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Malaria, Chagas disease, and leishmaniasis are tropical diseases caused by protozoan parasites of the genera Plasmodium, Trypanosoma and Leishmania, respectively. These diseases constitute a major burden on public health in several regions worldwide, mainly affecting low-income populations in economically poor countries. Severe side effects of currently available drug treatments and the emergence of resistant parasites need to be addressed by the development of novel drug candidates. Natural 2,5-Diketopiperazines (2,5-DKPs) constitute N-heterocyclic secondary metabolites with a wide range of biological activities of medicinal interest. Its structural and physicochemical properties make the 2,5-DKP ring a versatile, peptide-like, and stable pharmacophore attractive for synthetic drug design. In the present work, twenty-three novel synthetic 2,5-DKPs, previously synthesized through the versatile Ugi multicomponent reaction, were assayed for their anti-protozoal activities against P. falciparum, T. cruzi, and L. infantum. Some of the 2,5-DKPs have shown promising activities against the target protozoans, with inhibitory concentrations (IC50) ranging from 5.4 to 9.5 µg/mL. The most active compounds also show low cytotoxicity (CC50), affording selectivity indices ≥ 15. Results allowed for observing a clear relationship between the substitution pattern at the aromatic rings of the 2,5-DKPs and their corresponding anti-Plasmodium activity. Finally, calculated drug-like properties of the compounds revealed points for further structure optimization of promising drug candidates.
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Malaria is an endemic disease that affected 229 million people and caused 409 thousand deaths, in 2019. Disease control is based on early diagnosis and specific treatment with antimalarial drugs since no effective vaccines are commercially available to prevent the disease. Drug chemotherapy has a strong historical link to the use of traditional plant infusions and other natural products in various cultures. The research based on such knowledge has yielded two drugs in medicine: the alkaloid quinine from Cinchona species, native in the Amazon highland rain forest in South America, and artemisinin from Artemisia annua, a species from the millenary Chinese medicine. The artemisinin-based combination therapies (ACTs), proven to be highly effective against malaria parasites, and considered as "the last bullet to fight drug-resistant malaria parasites," have limited use now due to the emergence of multidrug resistance. In addition, the limited number of therapeutic options makes urgent the development of new antimalarial drugs. This review focuses on the antimalarial activities of 90 plant species obtained from a search using Pubmed database with keywords "antimalarials," "plants" and "natural products." We selected only papers published in the last 10 years (2011-2020), with a further analysis of those which were tested experimentally in malaria infected mice. Most plant species studied were from the African continent, followed by Asia and South America; their antimalarial activities were evaluated against asexual blood parasites, and only one species was evaluated for transmission blocking activity. Only a few compounds isolated from these plants were active and had their mechanisms of action delineated, thereby limiting the contribution of these medicinal plants as sources of novel antimalarial pharmacophores, which are highly necessary for the development of effective drugs. Nevertheless, the search for bioactive compounds remains as a promising strategy for the development of new antimalarials and the validation of traditional treatments against malaria. One species native in South America, Ampelozyzyphus amazonicus, and is largely used against human malaria in Brazil has a prophylactic effect, interfering with the viability of sporozoites in in vitro and in vivo experiments.
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BACKGROUND: Several species of Aspidosperma plants are referred to as remedies for the treatment of malaria, especially Aspidosperma nitidum. Aspidosperma pyrifolium, also a medicinal plant, is used as a natural anti-inflammatory. Its fractionated extracts were assayed in vitro for activity against malaria parasites and for cytotoxicity. METHODS: Aspidosperma pyrifolium activity was evaluated against Plasmodium falciparum using extracts in vitro. Toxicity towards human hepatoma cells, monkey kidney cells or human monocytes freshly isolated from peripheral blood was also assessed. Anti-malarial activity of selected extracts and fractions that presented in vitro activity were tested in mice with a Plasmodium berghei blood-induced infection. RESULTS: The crude stem bark extract and the alkaloid-rich and ethyl acetate fractions from stem extract showed in vitro activity. None of the crude extracts or fractions was cytotoxic to normal monkey kidney and to a human hepatoma cell lines, or human peripheral blood mononuclear cells; the MDL50 values of all the crude bark extracts and fractions were similar or better when tested on normal cells, with the exception of organic and alkaloidic-rich fractions from stem extract. Two extracts and two fractions tested in vivo caused a significant reduction of P. berghei parasitaemia in experimentally infected mice. CONCLUSION: Considering the high therapeutic index of the alkaloidic-rich fraction from stem extract of A. pyrifolium, it makes the species a candidate for further investigation aiming to produce a new anti-malarial, especially considering that the active extract has no toxicity, i.e., no mutagenic effects in the genototoxicity assays, and that it has an in vivo anti-malarial effect. In its UPLC-HRMS analysis this fraction was shown to have two major components compatible with the bisindole alkaloid Leucoridine B, and a novel compound, which is likely to be responsible for the activity against malaria parasites demonstrated in in vitro tests.
