de se estudar a influência do grupamento (tio)semicarbazona presente nos derivados bioisostéricos sintetizados, realizaram-se estudos de QSAR 20 e 3D em série de compostos descritos na literatura, obtendo-se modelos robustos e com grau elevado de predição, comprovando a ação na cruzaína. Tais grupos podem ser utilizados no planejamento de novos tripanomicidas. Complementando a busca racional de novos antichagásicos potenciais, efetuou-se triagem virtual de novos ligantes utilizando o planejamento racional com base na estrutura do receptor (SBDD) a partir de modelo farmacofórico específico obtido para a cruzaína. Esse estudo proporcionou a sugestão de vinte moléculas a partir do banco de dados CHEMDIV, com possível ação inibitória da enzima. Com base nos resultados obtidos, conclui-se que os estudos realizados com pró-fármacos e análogos por meio de processos racionais de planejamento forneceram dados importantes para a pesquisa de candidatos a novos fármacos antichagásicos.Chagas \' disease, a parasitosis caused by Trypanosoma cruzi, is an endemic disease that affects most part of Latin America. About 18 million people are infected by the parasite and around 21 thousand deaths are related to Chagas\' disease each year. Nowadays, 100 millions of people are estimated to be under the risk of infection in the 18 countries of the endemic areas. The therapeutic armamentarium available against Chagas\' disease is comprehended by only two drugs, nifurtmox and benznidazol, which are not effective in the chronic phase of the disease. Cruza in, the most abundant cysteine protease of the parasite, is essential in all stages of the cellular development of the parasite and responsible for invasion and modification of the immunologic system of the human host. Besides, it has differences relatively to those enzymes in the humans. So, it is an excellent biochemical target for searching new agents against T. cruzi. This said and in the view of cruzain specificity, understanding the mechanism of interaction of compounds with this enzyme is considered very interesting in order to design derivatives with potential anti-Chagas\'disease. The present work had the objective of elucidating the affinity of different classes \'of compounds to the enzyme, in the rational search for new trypanomicides. So, mutual peptide prodrugs, derived from primaquine (PQ) and nitrofurazone (NF), previously synthesized, and designed double peptide prodrugs of hydroxymethylnitrofurazone (NFOH), which synthesis has been studied, were submitted to molecular modeling and docking studies. The peptides were chosen based on specific cleavage by cruzain. The interaction with the enzyme and the drug as well as the active compound release mechanism from those derivatives were evaluated. The studies have indicated the dipeptide LysArg as the best carrier to be used in the design of new prodrugs, corroborating what had been earlier observed in the tests of T. cruzi infected cell culture. Based on the possibility of a second mechanism of action through the interaction between cruzain Cys 25 and the semicarbazone group, found in NF and NFOH, analogs of this c/ass of compounds were designed, and synthesized, using classic bioisosterism between sultur and oxygen. Molecular modeling and docking studies have indicated also the participation of this mechanism in the activity of the nitro-heterocyclic compounds referred. All bioisosters showed to inhibit cruzain IC50 between 2.71 µM and 22.83 µM -- also evidencing this mechanism of action. With the purpose of studying the influence of (thio)semicarbazone group present in the synthesized bioisoster derivatives, 20 and 3D QSAR have been developed for a series of compounds reported in the literature, leading to robust and high- preditive leveI models, confirming their action in cruzaine. Those groups might be used in the design of new trypanomicides. Complementing the rational search for new antichagasic compounds, a virtual screening of new ligands, using the structure-based drug design (SBDD) was developed based on a specific pharmacophore model obtained for cruzain. This study have provided the suggestion of twenty compounds from the CHEMDIV data bank with possible inhibitory activity in cruzain. Based on the results obtained, the conclusion is that the studies herein developed with prodrugs and analogs through rational drug design lead to important data towards the research of new candidates as new antichagasic drugs

Potential antichagasic agents: synthesis of hydroxymethylnitrofurazone Mannich bases

