RESUMO
As part of our continuous studies involving the prospection of natural products from Brazilian flora aiming at the discovery of prototypes for the development of new antiparasitic drugs, the present study describes the isolation of two natural acetylene acetogenins, (2S,3R,4R)-3-hydroxy-4-methyl-2-(n-eicos-11'-yn-19'-enyl)butanolide (1) and (2S,3R,4R)-3-hydroxy-4-methyl-2-(n-eicos-11'-ynyl)butanolide (2), from the seeds of Porcelia macrocarpa (Warm.) R.E. Fries (Annonaceae). Using an ex-vivo assay, compound 1 showed an IC50 value of 29.9 µM against the intracellular amastigote forms of Leishmania (L.) infantum, whereas compound 2 was inactive. These results suggested that the terminal double bond plays an important role in the activity. This effect was also observed for the semisynthetic acetylated (1a and 2a) and eliminated (1b and 2b) derivatives, since only compounds containing a double bond at C-19 displayed activity, resulting in IC50 values of 43.3 µM (1a) and 23.1 µM (1b). In order to evaluate the effect of the triple bond in the antileishmanial potential, the mixture of compounds 1 + 2 was subjected to catalytic hydrogenation to afford a compound 3 containing a saturated side chain. The antiparasitic assays performed with compound 3, acetylated (3a), and eliminated (3b) derivatives confirmed the lack of activity. Furthermore, an in-silico study using the SwissADME online platform was performed to bioactive compounds 1, 1a, and 1b in order to investigate their physicochemical parameters, pharmacokinetics, and drug-likeness. Despite the reduced effect against amastigote forms of the parasite to the purified compounds, different mixtures of compounds 1 + 2, 1a + 2a, and 1b + 2b were prepared and exhibited IC50 values ranging from 7.9 to 38.4 µM, with no toxicity for NCTC mammalian cells (CC50 > 200 µM). Selectivity indexes to these mixtures ranged from >5.2 to >25.3. The obtained results indicate that seeds of Porcelia macrocarpa are a promising source of interesting prototypes for further modifications aiming at the discovery of new antileishmanial drugs.
Assuntos
Acetogeninas/farmacologia , Acetileno/farmacologia , Annonaceae/química , Antiprotozoários/farmacologia , Leishmania/efeitos dos fármacos , Acetogeninas/química , Acetileno/análogos & derivados , Antiprotozoários/química , Humanos , Leishmaniose/tratamento farmacológico , Sementes/químicaRESUMO
Chagas' disease is caused by a parasitic protozoan and affects the poorest population in the world, causing high mortality and morbidity. As a result of the toxicity and long duration of current treatments, the discovery of novel and more efficacious drugs is crucial. In this work, the hexane extract from seeds of Porcelia macrocarpa R.E. Fries (Annonaceae) displayed in vitro antitrypanosomal activity against trypomastigote forms of T. cruzi by the colorimetric MTT assay (IC50 of 65.44 µg/mL). Using chromatographic fractionation over SiO2, this extract afforded a fraction composed by one active compound (IC50 of 10.70 µg/mL), which was chemically characterized as 12,14-octadecadiynoic acid (macrocarpic acid). Additionally, two new inactive acetylene compounds (α,α'-dimacro-carpoyl-ß-oleylglycerol and α-macrocarpoyl-α'-oleylglycerol) were also isolated from the hexane extract. The complete characterization of the isolated compounds was performed by analysis of NMR and MS data as well as preparation of derivatives.
Assuntos
Acetileno/farmacologia , Annonaceae/química , Ácidos Graxos/farmacologia , Extratos Vegetais/farmacologia , Sementes/química , Trypanosoma cruzi/efeitos dos fármacos , Acetileno/química , Doença de Chagas/tratamento farmacológico , Ácidos Graxos/química , Extratos Vegetais/química , Folhas de Planta/química , Dióxido de Silício/químicaRESUMO
The mechanism of delta-aminolevulinate dehydratase (delta-ALA-D) inhibition by phenyl selenoacetylene in vitro was investigated in this study. Phenyl selenoacetylene (40-400 microM) inhibition of delta-aminolevulinate dehydratase from rat liver (low speed supernatant fraction, S1 fraction) was partially prevented by incubation under argon atmosphere and completely prevented by dithiothreitol. After incubation with S1 fraction from rat liver or cysteine (40 mM), phenyl selenoacetylene was partially converted into diphenyl diselenide, which is a stronger inhibitor of delta-aminolevulinate dehydratase than phenyl selenoacetylene. Diphenyl diselenide increased the rate of oxidation of -SH groups, while phenyl selenoacetylene did not affect such oxidation. delta-Aminolevulinate dehydratase purified from bovine liver (Sigma) was less sensitive to phenyl selenoacetylene and diphenyl diselenide than the enzyme from S1 fraction. We propose that the lower sensitivity of purified enzyme to selenides could be related to the formation of selenols due to the presence of dithiothreitol (a reducing agent) in the incubation medium. In agreement, incubation of purified enzyme (Sigma) with diphenyl diselenide (2 microM) and sodium borohydride (a reducing agent) under argon atmosphere significantly increased enzyme activity. Results obtained suggest that delta-aminolevulinate dehydratase inhibition by phenyl selenoacetylene is dependent on its conversion into diphenyl diselenide that induces oxidation of essential -SH groups of delta-aminolevulinate dehydratase. We propose that oxygen could be important in the regeneration of diphenyl diselenide leading to a catalytic oxidation of the enzyme.