Assuntos
Antimaláricos/farmacologia , Aspidosperma/química , Extratos Vegetais/farmacologia , Plantas Medicinais/química , Plasmodium falciparum/efeitos dos fármacos , Animais , Antimaláricos/administração & dosagem , Antimaláricos/isolamento & purificação , Antimaláricos/toxicidade , Brasil , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Modelos Animais de Doenças , Feminino , Haplorrinos , Humanos , Malária/terapia , Camundongos , Carga Parasitária , Parasitemia , Extratos Vegetais/administração & dosagem , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/toxicidade , Plasmodium berghei/isolamento & purificação , Resultado do TratamentoRESUMO
In spite of recent efforts to eradicate malaria in the world, this parasitic disease is still considered a major public health problem, with a total of 216 million cases of malaria and 445,000 deaths in 2016. Artemisinin-based combination therapies remain effective in most parts of the world, but recent cases of resistance in Southeast Asia have urged for novel approaches to treat malaria caused by Plasmodium falciparum. In this work, we present chloroquine analogs that exhibited high activity against sensitive and chloroquine-resistant P. falciparum blood parasites and were also active against P. berghei infected mice. Among the compounds tested, DAQ, a chloroquine analog with a more linear side chain, was shown to be the most active in vitro and in vivo, with low cytotoxicity, and therefore may serve as the basis for the development of more effective chloroquine analogs to aid malaria eradication.
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Antimaláricos/farmacologia , Antimaláricos/uso terapêutico , Cloroquina/análogos & derivados , Cloroquina/química , Desenho de Fármacos , Plasmodium berghei/efeitos dos fármacos , Plasmodium falciparum/efeitos dos fármacos , Animais , Antimaláricos/isolamento & purificação , Cloroquina/farmacologia , Cloroquina/uso terapêutico , Resistência a Medicamentos , Células Hep G2 , Humanos , Malária/tratamento farmacológico , Camundongos , Testes de Sensibilidade ParasitáriaRESUMO
BACKGROUND: Primaquine is an anti-malarial used to prevent Plasmodium vivax relapses and malaria transmission. However, PQ metabolites cause haemolysis in patients deficient in the enzyme glucose-6-phosphate dehydrogenase (G6PD). Fifteen PQ-thiazolidinone derivatives, synthesized through one-post reactions from primaquine, arenealdehydes and mercaptoacetic acid, were evaluated in parallel in several biological assays, including ability to block malaria transmission to mosquitoes. RESULTS: All primaquine derivatives (PQ-TZs) exhibited lower cell toxicity than primaquine; none caused haemolysis to normal or G6PD-deficient human erythrocytes in vitro. Sera from mice pretreated with the test compounds thus assumed to have drug metabolites, caused no in vitro haemolysis of human erythrocytes, whereas sera from mice pretreated with primaquine did cause haemolysis. The ability of the PQ-TZs to block malaria transmission was evaluated based on the oocyst production and percentage of mosquitoes infected after a blood meal in drug pre-treated animals with experimental malaria caused by either Plasmodium gallinaceum or Plasmodium berghei; four and five PQ-TZs significantly inhibited sporogony in avian and in rodent malaria, respectively. Selected PQ-TZs were tested for their inhibitory activity on P. berghei liver stage development, in mice and in vitro, one compound (4m) caused a 3-day delay in the malaria pre-patent period. CONCLUSIONS: The compound 4m was the most promising, blocking malaria transmissions and reducing the number of exoerythrocytic forms of P. berghei (EEFs) in hepatoma cells in vitro and in mice in vivo. The same compound also caused a 3-day delay in the malaria pre-patent period.