A doença de Chagas é endemia que afeta grande parte da América Latina. Estima-se que de 18 a 20 milhões de pessoas estejam infectadas pelo parasita causador da doença e que ocorram, aproximadamente, 50.000 mortes relacionadas à doença de Chagas por ano, nos 21 países da área endêmica. O arsenal terapêutico atualmente usado contra a parasitose, constituído por apenas dois fármacos, é insuficiente, considerando-se, também, que ambos não apresentam ação adequada na fase crônica da doença. Em razão de se tratar de parasitose que acomete apenas países em desenvolvimento, o interesse na pesquisa de novos antichagásicos é consideravelmente baixo por parte dos países que se destacam na introdução de novos fármacos na terapêutica. Resta aos países envolvidos a procura por novas alternativas quimioterápicas. Face ao exposto e ante à alta atividade, em testes in vitro contra o Trypanosoma cruzi, do derivado hidroximetilado do nitrofural, intermediário de síntese de bases de Mannich, obtido em trabalhos anteriores, o objetivo do presente projeto foi sintetizar bases de Mannich desse derivado com aminoácidos lisina e arginina e o dipeptídio lisina-arginina resultante. Os compostos foram sintetizados utilizando-se métodos clássicos e alternativos e grupos protetores, normalmente utilizados na síntese de peptídios e outros, tentativamente empregados, como os grupos metílico e etílico. Em adição, experimentos foram efetuados com o objetivo de otimizar a síntese do hidroximetilnitrofural. Os derivados sintetizados foram analisados por IV, RMN 1H e 13C, e alguns deles, também, por espectrometria de massas. Eles serão submetidos a testes in vitro em cultura de células infectadas com T. cruzi tão logo os grupos protetores sejam removidos. Além disso, serão efetuados testes de liberação para estudo da respectiva estabilidade. Dessa forma, esperam-se obter subsídios importantes para estudos mais aprofundados do seu mecanismo de ação e da possível mutagenicidade envolvida.Chaga\'s disease is an endemic disease that aftects most part of Latin Arnerica. About 18 to 20 million people are infected by the parasite and around 50 thousand deaths are related to Chagas\' disease each year, in the 21 countries of endemic areas. The therapeutic armamentarium available against the disease is constituted by only two drugs and is insufficient, considering, also, that the drugs are not efficient in the chronic phase of the disease. As a parasitosis that only occurs in developing countries, the interest in the research for new antichagasic agents is considerably low in countries that are responsible for the introduction of new drugs in the therapeutics. So, the search for new chemotherapeutic alternatives is a task for the involved countries. In view of the situation and taking into account the high activity in in vitro tests against Trypanosoma cruzi showed by nitrofurazone hydroxymethyl derivative, an intermediary of Mannich bases reaction previously synthesized, the objective of this work was to synthesize its Mannich bases. The carriers used were aminoacids lysine and arginine and its dipeptide, lysinearginine. The compounds were synthesized using classic and alternative methods and protecting groups, currently used in peptide synthesis and others temptatively employed, as methyl and ethyl groups. Also, many experiments were performed in order to achieve the optimization of hydroxymethylnitrofurazone synthesis. The derivatives synthesized were analyzed by IR, 1H and 13C NMR, and some also by mass spectrometry. They will be submitted to in vitro tests with cell infected with T. cruzi as soon as the protecting groups are removed. Besides, tests of drug release will be performed to study their stability. We expect to obtain important information toward better comprehension of their mechanism of action and possible mutagenicity involved

Potential antichagasic agents: synthesis of hydroxymethylnitrofurazone Mannich bases

