Antiplasmodial Activity of Hydroalcoholic Extract from Jucá (Libidibia ferrea) Pods.

Malaria is an infectious and parasitic disease caused by protozoa of the genus Plasmodium, which affects millions of people in tropical and subtropical areas. Recently, there have been multiple reports of drug resistance in Plasmodium populations, leading to the search for potential new active compounds against the parasite. Thus, we aimed to evaluate the in vitro antiplasmodial activity and cytotoxicity of the hydroalcoholic extract of Jucá (Libidibia ferrea) in serial concentrations. Jucá was used in the form of a freeze-dried hydroalcoholic extract. For the cytotoxicity assay, the(3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) method with the WI-26VA4 human cell line was used. For the antiplasmodial activity, Plasmodium falciparum synchronized cultures were treated with serial concentrations (0.2 to 50 µg/mL) of the Jucá extract. In terms of the chemical composition of the Jucá extract, gas chromatography coupled to mass spectrometry measurements revealed the main compounds as ellagic acid, valoneic acid dilactone, gallotannin, and gallic acid. The Jucá hydroalcoholic extract did not show cytotoxic activity per MTT, with an IC50 value greater than 100 µg/mL. Regarding the antiplasmodial activity, the Jucá extract presented an IC50 of 11.10 µg/mL with a selective index of nine. Because of its antiplasmodial activity at the tested concentrations and low toxicity, the Jucá extract is presented as a candidate for herbal medicine in the treatment of malaria. To the best of our knowledge, this is the first report of antiplasmodial activity in Jucá.

Antiplasmodial activity of coumarins isolated from Polygala boliviensis: in vitro and in silico studies.

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC50=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH.Communicated by Ramaswamy H. Sarma.

In vitro and in silico assessment of new beta amino ketones with antiplasmodial activity.

BACKGROUND: Based on the current need for new drugs against malaria, our study evaluated eight beta amino ketones in silico and in vitro for potential antimalarial activity. METHODS: Using the Brazilian Malaria Molecular Targets (BraMMT) and OCTOPUS® software programs, the pattern of interactions of beta-amino ketones was described against different proteins of P. falciparum and screened to evaluate their physicochemical properties. The in vitro antiplasmodial activities of the compounds were evaluated using a SYBR Green-based assay. In parallel, in vitro cytotoxic data were obtained using the MTT assay. RESULTS: Among the eight compounds, compound 1 was the most active and selective against P. falciparum (IC50 = 0.98 µM; SI > 60). Six targets were identified in BraMMT that interact with compounds exhibiting a stronger binding energy than the crystallographic ligand: P. falciparum triophosphate phosphoglycolate complex (1LYX), P. falciparum reductase (2OK8), PfPK7 (2PML), P. falciparum glutaredoxin (4N0Z), PfATP6, and PfHT. CONCLUSIONS: The physicochemical properties of compound 1 were compatible with the set of criteria established by the Lipinski rule and demonstrated its potential as a drug prototype for antiplasmodial activity.

Brazilian malaria molecular targets (BraMMT): selected receptors for virtual high-throughput screening experiments.

BACKGROUND: Owing to increased spending on pharmaceuticals since 2010, discussions about rising costs for the development of new medical technologies have been focused on the pharmaceutical industry. Computational techniques have been developed to reduce costs associated with new drug development. Among these techniques, virtual high-throughput screening (vHTS) can contribute to the drug discovery process by providing tools to search for new drugs with the ability to bind a specific molecular target. OBJECTIVES: In this context, Brazilian malaria molecular targets (BraMMT) was generated to execute vHTS experiments on selected molecular targets of Plasmodium falciparum. METHODS: In this study, 35 molecular targets of P. falciparum were built and evaluated against known antimalarial compounds. FINDINGS: As a result, it could predict the correct molecular target of market drugs, such as artemisinin. In addition, our findings suggested a new pharmacological mechanism for quinine, which includes inhibition of falcipain-II and a potential new antimalarial candidate, clioquinol. MAIN CONCLUSIONS: The BraMMT is available to perform vHTS experiments using OCTOPUS or Raccoon software to improve the search for new antimalarial compounds. It can be retrieved from www.drugdiscovery.com.br or download of Supplementary data.

In vitro and in vivo antimalarial potential of oleoresin obtained from Copaifera reticulata Ducke (Fabaceae) in the Brazilian Amazon rainforest.