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Eritrócitos/parasitologia , Glucosefosfato Desidrogenase/metabolismo , Malária/tratamento farmacológico , Plasmodium berghei/efeitos dos fármacos , Plasmodium gallinaceum/efeitos dos fármacos , Primaquina/análogos & derivados , Primaquina/farmacologia , Animais , Linhagem Celular Tumoral , Galinhas , Chlorocebus aethiops , Eritrócitos/efeitos dos fármacos , Hemólise/efeitos dos fármacos , Células Hep G2 , Humanos , Malária/transmissão , Malária Aviária/tratamento farmacológico , Malária Aviária/transmissão , Camundongos , Plasmodium berghei/crescimento & desenvolvimento , Plasmodium gallinaceum/crescimento & desenvolvimentoRESUMO
The absence of effective vaccines against malaria and the difficulties associated with controlling mosquito vectors have left chemotherapy as the primary control measure against malaria. However, the emergence and spread of parasite resistance to conventional antimalarial drugs result in a worrisome scenario making the search for new drugs a priority. In the present study, the activities of nine neolignan derivatives were evaluated as follows: (i) against blood forms of chloroquine-resistant Plasmodium falciparum (clone W2), using the tritiated hypoxanthine incorporation and anti-HRPII assays; (ii) for cytotoxic activity against cultured human hepatoma cells (HepG2); and (iii) for intermolecular interaction with the P. falciparum cysteine protease of falcipain-2 (F2) by molecular docking. The neolignan derivatives 9 and 10 showed activity against the blood form of the chloroquine-resistant P. falciparum clone W2 and were not cytotoxic against cultured human hepatoma cells. A molecular docking study of these two neolignans with FP2 revealed several intermolecular interactions that should guide the design of future analogs.
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Antimaláricos/síntese química , Antimaláricos/farmacologia , Lignanas/química , Lignanas/farmacologia , Antimaláricos/metabolismo , Sítios de Ligação , Sobrevivência Celular/efeitos dos fármacos , Cloroquina/farmacologia , Cisteína Endopeptidases/química , Cisteína Endopeptidases/metabolismo , Resistência a Medicamentos/efeitos dos fármacos , Células Hep G2 , Humanos , Ligação de Hidrogênio , Lignanas/metabolismo , Simulação de Acoplamento Molecular , Plasmodium falciparum/efeitos dos fármacos , Proteínas de Protozoários/química , Proteínas de Protozoários/metabolismo , Eletricidade Estática , Relação Estrutura-AtividadeRESUMO
Malaria remains one of the most serious global infectious diseases. An important target for antimalarial chemotherapy is the enzyme dihydroorotate dehydrogenase from Plasmodium falciparum (PfDHODH), which is responsible for the conversion of dihydroorotate to orotate in the de novo pyrimidine biosynthetic pathway. In this study, we have designed and synthesized fifteen 7-arylpyrazolo[1,5-a]pyrimidine derivatives using ring bioisosteric replacement and molecular hybridization of functional groups based on the highly active 5-methyl-N-(naphthalen-2-yl)-2-(trifluoromethyl)- [1,2,4]triazolo[1,5-a]pyrimidin-7-amine. The compounds were tested against Plasmodium falciparum, as antimalarials in mice with P. berghei, and as inhibitors of PfDHODH. Thirteen compounds were found to be active against P. falciparum, with IC50 values ranging from 1.2 ± 0.3 to 92 ± 26 µM in the anti-HRP2 and hypoxanthine assays. Four compounds showed the highest selective index (SI), which is a ratio between cytotoxicity and activity in vitro. The inhibition of PfDHODH showed that compound 30 (R2 = CH3; R5 = CF3; Ar = 7-ß-naphthyl) displayed higher and selective inhibitory activity, with IC50 = 0.16 ± 0.01 µM, followed by 25 (R2 = CH3; R5 = CH3; Ar = 7-ß-Naphthyl) and 19 (R2 = CF3; R5 = CF3; Ar = 7-ß-naphthyl), with IC50 = 4 ± 1 µM and 6 ± 1 µM, respectively. The trifluoromethyl group at the 2- or 5-positions of the pyrazolo[1,5-a]pyrimidine ring led to increased drug activity. The docking results agreed with the values obtained from enzymatic assays.
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Antimaláricos/farmacologia , Inibidores Enzimáticos/farmacologia , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/antagonistas & inibidores , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/enzimologia , Pirimidinas/química , Pirimidinas/farmacologia , Animais , Antimaláricos/química , Antimaláricos/metabolismo , Antimaláricos/toxicidade , Linhagem Celular , Di-Hidro-Orotato Desidrogenase , Avaliação Pré-Clínica de Medicamentos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/metabolismo , Inibidores Enzimáticos/toxicidade , Humanos , Camundongos , Simulação de Acoplamento Molecular , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Conformação Proteica , Pirimidinas/metabolismo , Pirimidinas/toxicidadeRESUMO
Cerebral malaria is caused by Plasmodium falciparum. Atorvastatin (AVA) is a pentasubstituted pyrrole, which has been tested as an adjuvant in the treatment of cerebral malaria. Herein, a new class of hybrids of AVA and aminoquinolines (primaquine and chloroquine derivatives) has been synthesized. The quinolinic moiety was connected to the pentasubstituted pyrrole from AVA by a linker group (CH2)n=2-4 units. The activity of the compounds increased with the size of the carbons chain. Compound with n=4 and 7-chloroquinolinyl has displayed better activity (IC50=0.40 µM) than chloroquine. The primaquine derivative showed IC50=1.41 µM, being less toxic and more active than primaquine.
