RESUMEN
Two bis(bibenzyls), isoplagiochins A (1) and B (2) have been isolated by the guidance of inhibitory effect of tubulin polymerization from the liverwort Plagiochila fruticosa (Plagiochilaceae). Isoplagiochins A and B inhibited the polymerization of tubulin at IC(50) 50 and 25muM, respectively. Furthermore structure-activity relationship based on their conformations was discussed. The presence of two aromatic rings which can be connected through two atoms bridge spacer of double bond may serve to maintain the backbone conformation.
Asunto(s)
Hepatophyta/química , Compuestos Macrocíclicos/farmacología , Mitosis/efectos de los fármacos , Enlace de Hidrógeno , Compuestos Macrocíclicos/química , Espectroscopía de Resonancia Magnética , Relación Estructura-ActividadRESUMEN
Cassiarin A 1, a tricyclic alkaloid, isolated from the leaves of Cassia siamea (Leguminosae), shows powerful antimalarial activity against Plasmodium falciparum in vitro as well as P. berghei in vivo, which may be valuable leads for novel antimalarials. Interactions of parasitized red blood cells (pRBCs) with endothelium in aorta are especially important in the processes contribute to the pathogenesis of severe malaria. Nitric oxide (NO) reduces endothelial expression of receptors/adhesion molecules used by pRBC to adhere to vascular endothelium, and reduces cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 showed vasorelaxation activity against rat aortic ring, which may be related with NO production. A series of a hydroxyl and a nitrogen-substituted derivatives and a dehydroxy derivative of 1 have been synthesized as having potent antimalarials against P. falciparum with vasodilator activity, which may reduce cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 exhibited a potent antimalarial activity and a high selectivity index in vitro, suggesting that the presence of a hydroxyl and a nitrogen atom without any substituents may be important to show antimalarial activity. Relative to cassiarin A, a methoxy derivative showed more potent vasorelaxant activity, although it did not show improvement for inhibition of P. falciparum in vitro. These cassiarin derivatives may be promising candidates as antimalarials with different mode of actions.
Asunto(s)
Antimaláricos/síntesis química , Separación Celular , Endotelio , Compuestos Heterocíclicos con 3 Anillos/química , Plasmodium falciparum/efectos de los fármacos , Vasodilatación/efectos de los fármacos , Animales , Antimaláricos/química , Antimaláricos/uso terapéutico , Unión Competitiva/efectos de los fármacos , Moléculas de Adhesión Celular/fisiología , Células Endoteliales , Endotelio/parasitología , Endotelio/fisiología , Malaria Falciparum/tratamiento farmacológico , Microcirculación/efectos de los fármacos , Estructura Molecular , Óxido Nítrico/efectos adversos , Pruebas de Sensibilidad Parasitaria , Ratas , Relación Estructura-ActividadRESUMEN
The first total synthesis of cassiarin A, an antiplasmodial alkaloid isolated from Cassia siamea, was achieved via sequential alkynylation of arenes with Sonogashira coupling and 6- endo-dig-cyclization of phenolic oxygens to the resulting alkynes.
Asunto(s)
Alcaloides/síntesis química , Antimaláricos/síntesis química , Compuestos Heterocíclicos con 3 Anillos/síntesis química , Alcaloides/química , Antimaláricos/química , Cassia/química , Compuestos Heterocíclicos con 3 Anillos/química , Estructura MolecularRESUMEN
A new bischromone, chrobisiamone A (1) with an antiplasmodial activity has been isolated from the leaves of Cassia siamea and the structure was elucidated by 2D NMR analysis. Cyclization of 5-acetonyl-7-hydroxy-2-methylchromone (2) in the presence of ammonium acetate resulted in generation of cassiarin A (3) with an unprecedented tricyclic skeleton, supporting a biogenetic pathway proposed for 3.