BACKGROUND: In view of the wide variety of the flora of the Amazon region, many plants have been studied in the search for new antimalarial agents. Copaifera reticulata is a tree distributed throughout the Amazon region which contains an oleoresin rich in sesquiterpenes and diterpenes with ß-caryophyllene as the major compound. The oleoresin has demonstrated antiparasitic activity against Leishmania amazonensis. Because of this previously reported activity, this oleoresin would be expected to also have antimalarial activity. PURPOSE: In this study we evaluated the in vitro and in vivo antimalarial potential of C. reticulata oleoresin. METHODS: In vitro assays were done using P. falciparum W2 and 3D7 strains and the human fibroblast cell line 26VA Wi-4. For in vivo analysis, BALB/c mice were infected with approximately 106 erythrocytes parasitized by P. berghei and their parasitemia levels were observed over 7 days of treatment with C. reticulata; hematological and biochemical parameters were analyzed at the end of experiment. RESULTS: The oleoresin of C. reticulata containing the sesquiterpenes ß-caryophyllene (41.7%) and ß-bisabolene (18.6%) was active against the P. falciparum W2 and 3D7 strains (IC50 = 1.66 and 2.54 µg/ml, respectively) and showed low cytotoxicity against the 26VA Wi-4 cell line (IC50 > 100 µg/ml). The C. reticulata oleoresin reduced the parasitemia levels of infected animals and doses of 200 and 100 mg/kg/day reached a rate of parasitemia elimination resembling that obtained with artemisinin 100 mg/kg/day. In addition, treatment with oleoresin improved the hypoglycemic, hematologic, hepatic and renal parameters of the infected animals. CONCLUSION: The oleoresin of C. reticulata has antimalarial properties and future investigations are necessary to elucidate its mechanism of action.

Structure-based drug design studies of the interactions of ent-kaurane diterpenes derived from Wedelia paludosa with the Plasmodium falciparum sarco/endoplasmic reticulum Ca²âº-ATPase PfATP6.

Malaria is responsible for more deaths around the world than any other parasitic disease. Due to the emergence of strains that are resistant to the current chemotherapeutic antimalarial arsenal, the search for new antimalarial drugs remains urgent though hampered by a lack of knowledge regarding the molecular mechanisms of artemisinin resistance. Semisynthetic compounds derived from diterpenes from the medicinal plant Wedelia paludosa were tested in silico against the Plasmodium falciparum Ca2+-ATPase, PfATP6. This protein was constructed by comparative modelling using the three-dimensional structure of a homologous protein, 1IWO, as a scaffold. Compound 21 showed the best docking scores, indicating a better interaction with PfATP6 than that of thapsigargin, the natural inhibitor. Inhibition of PfATP6 by diterpene compounds could promote a change in calcium homeostasis, leading to parasite death. These data suggest PfATP6 as a potential target for the antimalarial ent-kaurane diterpenes.

Structure-based drug design studies of the interactions of ent-kaurane diterpenes derived from Wedelia paludosa with the Plasmodium falciparum sarco/endoplasmic reticulum Ca2+-ATPase PfATP6

Malaria is responsible for more deaths around the world than any other parasitic disease. Due to the emergence of strains that are resistant to the current chemotherapeutic antimalarial arsenal, the search for new antimalarial drugs remains urgent though hampered by a lack of knowledge regarding the molecular mechanisms of artemisinin resistance. Semisynthetic compounds derived from diterpenes from the medicinal plant Wedelia paludosa were tested in silico against the Plasmodium falciparum Ca2+-ATPase, PfATP6. This protein was constructed by comparative modelling using the three-dimensional structure of a homologous protein, 1IWO, as a scaffold. Compound 21 showed the best docking scores, indicating a better interaction with PfATP6 than that of thapsigargin, the natural inhibitor. Inhibition of PfATP6 by diterpene compounds could promote a change in calcium homeostasis, leading to parasite death. These data suggest PfATP6 as a potential target for the antimalarial ent-kaurane diterpenes.