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Antimaláricos/química , Antimaláricos/farmacologia , Atorvastatina/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Pirróis/farmacologia , Quinolinas/farmacologia , Antimaláricos/síntese química , Atorvastatina/química , Relação Dose-Resposta a Droga , Estrutura Molecular , Testes de Sensibilidade Parasitária , Pirróis/química , Quinolinas/química , Relação Estrutura-AtividadeRESUMO
BACKGROUND: The anti-malarials quinine and artemisinin were isolated from traditionally used plants (Cinchona spp. and Artemisia annua, respectively). The synthetic quinoline anti-malarials (e.g. chloroquine) and semi-synthetic artemisinin derivatives (e.g. artesunate) were developed based on these natural products. Malaria is endemic to the Amazon region where Plasmodium falciparum and Plasmodium vivax drug-resistance is of concern. There is an urgent need for new anti-malarials. Traditionally used Amazonian plants may provide new treatments for drug-resistant P. vivax and P. falciparum. Herein, the in vitro and in vivo antiplasmodial activity and cytotoxicity of medicinal plant extracts were investigated. METHODS: Sixty-nine extracts from 11 plant species were prepared and screened for in vitro activity against P. falciparum K1 strain and for cytotoxicity against human fibroblasts and two melanoma cell lines. Median inhibitory concentrations (IC50) were established against chloroquine-resistant P. falciparum W2 clone using monoclonal anti-HRPII (histidine-rich protein II) antibodies in an enzyme-linked immunosorbent assay. Extracts were evaluated for toxicity against murine macrophages (IC50) and selectivity indices (SI) were determined. Three extracts were also evaluated orally in Plasmodium berghei-infected mice. RESULTS: High in vitro antiplasmodial activity (IC50 = 6.4-9.9 µg/mL) was observed for Andropogon leucostachyus aerial part methanol extracts, Croton cajucara red variety leaf chloroform extracts, Miconia nervosa leaf methanol extracts, and Xylopia amazonica leaf chloroform and branch ethanol extracts. Paullinia cupana branch chloroform extracts and Croton cajucara red variety leaf ethanol extracts were toxic to fibroblasts and or melanoma cells. Xylopia amazonica branch ethanol extracts and Zanthoxylum djalma-batistae branch chloroform extracts were toxic to macrophages (IC50 = 6.9 and 24.7 µg/mL, respectively). Andropogon leucostachyus extracts were the most selective (SI >28.2) and the most active in vivo (at doses of 250 mg/kg, 71% suppression of P. berghei parasitaemia versus untreated controls). CONCLUSIONS: Ethnobotanical or ethnopharmacological reports describe the anti-malarial use of these plants or the antiplasmodial activity of congeneric species. No antiplasmodial activity has been demonstrated previously for the extracts of these plants. Seven plants exhibit in vivo and or in vitro anti-malarial potential. Future work should aim to discover the anti-malarial substances present.
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Antimaláricos/farmacologia , Extratos Vegetais/farmacologia , Plantas/química , Plasmodium falciparum/efeitos dos fármacos , Animais , Antimaláricos/isolamento & purificação , Antimaláricos/toxicidade , Brasil , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Modelos Animais de Doenças , Humanos , Concentração Inibidora 50 , Malária/tratamento farmacológico , Camundongos Endogâmicos BALB C , Parasitemia/tratamento farmacológico , Testes de Sensibilidade Parasitária , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/toxicidade , Plasmodium berghei/efeitos dos fármacos , Resultado do TratamentoRESUMO
This study describes the biochemical and functional characterization of a new metalloproteinase named BbMP-1, isolated from Bothrops brazili venom. BbMP-1 was homogeneous on SDS-PAGE, presented molecular mass of 22,933Da and pI 6.4. The primary structure was partially elucidated with high identity with others metalloproteinases from Viperidae venoms. The enzymatic activity on azocasein was evaluated in different experimental conditions (pH, temperature). A significant reduction in enzyme activity after exposure to chelators of divalent cations (EDTA), reducing agents (DTT), pH less than 5.0 or temperatures higher than 45 °C was observed. BbMP-1 showed activity on fibrinogen degrading Aα chain quickly and to a lesser extent the Bß chain. Also demostrated to be weakly hemorrhagic, presenting however, significant myotoxic and edematogenic activity. The in vitro activity of BbMP-1 against Plasmodium falciparum showed an IC50 of 3.2 ± 2.0 µg/mL. This study may help to understand the pathophysiological effects induced by this group of toxin and their participation in the symptoms observed in cases of snake envenomation. Moreover, this result is representative for this group of proteins and shows the biotechnological potential of BbMP-1 by the demonstration of its antiplasmodial activity.