A doença de Chagas é endemia que afeta grande parte da América Latina. Estima-se que de 18 a 20 milhões de pessoas estejam infectadas pelo parasita causador da doença e que ocorram, aproximadamente, 50.000 mortes relacionadas à doença de Chagas por ano, nos 21 países da área endêmica. O arsenal terapêutico atualmente usado contra a parasitose, constituído por apenas dois fármacos, é insuficiente, considerando-se, também, que ambos não apresentam ação adequada na fase crônica da doença. Em razão de se tratar de parasitose que acomete apenas países em desenvolvimento, o interesse na pesquisa de novos antichagásicos é consideravelmente baixo por parte dos países que se destacam na introdução de novos fármacos na terapêutica. Resta aos países envolvidos a procura por novas alternativas quimioterápicas. Face ao exposto e ante à alta atividade, em testes in vitro contra o Trypanosoma cruzi, do derivado hidroximetilado do nitrofural, intermediário de síntese de bases de Mannich, obtido em trabalhos anteriores, o objetivo do presente projeto foi sintetizar bases de Mannich desse derivado com aminoácidos lisina e arginina e o dipeptídio lisina-arginina resultante. Os compostos foram sintetizados utilizando-se métodos clássicos e alternativos e grupos protetores, normalmente utilizados na síntese de peptídios e outros, tentativamente empregados, como os grupos metílico e etílico. Em adição, experimentos foram efetuados com o objetivo de otimizar a síntese do hidroximetilnitrofural. Os derivados sintetizados foram analisados por IV, RMN 1H e 13C, e alguns deles, também, por espectrometria de massas. Eles serão submetidos a testes in vitro em cultura de células infectadas com T. cruzi tão logo os grupos protetores sejam removidos. Além disso, serão efetuados testes de liberação para estudo da respectiva estabilidade. Dessa forma, esperam-se obter subsídios importantes para estudos mais aprofundados do seu mecanismo de ação e da possível mutagenicidade envolvida.Chaga\'s disease is an endemic disease that aftects most part of Latin Arnerica. About 18 to 20 million people are infected by the parasite and around 50 thousand deaths are related to Chagas\' disease each year, in the 21 countries of endemic areas. The therapeutic armamentarium available against the disease is constituted by only two drugs and is insufficient, considering, also, that the drugs are not efficient in the chronic phase of the disease. As a parasitosis that only occurs in developing countries, the interest in the research for new antichagasic agents is considerably low in countries that are responsible for the introduction of new drugs in the therapeutics. So, the search for new chemotherapeutic alternatives is a task for the involved countries. In view of the situation and taking into account the high activity in in vitro tests against Trypanosoma cruzi showed by nitrofurazone hydroxymethyl derivative, an intermediary of Mannich bases reaction previously synthesized, the objective of this work was to synthesize its Mannich bases. The carriers used were aminoacids lysine and arginine and its dipeptide, lysinearginine. The compounds were synthesized using classic and alternative methods and protecting groups, currently used in peptide synthesis and others temptatively employed, as methyl and ethyl groups. Also, many experiments were performed in order to achieve the optimization of hydroxymethylnitrofurazone synthesis. The derivatives synthesized were analyzed by IR, 1H and 13C NMR, and some also by mass spectrometry. They will be submitted to in vitro tests with cell infected with T. cruzi as soon as the protecting groups are removed. Besides, tests of drug release will be performed to study their stability. We expect to obtain important information toward better comprehension of their mechanism of action and possible mutagenicity involved

Potential antichagasic: the rational pursuit of compounds with selective action by cruzain