Quimioterapia antimalárica experimental e mecanismos de ação de antimaláricos envolvendo íons cálcio e prótons

Limitações atuais do arsenal terapêutico na malária humana exigem a busca de novos medicamentos. Além da grande importância econômica e social da malária e da resistência do P. falciparum a cloroquina e outros derivados quinolínicos, as associações medicamentosas compostas por artemisinina e seus derivados apresentam custos de produção elevados, dificultando seu emprego em regiões em desenvolvimento, especialmente no continente africano. Nesse trabalho testamos a atividade antimalárica de: (i) associações dos antimaláricos artesunato (AS) e mefloquina (MQ) com ciprofloxacina, uma fluoroquinolona sintética empregada contra infecções bacterianas; (ii) moléculas obtidas por síntese química, como anti-retrovrais, endoperóxidos, e uma nova molécula híbrida denominada MEFAS e (iii) extratos e compostos purificados de plantas medicinais como falsas quinas e Holostylis reniformis, utilizadas popularmente no tratamento de quadros febris e dispepsias. Os testes esquizonticidas foram feitos em cultivos contínuos de P. falciparum avaliando-se o crescimento das fases intraeritrocitárias através de duas metodologias (teste tradicional ou o ensaio de incorporação de hipoxantina tritiada); e utilizando camundongos inoculados com P. berghei. Estabelecemos ainda um protocolo com sondas fluorescentes que permitiu trabalhar com trofozoítos de P. falciparum viáveis em eritrócitos infectados e acompanhar, em tempo real, ações de potenciais antimaláricos sobre a homeostasia iônica dos parasitos, identificando possíveis alvos intracelulares dos mesmos.

Observamos um sinergismo das associações de MQ e/ou AS com ciprofloxacina, combinações essas que representam uma alternativa promissora para o tratamento da malária humana, assim como os anti-retrovirais testados, todos parcialmente ativos. MEFAS, uma nova molécula híbrida entre os antimaláricos MQ e AS mostrou intensa ação antimalárica in vitro e in vivo. Estudos do mecanismo de ação através de microscopia confocal da MEFAS mostram que a molécula atua simultâneamente em dois compartimentos intracelulares de P. falciparum, o retículo endoplasmático liso e o vacúolo digestivo. Dois endoperóxidos sintéticos derivados do ácido abiético, também ativos na malária, agiram sobre o retículo endoplasmático liso do parasito, mas necessitam de modificações químicas visando potenciar sua ação esquizonticida. Avaliamos ainda a atividade farmacológica de extratos de R. ferruginea e S. pseudoquina que inibiram parcialmente a parasitemia em camundongos e/ou o crescimento de P. falciparum in vitro e de lignanas isoladas de H. renformis que mostrou intensa atividade antimalárica. O conhecimento científico gerado neste trabalho deverá contribuir para a formulação de novos fármacos com ação antimalárica seletiva

Quimioterapia antimalárica experimental e mecanismos de ação de antimaláricos envolvendo íons cálcio e prótons / Experimental chemotherapy and antimalarial mechanisms of action of antimalarial drugs involving calcium ions and protons

Limitações atuais do arsenal terapêutico na malária humana exigem a busca de novos medicamentos. Além da grande importância econômica e social da malária e da resistência do P. falciparum a cloroquina e outros derivados quinolínicos, as associações medicamentosas compostas por artemisinina e seus derivados apresentam custos de produção elevados, dificultando seu emprego em regiões em desenvolvimento, especialmente no continente africano. Nesse trabalho testamos a atividade antimalárica de: (i) associações dos antimaláricos artesunato (AS) e mefloquina (MQ) com ciprofloxacina, uma fluoroquinolona sintética empregada contra infecções bacterianas; (ii) moléculas obtidas por síntese química, como anti-retrovrais, endoperóxidos, e uma nova molécula híbrida denominada MEFAS e (iii) extratos e compostos purificados de plantas medicinais como falsas quinas e Holostylis reniformis, utilizadas popularmente no tratamento de quadros febris e dispepsias. Os testes esquizonticidas foram feitos em cultivos contínuos de P. falciparum avaliando-se o crescimento das fases intraeritrocitárias através de duas metodologias (teste tradicional ou o ensaio de incorporação de hipoxantina tritiada); e utilizando camundongos inoculados com P. berghei. Estabelecemos ainda um protocolo com sondas fluorescentes que permitiu trabalhar com trofozoítos de P. falciparum viáveis em eritrócitos infectados e acompanhar, em tempo real, ações de potenciais antimaláricos sobre a homeostasia iônica dos parasitos, identificando possíveis alvos intracelulares dos mesmos.