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Antiparasitários/farmacologia , Bothrops/metabolismo , Venenos de Crotalídeos/enzimologia , Metaloproteases/química , Plasmodium falciparum/efeitos dos fármacos , Animais , Antiparasitários/química , Antiparasitários/isolamento & purificação , Caseínas/química , Caseínas/metabolismo , Eletroforese em Gel de Poliacrilamida , Fibrinogênio/química , Fibrinogênio/metabolismo , Concentração de Íons de Hidrogênio , Concentração Inibidora 50 , Masculino , Metaloproteases/isolamento & purificação , Metaloproteases/farmacologia , Camundongos , Modelos Moleculares , Simulação de Dinâmica Molecular , TemperaturaRESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Malaria is the most important parasitic disease in the world, including in the Amazon region, due to its high incidence. In addition, malaria is difficult to control because of the geographical characteristics of the endemic Amazon region. The quilombola communities of Oriximina, located in remote rainforest areas, have extensive experience with medicinal plants due to their close contact with and dependence on local biodiversity as a therapeutic resource. To search for active bioproducts against malaria, based on in vitro tests using blood culture-derived parasites and plants selected by an ethno-directed approach in traditional quilombola communities of Oriximiná, in the Amazon region of Brazil. MATERIALS AND METHODS: Ethnobotanical data were collected from 35 informants in the quilombola communities of Oriximiná, Brazil, by a free-listing method for the survey of species locally indicated to be effective against malaria and related symptoms. Data were analyzed by salience index (S) and major use agreement. The activity of extracts from 11 plants, selected based on their Salience values (four plants with S>1; seven plants with S<0.1), was measured in vitro in cultures of W2 clone Plasmodium falciparum parasites resistant to chloroquine. RESULTS: Thirty-five ethnospecies comprising 40 different plants belonging to 23 botanical families and 37 genera were listed as antimalarials by the ethno-directed approach. Among these, 11 species selected based on their S values were assayed against P. falciparum. The most active plant extracts, with an IC50 as low as 1.6µg/mL, were obtained from Aspidosperma rigidum (Apocynaceae), Bertholletia excelsa (Lecythidaceae) and Simaba cedron (Simaroubaceae), all of which displayed an S value>1. CONCLUSION: A strong correlation between the consensus of the informants from quilombola communities living in a malaria endemic area and the salience index indicating antiplasmodial activity was observed, where the ethnospecies mostly cited to be effective against malaria produced the most active plant extracts in vitro. It was also evident from the data that these groups approached the treatment of malaria with an holistic view, making use of purgative, depurative, emetic and adaptogen plants.
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Malária/tratamento farmacológico , Fitoterapia , Plantas Medicinais , Adulto , Idoso , Idoso de 80 Anos ou mais , Antimaláricos/farmacologia , Brasil , Etnofarmacologia , Feminino , Humanos , Concentração Inibidora 50 , Masculino , Medicina Tradicional , Pessoa de Meia-Idade , Extratos Vegetais/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Adulto JovemRESUMO
Fifteen quinoline-sulfonamide hybrids, with a 7-chloroquinoline moiety connected by a linker group to arylsulfonamide moieties with different substituents in the 4-position were synthesized and assayed against Plasmodium falciparum. The compounds displayed high schizonticidal blood activity in vitro, with IC50 values ranging from 0.05 to 1.63 µM, in the anti-HPR2 assay against clone W2-chloroquine-resistant; ten of them showed an IC50 (ranging from 0.05 to 0.40 µM) lower than that of chloroquine and sulfadoxine. Among them, two compounds inhibited Plasmodium berghei parasitemia by 47% and 49% on day 5 after mice inoculation. The most active, in vivo, hybrid 13 is considered to be a new prototype for the development of an antimalarial drug against chloroquine-resistant parasites.
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Malária/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Quinolinas/uso terapêutico , Animais , Humanos , Camundongos , Estrutura Molecular , Sulfonamidas/uso terapêuticoRESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Quina is a popular name originally attributed to Cinchona pubescens Vahl (=Cinchona succirubra) and Cinchona. calisaya Wedd., species native from Peru that have the antimalarial alkaloid quinine. In Brazil, bitter barks substitutes for the Peruvian species began to be used centuries ago, and they still are sold in popular markets. To assess the authenticity and the conditions on which samples of quinas have been commercialized, using the DNA barcode, chemical and biological assays. MATERIALS AND METHODS: Starting with 28 samples of barks acquired on a popular market, 23 had their DNA extracted successfully. The regions matK and rbcL were amplified and sequenced for 15 and 23 samples, respectively. Phytochemical analyses were performed by chromatographic methods, and biological essays were done by antimalarial tests in vitro. RESULTS: The identified species belonged to six different families, many of them endangered or with no correlation with use in traditional medicine as a Brazilian quina. The absence of typical bitter chemical substances indicated that barks have been collected from other species or from very young trees. The results of biological essays confirm the lack of standardization of the sold materials. CONCLUSION: The integrated approaches proved to be efficient to evaluate medicinal plants sold in popular markets and can be useful for promoting their better use and conservation.