A doença de Chagas, parasitose endêmica causada pelo Trypanosoma cruzi, se apresenta como grande causa de morbimortalidade, afetando cerca de 18 milhões de pessoas no continente americano e causando 21.000 mortes, a cada ano. Atualmente, estima-se que 100 milhões de pessoas estejam sob risco de contaminação nos 18 países da área endêmica da doença. A quimioterapia contra a tripanossomíase americana é constituída por apenas dois fármacos, nifurtimox e benznidazol, que não apresentam ação adequada na fase crônica da doença. Por estas razões, é premente a necessidade de novas e mais eficazes alternativas terapêuticas. A cruzaína, mais abundante cisteíno-protease do parasita, é enzima essencial em todos os estágios de modificação celular do parasita e está, também, presente no processo de invasão e modificação do sistema imune do hospedeiro. Além disso, apresenta diferenças em relação a enzimas dessa categoria no hospedeiro. Trata-se, pois, de excelente alvo bioquímico para a pesquisa de novos agentes contra o T. cruzi. Face ao exposto e tendo-se em vista a especificidade da cruzaína, considera-se de grande interesse a compreensão do mecanismo de interação de compostos com essa enzima com o intuito de planejar derivados com atividade antichagásica potencial. O presente trabalho teve o objetivo de elucidar a afinidade de diferentes classes de compostos pela enzima, na busca racional de novos tripanomicidas. Assim, pró-fármacos peptídicos recíprocos, derivados de primaquina(PQ) e de nitrofural(NF), anteriormente sintetizados, e pró-fármacos peptídicos duplos do hidroximetilnitrofural (NFOH) planejados, e cuja síntese foi estudada, foram submetidos a estudos de modelagem molecular e de docking. Os peptídios foram escolhidos com base na cisão específica pelacruzaína. Avaliou-se a interação com a enzima e elucidar o mecanismo de liberação dos fármacos e composto ativo a partir desses derivados. Os estudos indicaram que o melhor transportador a ser utilizado no planejamento de novos pró-fármacos é o dipeptídio LysArg, corroborando o que havia sido observado nos ensaios em cultura de células infectadas . com o T. cruzi. Ante a possibilidade de um segundo mecanismo de ação pela interação entre a Cys25 da cruzaína e o grupo semicarbazona, presente no NF e no NFOH, planejaram-se e sintetizaram-se análogos destes compostos, utilizando bioisosterismo clássico entre enxofre e oxigênio. Estudos de modelagem molecular e docking indicaram a participação também deste mecanismo de ação na atividade dos referidos derivados nitro-heterocíclicos. Todos os bioisósteros apresentaram ação inibitória na cruzaína IC50 entre 2,71 µM e 22,83 µM - evidenciando, também, este mecanismo de ação. Com o objetivo de se estudar a influência do grupamento (tio)semicarbazona presente nos derivados bioisostéricos sintetizados, realizaram-se estudos de QSAR 20 e 3D em série de compostos descritos na literatura, obtendo-se modelos robustos e com grau elevado de predição, comprovando a ação na cruzaína. Tais grupos podem ser utilizados no planejamento de novos tripanomicidas. Complementando a busca racional de novos antichagásicos potenciais, efetuou-se triagem virtual de novos ligantes utilizando o planejamento racional com base na estrutura do receptor (SBDD) a partir de modelo farmacofórico específico obtido para a cruzaína. Esse estudo proporcionou a sugestão de vinte moléculas a partir do banco de dados CHEMDIV, com possível ação inibitória da enzima. Com base nos resultados obtidos, conclui-se que os estudos realizados com pró-fármacos e análogos por meio de processos racionais de planejamento forneceram dados importantes para a pesquisa de candidatos a novos fármacos antichagásicos.Chagas \' disease, a parasitosis caused by Trypanosoma cruzi, is an endemic disease that affects most part of Latin America. About 18 million people are infected by the parasite and around 21 thousand deaths are related to Chagas\' disease each year. Nowadays, 100 millions of people are estimated to be under the risk of infection in the 18 countries of the endemic areas. The therapeutic armamentarium available against Chagas\' disease is comprehended by only two drugs, nifurtmox and benznidazol, which are not effective in the chronic phase of the disease. Cruza in, the most abundant cysteine protease of the parasite, is essential in all stages of the cellular development of the parasite and responsible for invasion and modification of the immunologic system of the human host. Besides, it has differences relatively to those enzymes in the humans. So, it is an excellent biochemical target for searching new agents against T. cruzi. This said and in the view of cruzain specificity, understanding the mechanism of interaction of compounds with this enzyme is considered very interesting in order to design derivatives with potential anti-Chagas\'disease. The present work had the objective of elucidating the affinity of different classes \'of compounds to the enzyme, in the rational search for new trypanomicides. So, mutual peptide prodrugs, derived from primaquine (PQ) and nitrofurazone (NF), previously synthesized, and designed double peptide prodrugs of hydroxymethylnitrofurazone (NFOH), which synthesis has been studied, were submitted to molecular modeling and docking studies. The peptides were chosen based on specific cleavage by cruzain. The interaction with the enzyme and the drug as well as the active compound release mechanism from those derivatives were evaluated. The studies have indicated the dipeptide LysArg as the best carrier to be used in the design of new prodrugs, corroborating what had been earlier observed in the tests of T. cruzi infected cell culture. Based on the possibility of a second mechanism of action through the interaction between cruzain Cys 25 and the semicarbazone group, found in NF and NFOH, analogs of this c/ass of compounds were designed, and synthesized, using classic bioisosterism between sultur and oxygen. Molecular modeling and docking studies have indicated also the participation of this mechanism in the activity of the nitro-heterocyclic compounds referred. All bioisosters showed to inhibit cruzain IC50 between 2.71 µM and 22.83 µM -- also evidencing this mechanism of action. With the purpose of studying the influence of (thio)semicarbazone group present in the synthesized bioisoster derivatives, 20 and 3D QSAR have been developed for a series of compounds reported in the literature, leading to robust and high- preditive leveI models, confirming their action in cruzaine. Those groups might be used in the design of new trypanomicides. Complementing the rational search for new antichagasic compounds, a virtual screening of new ligands, using the structure-based drug design (SBDD) was developed based on a specific pharmacophore model obtained for cruzain. This study have provided the suggestion of twenty compounds from the CHEMDIV data bank with possible inhibitory activity in cruzain. Based on the results obtained, the conclusion is that the studies herein developed with prodrugs and analogs through rational drug design lead to important data towards the research of new candidates as new antichagasic drugs