Assuntos
Acetileno/análogos & derivados , Acetileno/farmacologia , Derivados de Benzeno/farmacologia , Inibidores Enzimáticos/farmacologia , Compostos Organosselênicos/farmacologia , Sintase do Porfobilinogênio/antagonistas & inibidores , Acetileno/farmacocinética , Animais , Derivados de Benzeno/farmacocinética , Biotransformação , Boroidretos/farmacologia , Ditiotreitol/farmacologia , Inibidores Enzimáticos/farmacocinética , Fígado/efeitos dos fármacos , Fígado/enzimologia , Masculino , Compostos Organosselênicos/farmacocinética , Oxirredução , Ratos , Ratos Wistar , Compostos de Sulfidrila/metabolismoRESUMO
The effect of phenyl selenoacetylene and its selenoxide on delta-aminolevulinate dehydratase from liver of adult rats (mammalian source) and from cucumber leaves (plant source) was investigated. In vivo, selenides can be oxidized to selenoxides by flavin-containing monooxygenases and selenoxides can regenerate selenides by thiol oxidation. The compound phenyl selenoacetylene was converted to selenoxides by reaction with hydrogen peroxide. Phenyl selenoacetylene inhibited mammalian and plant delta-aminolevulinate dehydratase with an IC50 about 250 microM and >400 microM, respectively. Its selenoxide inhibited the enzyme more strongly, with IC50 values of 45 microM and 100 microM for the mammalian and plant source, respectively. The selenoxide inhibitory action was antagonized by dithiothreitol suggesting the involvement of -SH groups. Moreover, delta-aminolevulinate dehydratase from a plant source was inhibited by the selenoxide, suggesting a possible involvement of -SH groups located at a site distinct from the region implicated in Zn2+ binding in mammalian delta-aminolevulinate dehydratase. The results of the present study suggest that (i) delta-aminolevulinate dehydratase is a potential molecular target for phenyl selenoacetylene, due to the oxidation of enzyme sulfhydryl groups, and that (ii) the monooxygenation of this selenocompound, which in vivo could be possibly mediated by flavin-containing monooxigenases, increases its inhibitory effect.
Assuntos
Acetileno/farmacologia , Inibidores Enzimáticos/farmacologia , Peróxido de Hidrogênio/metabolismo , Compostos Organosselênicos/farmacologia , Sintase do Porfobilinogênio/antagonistas & inibidores , Acetileno/análogos & derivados , Animais , Cucumis sativus/química , Ditiotreitol/farmacologia , Relação Dose-Resposta a Droga , Fígado/enzimologia , Masculino , Extratos Vegetais , Folhas de Planta/enzimologia , Ratos , Ratos WistarRESUMO
The immunomodulatory effect of the methanolic extract obtained from dried leaves of Bidens pilosa L. (Asteraceae) and the polyacetylene 2-O-beta-D-glucosyltrideca-11 E-en-3,5,7,9-tetrayn-1,2-diol (PA-1) isolated from it was investigated. The extract inhibited the proliferative response in two in vitro models: human lymphocytes stimulated by 5 microg ml(-1) phytohemagglutinin (PHA) or to 100 nM 12-O-tetradecanoyl phorbol-13-acetate (TPA) plus 0.15 microM ionomycin and murine lymphocytes stimulated by 5 microg ml(-1) concanavalin A (Con A) or in the mixed leukocyte reaction (IC50 = 12.5 to 25 microg ml(-1)). PA-1 was 10-told more potent than the original extract in blocking both human and murine lymphocyte proliferation (IC50 = 1.25 to 2.5 microg ml(-1)). In mice, the intraperitoneal (i.p.) administration of methanolic extract of B. pilosa significantly reduced the size of the popliteal lymph node (PLN) after the inflammation induced by zymosan. One week after the injection of zymosan (150 microg) in the foot pad, PLN weighed 4.6 +/- 0.6 mg in comparison with 0.5 +/- 0.07 mg of the contralateral non-inflamed foot pad. The i.p. treatment with 10 mg extract from day 2 to day 6 after zymosan injection reduced the PLN weight to 1.8 +/- 0.3 mg. The data suggest an immunosuppressive activity of components of B. pilosa that may explain its popularly perceived anti-inflammatory effect.