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Cinchona/química , Conservação dos Recursos Naturais , Medicina Tradicional/métodos , Plantas Medicinais/química , Antimaláricos/química , Antimaláricos/economia , Antimaláricos/isolamento & purificação , Sequência de Bases , Brasil , Cinchona/genética , Comércio , Código de Barras de DNA Taxonômico , Etnofarmacologia , Humanos , Medicina Tradicional/economia , Casca de Planta , Extratos Vegetais/química , Extratos Vegetais/economia , Extratos Vegetais/farmacologia , Plantas Medicinais/genéticaRESUMO
Malaria is one of the most prevalent parasitic diseases in the world. The global importance of this disease, current vector control limitations, and the absence of an effective vaccine make the use of therapeutic antimalarial drugs the main strategy to control malaria. Chloroquine is a cost-effective antimalarial drug with a relatively robust safety profile, or therapeutic index. However, chloroquine is no longer used alone to treat patients with Plasmodium falciparum due to the emergence and spread of chloroquine-resistant strains, which have also been reported for Plasmodium vivax. However, the activity of 1,2,3-triazole derivatives against chloroquine-sensitive and chloroquine-resistant strains of P. falciparum has been reported in the literature. To enhance the anti-P. falciparum activity of quinoline derivatives, we synthesized 11 new quinoline-1H-1,2,3-triazole hybrids with different substituents in the 4-positions of the 1H-1,2,3-triazole ring, which were assayed against the W2-chloroquine-resistant P. falciparum clone. Six compounds exhibited activity against the P. falciparum W2 clone, chloroquine-resistant, with IC50 values ranging from 1.4 to 46 µm. None of these compounds was toxic to a normal monkey kidney cell line, thus exhibiting good selectivity indexes, as high 351 for one compound (11).
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Antimaláricos/química , Antimaláricos/farmacologia , Plasmodium falciparum/fisiologia , Quinolinas/química , Quinolinas/farmacologia , Triazóis/química , Animais , Antimaláricos/síntese química , Apoptose/efeitos dos fármacos , Cloroquina/farmacologia , Resistência a Medicamentos/efeitos dos fármacos , Eritrócitos/parasitologia , Haplorrinos , Humanos , Plasmodium falciparum/efeitos dos fármacos , Quinolinas/síntese químicaRESUMO
BACKGROUND: Several species of Aspidosperma (Apocynaceae) are used as treatments for human diseases in the tropics. Aspidosperma olivaceum, which is used to treat fevers in some regions of Brazil, contains the monoterpenoid indole alkaloids (MIAs) aspidoscarpine, uleine, apparicine, and N-methyl-tetrahydrolivacine. Using bio-guided fractionation and cytotoxicity testing in a human hepatoma cell line, several plant fractions and compounds purified from the bark and leaves of the plant were characterized for specific therapeutic activity (and selectivity index, SI) in vitro against the blood forms of Plasmodium falciparum. METHODS: The activity of A. olivaceum extracts, fractions, and isolated compounds was evaluated against chloroquine (CQ)-resistant P. falciparum blood parasites by in vitro testing with radiolabelled [3H]-hypoxanthine and a monoclonal anti-histidine-rich protein (HRPII) antibody. The cytotoxicity of these fractions and compounds was evaluated in a human hepatoma cell line using a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, and the SI was calculated as the ratio between the toxicity and activity. Two leaf fractions were tested in mice with Plasmodium berghei. RESULTS: All six fractions from the bark and leaf extracts were active in vitro at low doses (IC50 < 5.0 µg/mL) using the anti-HRPII test, and only two (the neutral and basic bark fractions) were toxic to a human cell line (HepG2). The most promising fractions were the crude leaf extract and its basic residue, which had SIs above 50. Among the four pure compounds evaluated, aspidoscarpine in the bark and leaf extracts showed the highest SI at 56; this compound, therefore, represents a possible anti-malarial drug that requires further study. The acidic leaf fraction administered by gavage to mice with blood-induced malaria was also active. CONCLUSION: Using a bio-monitoring approach, it was possible to attribute the anti-P. falciparum activity of A. olivaceum to aspidoscarpine and, to a lesser extent, N-methyl-tetrahydrolivacine; other isolated MIA molecules were active but had lower SIs due to their higher toxicities. These results stood in contrast to previous work in which the anti-malarial activity of other Aspidosperma species was attributed to uleine.