Simulação do espectro de absorção UV do filtro solar p-metoxicinamato de etilexila empregando métodos teóricos (TD-DFT)

FAPESP (11/11499-0)Res. MED06

Molecular Modeling Suggests Cruzain Specificity for Peptide Primaquine Prodrugs

Chagas' disease, infection caused by the protozoan Trypanosoma cruzi, is an important, social and medical ailment in the Latin America. This disease is endemic in 21 countries, mostly Latin America countries, with more than 300,000 new cases every year and about 16-18 million infected people. Current therapy is not effective in the chronic phase of the disease. Thus, new and better drugs are urgently needed. In this sense, the in vitro activity of primaquine (PQ) was reported. Based on this, peptide prodrugs of primaquine containing dipeptides - lysine-arginine (LysArg), phenylalanine-alanine (PheAla) and phenylalanine-arginine (PheArg) -- as carriers, were designed to be selectively cleaved by cruzain, a specific cysteine protease of T. cruzi. The prodrugs have shown to be active against tripomastigote forms according to this order: LysArg-PQ> PheAla-PQ> PheArg-PQ. The molecular mechanism of action considered a probable nucleophilic attack of the catalytic residue of cruzain (Cys25) on the respective prodrug amide carbonyl carbon, releasing PQ. In order to test this hypothesis, molecular modeling studies were performed, physicochemical parameters and stereoelectronic features calculated by using the AM1 semi-empirical method suggest that the amide carbonyl carbon is favorable for cleavage, where the LysArg showed the most electronic reactive and sterically disposable, leading to the prodrug release and action. In addition, the docking study indicates the occurrence of specific interactions between prodrugs and the pockets S1 and S2 of cruzain through the dipeptides carriers, being the distance between cruzain Cys25 and the amide carbonyl group related to the biological activity of the prodrugs.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Molecular Modeling Suggests Cruzain Specificity for Peptide Primaquine Prodrugs

Chagas` disease, infection caused by the protozoan Trypanosoma cruzi, is an important, social and medical ailment in the Latin America. This disease is endemic in 21 countries, mostly Latin America countries, with more than 300,000 new cases every year and about 16-18 million infected people. Current therapy is not effective in the chronic phase of the disease. Thus, new and better drugs are urgently needed. In this sense, the in vitro activity of primaquine (PQ) was reported. Based on this, peptide prodrugs of primaquine containing dipeptides - lysine-arginine (LysArg), phenylalanine-alanine (PheAla) and phenylalanine-arginine (PheArg) -- as carriers, were designed to be selectively cleaved by cruzain, a specific cysteine protease of T. cruzi. The prodrugs have shown to be active against tripomastigote forms according to this order: LysArg-PQ> PheAla-PQ> PheArg-PQ. The molecular mechanism of action considered a probable nucleophilic attack of the catalytic residue of cruzain (Cys25) on the respective prodrug amide carbonyl carbon, releasing PQ. In order to test this hypothesis, molecular modeling studies were performed, physicochemical parameters and stereoelectronic features calculated by using the AM1 semi-empirical method suggest that the amide carbonyl carbon is favorable for cleavage, where the LysArg showed the most electronic reactive and sterically disposable, leading to the prodrug release and action. In addition, the docking study indicates the occurrence of specific interactions between prodrugs and the pockets S1 and S2 of cruzain through the dipeptides carriers, being the distance between cruzain Cys25 and the amide carbonyl group related to the biological activity of the prodrugs.FAPESP[01/01192-3]FAPESP[08/58723-0]CAPES-Prodoc[00019 03-8]CNP