Assuntos
Anti-Inflamatórios não Esteroides/farmacologia , Imunossupressores/farmacologia , Extratos Vegetais/farmacologia , Acetileno/análogos & derivados , Acetileno/isolamento & purificação , Acetileno/farmacologia , Animais , Anti-Inflamatórios não Esteroides/isolamento & purificação , Asteraceae , Humanos , Imunossupressores/isolamento & purificação , Técnicas In Vitro , Inflamação/tratamento farmacológico , Inflamação/patologia , Ativação Linfocitária/efeitos dos fármacos , Metanol , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Extratos Vegetais/isolamento & purificação , Polímeros/isolamento & purificação , Polímeros/farmacologia , Poli-InosRESUMO
Five new linear acetylenic compounds, namely, pentadeca-6,8,10-triynoic acid (1), octadeca-8,10,12-triynoic acid (2), trans-pentadec-10-en-6,8-diynoic acid (3), cis-hexadec-11-en-7,9-diynoic acid (4), and cis-octadec-12-en-7,9-diynoic acid (5), were isolated from the bark of Heisteria acuminata by bioassay-guided fractionation, using cyclooxygenase (COX) and 5-lipoxygenase (5-LO) assays as models for antiinflammatory activity. The structures of compounds 1-5 were established by NMR, MS, IR, and Raman spectroscopy. These isolated compounds were found to be potent inhibitors of COX. Compounds 4 and 5 were the most potent inhibitors of 5-LO, whereas the other compounds only showed a weak inhibition at the same concentration.
Assuntos
Acetileno/análogos & derivados , Acetileno/isolamento & purificação , Anti-Inflamatórios/isolamento & purificação , Epiderme Vegetal/química , Plantas Medicinais/química , Acetileno/farmacologia , Anti-Inflamatórios/farmacologia , Inibidores de Ciclo-Oxigenase/isolamento & purificação , Inibidores de Ciclo-Oxigenase/farmacologia , Equador , Inibidores de Lipoxigenase/isolamento & purificação , Inibidores de Lipoxigenase/farmacologia , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , EsteroidesRESUMO
Uma das principais técnicas usadas para estudar o efeito inibidor do NO3 na fixaçäo biológica do N2, tem sido o uso de mutantes de estirpes de Rhizobium ou de plantas hospedeiras que näo apresentam o padräo usual de nodulaçäo. Este estudo foi conduzido usando genótipos parentais e mutantes de Lupinus mutabilis, submetidos a dois níveis de NO3: 0 e 5mM, com duas épocas de colheita: sete e dez semanas após emergência. A concentraçäo de 5mM revelou-se da maior importância na inibiçäo da nodulaçäo inicial de Lupinus, apesar de os dados demonstrarem que os mutantes L-114 e L-105 foram mais eficientes quanto a nodulaçäo, N-total e atividade da nitrogenase que a cv. SCG-25, e podem permitir um aumento da fixaçäo de N2. Mas näo houve diferenças na atividade da glutamina sintetase (GS) dos nódulos entre os mutantes L-114, L-105 e a cv. SCG-25, quando as plantas näo receberam NO3, mas na presença de NO3 houve tendência para os mutantes, especialmente para os L-114, apresentarem maior atividade de GS. Isto indica que o mutante L-114 tem uma maior capacidade de assimilaçäo do N fixado, associada com um maior suprimento de carboidratos disponíveis, como indicado pela atividade da PEP-carboxilase. Portanto, a tolerância parcial ao NO3 apresentada pelos mutantes L-114 e L-105 está associada com o fenótipo hipernodulante. Esta sugestäo pode ser observada de reduçäo de acetileno, que foram maiores para o mutante L-114 que para a cv. SCG-25, na presença ou na ausência de NO3
Assuntos
Acetileno/farmacologia , Rhizobium/genética , Nitratos/farmacologia , Glutamato-Amônia Ligase/metabolismoRESUMO
Nitrite, NO, CO, and C2H2 inhibited O2-dependent H2 uptake (H3H oxidation) in denitrifying Azospirillum brasilense Sp7 grown anaerobically on N2O or NO3-. The apparent Ki values for inhibition of O2-dependent H2 uptake were 20 microM for NO2-, 0.4 microM for NO, 28 microM for CO, and 88 microM for C2H2. These inhibitors also affected methylene blue-dependent H2 uptake, presumably by acting directly on the hydrogenase. Nitrite and NO inhibited H2 uptake irreversibly, whereas inhibition due to CO was easily reversed by repeatedly evacuating and backfilling with N2. The C2H2 inhibition was not readily reversed, partly due to difficulty in removing the last traces of this gas from solution. The NO2- inhibition of malate-dependent respiration was readily reversed by repeatedly washing the cells, in contrast to the effect of NO2- on H2-dependent respiration. These results suggest that the low hydrogenase activities observed in NO3(-)-grown cultures of A. brasilense may be due to the irreversible inhibition of hydrogenase by NO2- and NO produced by NO3- reduction.