Assuntos
Antimaláricos/farmacologia , Aspidosperma/química , Alcaloides Indólicos/farmacologia , Extratos Vegetais/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Antimaláricos/isolamento & purificação , Antimaláricos/toxicidade , Brasil , Sobrevivência Celular/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Alcaloides Indólicos/isolamento & purificação , Alcaloides Indólicos/toxicidade , Testes de Sensibilidade Parasitária , Casca de Planta/química , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/toxicidade , Folhas de Planta/químicaRESUMO
BACKGROUND: Chloroquine (CQ), a cost effective antimalarial drug with a relatively good safety profile and therapeutic index, is no longer used by itself to treat patients with Plasmodium falciparum due to CQ-resistant strains. P. vivax, representing over 90% of malaria cases in Brazil, despite reported resistance, is treated with CQ as well as with primaquine to block malaria transmission and avoid late P. vivax malaria relapses. Resistance to CQ and other antimalarial drugs influences malaria control, thus monitoring resistance phenotype by parasite genotyping is helpful in endemic areas. METHODS: A total of 47 P. vivax and nine P. falciparum fresh isolates were genetically characterized and tested for CQ, mefloquine (MQ) and artesunate (ART) susceptibility in vitro. The genes mdr1 and pfcrt, likely related to CQ resistance, were analyzed in all isolates. Drug susceptibility was determined using short-term parasite cultures of ring stages for 48 to 72 hour and thick blood smears counts. Each parasite isolate was tested with the antimalarials to measure the geometric mean of 50% inhibitory concentration. RESULTS: The low numbers of P. falciparum isolates reflect the species prevalence in Brazil; most displayed low sensitivity to CQ (IC50 70 nM). However, CQ resistance was rare among P. vivax isolates (IC50 of 32 nM). The majority of P. vivax and P. falciparum isolates were sensitive to ART and MQ. One hundred percent of P. falciparum isolates carried non-synonymous mutations in the pfmdr1 gene in codons 184, 1042 and 1246, 84% in codons 1034 and none in codon 86, a well-known resistance mutation. For the pfcrt gene, mutations were observed in codons 72 and 76 in all P. falciparum isolates. One P. falciparum isolate from Angola, Africa, showing sensitivity to the antimalarials, presented no mutations. In P. vivax, mutations of pvmdr1 and the multidrug resistance gene 1 marker at codon F976 were absent. CONCLUSION: All P. falciparum Brazilian isolates showed CQ resistance and presented non-synonymous mutations in pfmdr1 and pfcrt. CQ resistant genotypes were not present among P. vivax isolates and the IC50 values were low in all samples of the Brazilian West Amazon.
Assuntos
Antimaláricos/farmacologia , DNA de Protozoário/genética , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/genética , Plasmodium vivax/efeitos dos fármacos , Plasmodium vivax/genética , Adulto , Artemisininas/farmacologia , Artesunato , Brasil , Cloroquina/farmacologia , DNA de Protozoário/química , Resistência a Medicamentos , Feminino , Genótipo , Humanos , Concentração Inibidora 50 , Malária/parasitologia , Masculino , Mefloquina/farmacologia , Proteínas de Membrana Transportadoras/genética , Pessoa de Meia-Idade , Proteínas Associadas à Resistência a Múltiplos Medicamentos/genética , Mutação de Sentido Incorreto , Testes de Sensibilidade Parasitária , Plasmodium falciparum/isolamento & purificação , Plasmodium vivax/isolamento & purificação , Proteínas de Protozoários/genéticaRESUMO
DNA topoisomerase I from Plasmodium falciparum (PfTopoI), a potential selective target for chemotherapy and drug development against malaria, is used here, together with human Topo I (HssTopoI), for docking, molecular dynamics (MD) studies and experimental assays. Six synthetic isoflavonoid derivatives and the known PfTopoI inhibitors camptothecin and topotecan were evaluated in parallel. Theoretical results suggest that these compounds dock in the binding site of camptothecin and topotecan inside both enzymes and that LQB223 binds selectively in PfTopoI. In vitro tests against P. falciparum blood parasites corroborated the theoretical findings. The selectivity index (SI) of LQB223 ≥ 98 suggests that this molecule is the most promising in the group of compounds tested. In vivo experiments in mice infected with P. berghei showed that LQB223 has an antimalarial activity similar to that of chloroquine.