Convergent QSAR Models for the Prediction of Cruzain Inhibitors

Chagas disease is a parasitosis caused by Trypanosoma cruzi. Cruzain, the major cysteine protease from T. cruzi, is an excellent therapeutic target in the search for antichagasic drugs. It is important in the role of cell invasion, replication, differentiation, and metabolism of the parasite. In this work, we developed and assessed multiple quantitative structure-activity relationship (QSAR) models for a set of 61 cruzain inhibitors. These models include two-dimensional (2D) QSAR, three-dimensional (3D) QSAR, such as comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA), and Hologram QSAR (HQSAR). In total, we generated 10 major and 114 minor model variations. Molecular docking was used to successfully align the molecules. All CoMFA and CoMSIA models, which incorporate multiple fields, demonstrated robustness in our analysis. Steric fields exhibited satisfactory convergence in the contour maps, while the electrostatic field converged into a single small region. The HQSAR model taking into consideration only Atoms and Connectivity, with fragment sizes ranging from two to five atoms, was considered the best of the HQSAR variations, despite exhibiting a higher level of deviance. In total, 78 model variations meet the minimum requirements to be considered acceptable. We found that using as few as five descriptors it is possible to obtain robust results with 2D-QSAR. Models such as Random Forest, Tree Ensemble, Linear Regression, and HQSAR are recommended for working with large data sets, while the 3D-QSAR models are intended to study the geometry of the ligands, to optimize them into new and better performing antichagasics. Virtual Screening of a set of hydrazones, guided by the top-performing models, identified promising candidates for experimental validation. Among them, dv007 and dv015 exhibited consistently high predicted pIC50 values (7.26 and 7.24, respectively), making them compelling candidates for further drug development

Convergent QSAR Models for the Prediction of Cruzain Inhibitors

Chagas disease is a parasitosis caused by Trypanosoma cruzi. Cruzain, the major cysteine protease from T. cruzi, is an excellent therapeutic target in the search for antichagasic drugs. It is important in the role of cell invasion, replication, differentiation, and metabolism of the parasite. In this work, we developed and assessed multiple quantitative structure-activity relationship (QSAR) models for a set of 61 cruzain inhibitors. These models include two-dimensional (2D) QSAR, three-dimensional (3D) QSAR, such as comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA), and Hologram QSAR (HQSAR). In total, we generated 10 major and 114 minor model variations. Molecular docking was used to successfully align the molecules. All CoMFA and CoMSIA models, which incorporate multiple fields, demonstrated robustness in our analysis. Steric fields exhibited satisfactory convergence in the contour maps, while the electrostatic field converged into a single small region. The HQSAR model taking into consideration only Atoms and Connectivity, with fragment sizes ranging from two to five atoms, was considered the best of the HQSAR variations, despite exhibiting a higher level of deviance. In total, 78 model variations meet the minimum requirements to be considered acceptable. We found that using as few as five descriptors it is possible to obtain robust results with 2D-QSAR. Models such as Random Forest, Tree Ensemble, Linear Regression, and HQSAR are recommended for working with large data sets, while the 3D-QSAR models are intended to study the geometry of the ligands, to optimize them into new and better performing antichagasics. Virtual Screening of a set of hydrazones, guided by the top-performing models, identified promising candidates for experimental validation. Among them, dv007 and dv015 exhibited consistently high predicted pIC50 values (7.26 and 7.24, respectively), making them compelling candidates for further drug development