RESUMEN
The diterpenes previously isolated from the leaves of Croton zambesicus were tested to evaluate their vasorelaxant activity on the Wistar rat aorta. Their vasorelaxant effect was compared to a series of synthetic trachylobanes and related polycyclic compounds on KCl- or noradrenaline-induced contractions in order to evaluate structure-activity relationships. We demonstrate the vasorelaxant properties of some pure trachylobane diterpenes at low concentration (IC50 < 10 microM) on KCl-induced contractions, but none have a significant effect in noradrenaline-induced contractions. Comparing structures and activity we observed that a C-14 carbonyl group associated with a C-15 hydroxy or ketone function or a C-3 carbonyl associated with a hydroxymethyl group plays an important role in the vasorelaxant activity of trachylobane diterpenes. We also observed that the absolute configuration or the cleavage of the C13-C16 cyclopropane bond does not have a marked effect on the activity. The cytotoxicity of all of these compounds has also been evaluated on HeLa cells in order to verify that the vasorelaxant activity was not correlated with general cytotoxicity.
Asunto(s)
Croton/química , Diterpenos/aislamiento & purificación , Diterpenos/farmacología , Plantas Medicinales/química , Vasodilatadores/aislamiento & purificación , Vasodilatadores/farmacología , Animales , Aorta/efectos de los fármacos , Benin , Diterpenos/síntesis química , Diterpenos/química , Ensayos de Selección de Medicamentos Antitumorales , Células HeLa , Humanos , Concentración 50 Inhibidora , Estructura Molecular , Hojas de la Planta/química , Ratas , Ratas Wistar , Relación Estructura-Actividad , Vasodilatadores/síntesis química , Vasodilatadores/químicaRESUMEN
A mixture of two new diterpenes was isolated from a dichloromethane extract of Croton zambesicus: ent-18-hydroxytrachyloban-3beta-ol (1) and ent-18-hydroxyisopimara-7,15-diene-3beta-ol (2). The two compounds crystallised together and were separated after derivatisation of the pimarane derivative with osmium tetroxide. The structure of 1 was elucidated by 1D- and 2D-NMR analysis and by X-ray diffraction of a crystal containing both compounds while 2 was only identified by crystallographic data. As this plant is widely used in African folk medicine against hypertension, we have analysed the vasorelaxant activity of the isolated molecules. The mixture of the two compounds inhibited the KCl-induced contraction of male Wistar rat aorta (IC (50) = 1 microg/mL), while the purified trachylobane (compound 1) and the hydroxylated pimarane showed a lower activity than the mixture.
Asunto(s)
Bloqueadores de los Canales de Calcio/farmacología , Croton/química , Diterpenos/farmacología , Vasodilatadores/farmacología , Animales , Antihipertensivos/química , Antihipertensivos/aislamiento & purificación , Antihipertensivos/farmacología , Aorta Torácica/efectos de los fármacos , Aorta Torácica/fisiología , Bloqueadores de los Canales de Calcio/química , Bloqueadores de los Canales de Calcio/aislamiento & purificación , Cristalografía por Rayos X , Diterpenos/química , Diterpenos/aislamiento & purificación , Células HeLa , Humanos , Masculino , Estructura Molecular , Cloruro de Potasio/antagonistas & inhibidores , Ratas , Ratas Wistar , Vasoconstricción/efectos de los fármacos , Vasodilatadores/química , Vasodilatadores/aislamiento & purificaciónRESUMEN
A sensitive and accurate method, combining Soxhlet extraction, solid-phase extraction and capillary gas chromatography, is described for the quantitative determination of four new diterpenes (ent-trachyloban-3beta-ol, ent-18-hydroxy-trachyloban-3-one, ent-trachyloban-3-one and isopimara-7,15-dien-3beta-ol) from the leaves of Croton zambesicus. This is the first method describing the quantification of trachylobane diterpenes in a crude extract. It has been fully validated in order to be able to compare the diterpene composition in other samples of C. zambesicus, which is an important source of trachylobanes.
Asunto(s)
Cromatografía de Gases/métodos , Croton/química , Diterpenos/análisis , Diterpenos/química , Hojas de la Planta/química , Estructura Molecular , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Cassytha filiformis (Lauraceae), a widely distributed parasitic plant, contains several aporphine alkaloids and is often used in African folk medicine to treat cancer, African trypanosomiasis and other diseases. In a previous investigation, we showed that the alkaloid plant extract and the isolated aporphines possessed in vitro cytotoxic properties. In this paper, we evaluated the in vitro activity of the alkaloid extract (IC50 = 2.2 microg/mL) and its three major aporphine alkaloids (actinodaphnine, cassythine, and dicentrine) on Trypanosoma brucei brucei as well as four related commercially available aporphines (bulbocapnine, glaucine, isocorydine, boldine). Only the three alkaloids from Cassytha filiformis were active on the trypanosomes in vitro (IC50 = 3-15 microM). Additionally, we compared the cytotoxicity of these seven compounds on HeLa cells. Glaucine was the most cytotoxic compound on HeLa cells (IC50 = 8.2 microM) in the series. In order to elucidate their mechanism of action, the binding mode of these molecules to DNA was studied by UV absorption, circular and linear dichroism spectroscopy. The results of the optical measurements indicated that all seven aporphines effectively bind to DNA and behave as typical intercalating agents. Biochemical experiments showed that actinodaphnine, cassythine and dicentrine also interfere with the catalytic activity of topoisomerases in contrast to the four other aporphines. These interactions with DNA may explain, at least in part, the effects observed on cancer cells and on trypanosomes.
Asunto(s)
Aporfinas/farmacología , Lauraceae , Fitoterapia , Extractos Vegetales/farmacología , Inhibidores de Topoisomerasa I , Tripanocidas/farmacología , Trypanosoma brucei brucei/efectos de los fármacos , Animales , Antineoplásicos Fitogénicos/administración & dosificación , Antineoplásicos Fitogénicos/farmacología , Antineoplásicos Fitogénicos/uso terapéutico , Aporfinas/administración & dosificación , Aporfinas/uso terapéutico , Inhibidores Enzimáticos/administración & dosificación , Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/uso terapéutico , Células HeLa/efectos de los fármacos , Humanos , Concentración 50 Inhibidora , Extractos Vegetales/administración & dosificación , Extractos Vegetales/uso terapéutico , Tripanocidas/administración & dosificación , Tripanocidas/uso terapéutico , Tripanosomiasis Africana/prevención & controlRESUMEN
Two new trachylobane- and one isopimarane-type diterpenoids: ent-18-hydroxy-trachyloban-3-one; ent-trachyloban-3-one; isopimara-7,15-dien-3beta-ol, were isolated from the leaves of Croton zambesicus, together with trans-phytol, beta-sitosterol, alpha-amyrin and stigmasterol. The structures were determined by extensive NMR techniques and X-ray analysis. The cytotoxicity of these compounds has been evaluated on cancer and non-cancer cell-lines.