Assuntos
Antimaláricos/farmacologia , DNA Topoisomerases Tipo I/metabolismo , Isoflavonas/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/enzimologia , Inibidores da Topoisomerase/farmacologia , Animais , Antimaláricos/química , Antimaláricos/uso terapêutico , Camptotecina/química , Camptotecina/farmacologia , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Resistência a Medicamentos/efeitos dos fármacos , Feminino , Humanos , Concentração Inibidora 50 , Isoflavonas/química , Isoflavonas/uso terapêutico , Malária Falciparum/tratamento farmacológico , Malária Falciparum/parasitologia , Camundongos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Parasitos/efeitos dos fármacos , Plasmodium berghei/efeitos dos fármacos , Termodinâmica , Inibidores da Topoisomerase/química , Topotecan/química , Topotecan/farmacologiaRESUMO
Malaria remains a major world health problem following the emergence and spread of Plasmodium falciparum that is resistant to the majority of antimalarial drugs. This problem has since been aggravated by a decreased sensitivity of Plasmodium vivax to chloroquine. This review discusses strategies for evaluating the antimalarial activity of new compounds in vitro and in animal models ranging from conventional tests to the latest high-throughput screening technologies. Antimalarial discovery approaches include the following: the discovery of antimalarials from natural sources, chemical modifications of existing antimalarials, the development of hybrid compounds, testing of commercially available drugs that have been approved for human use for other diseases and molecular modelling using virtual screening technology and docking. Using these approaches, thousands of new drugs with known molecular specificity and active against P. falciparum have been selected. The inhibition of haemozoin formation in vitro, an indirect test that does not require P. falciparum cultures, has been described and this test is believed to improve antimalarial drug discovery. Clinical trials conducted with new funds from international agencies and the participation of several industries committed to the eradication of malaria should accelerate the discovery of drugs that are as effective as artemisinin derivatives, thus providing new hope for the control of malaria.
Assuntos
Antimaláricos/farmacologia , Descoberta de Drogas , Malária/tratamento farmacológico , Plasmodium/efeitos dos fármacos , Animais , Antimaláricos/química , Ensaios Clínicos como Assunto , Modelos Animais de Doenças , Humanos , Malária/parasitologia , Testes de Sensibilidade Parasitária , Plasmodium/classificaçãoRESUMO
Root extracts of Holostylis reniformis (Aristolochiaceae) yielded three new natural sesquiterpenes, a sesquiterpene with an unusual carbon skeleton, 4,5-seco-guaiane (7-epi-11-hydroxychabrolidione A, 1), a nine-membered lactone with new carbon skeleton (holostylactone, 2), and a new megastigmane [(6S,7E)-6,9-dihydroxy-10-(2'-hydroxy-ethoxy)-4,7-megastigmadien-3-one, 3], together with bulnesol and sitosterol-3-O-β-D-glucopyranoside. The structures of these compounds were determined by spectroscopic analyses and B3LYP/STO-3G** theoretical studies.
Assuntos
Aristolochiaceae/química , Lactonas , Sesquiterpenos de Guaiano/química , Sesquiterpenos , Lactonas/química , Lactonas/isolamento & purificação , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Extratos Vegetais/química , Raízes de Plantas/química , Sesquiterpenos/química , Sesquiterpenos/isolamento & purificação , Sesquiterpenos de Guaiano/isolamento & purificaçãoRESUMO
According to the World Health Organization, half of the World's population, approximately 3.3 billion people, is at risk for developing malaria. Nearly 700,000 deaths each year are associated with the disease. Control of the disease in humans still relies on chemotherapy. Drug resistance is a limiting factor, and the search for new drugs is important. We have designed and synthesized new 2-(trifluoromethyl)[1,2,4]triazolo[1,5-a]pyrimidine derivatives based on bioisosteric replacement of functional groups on the anti-malarial compounds mefloquine and amodiaquine. This approach enabled us to investigate the impact of: (i) ring bioisosteric replacement; (ii) a CF3 group substituted at the 2-position of the [1,2,4]triazolo[1,5-a]pyrimidine scaffold and (iii) a range of amines as substituents at the 7-position of the of heterocyclic ring; on in vitro activity against Plasmodium falciparum. P. falciparum dihydroorotate dehydrogenase (PfDHODH) through strong hydrogen bonds. The presence of a trifluoromethyl group at the 2-position of the [1,2,4]triazolo[1,5-a]pyrimidine ring led to increased drug activity. Thirteen compounds were found to be active, with IC50 values ranging from 0.023 to 20 µM in the anti-HRP2 and hypoxanthine assays. The selectivity index (SI) of the most active derivatives 5, 8, 11 and 16 was found to vary from 1,003 to 18,478.