RESUMO
OBJECTIVE@#This study aims to evaluate the vasodilatory effect of Chenopodium ambrosioides on the isolated rat aorta, and to explore its mechanism of action.@*METHODS@#The vasorelaxant effect and the mode of action of various extracts from the leaves of C. ambrosioides were evaluated on thoracic aortic rings isolated from Wistar rats. In addition, ethyl acetate and methanol fractions were analyzed, using thin-layer chromatography and high-performance liquid chromatography techniques, for their polyphenolic content.@*RESULTS@#The various active extracts of C. ambrosioides at four concentrations (10, 10, 10 and 1 mg/mL) relaxed the contraction elicited by phenylephrine, in a concentration-dependent manner. This effect seems to be endothelium-dependent, since the vasodilatory effect was entirely absent in denuded aortic rings. The vasorelaxant effect of the methanol fraction (MF) of C. ambrosioides at 1 mg/mL was also inhibited by atropine and tetraethylammonium. This effect remained unchanged by Nω-nitro-l-arginine methyl ester hydrochloride and glibenclamide. The preliminary phytochemical analysis showed that the leaves of C. ambrosioides are rich in phenolic and flavonoid derivatives.@*CONCLUSION@#These results suggest that the MF of C. ambrosioides produces an endothelium-dependent relaxation of the isolated rat aorta, which is thought to be mediated mainly through stimulation of the muscarinic receptors, and probably involving the opening of Ca-activated potassium channels.
RESUMO
Accumulated evidence from experiments conducted in vitro and in vivo favors a beneficial effect of the aqueous extract of Herniaria hirsuta in the preventionand cure of urolithiasis. In the current study, we attempted an initial fractionation of the methanol extract of the plant bio-guided by in vitro and in vivocrystallization assays to determine the nature of compound responsible for the beneficial effect of the plant. A ground plant sample was sequentiallysubmitted to ether and methanol extraction by soxhlet apparatus. Methanolic part was further purified by silica gel chromatography using a series of organicsolvents with different increasing polarity. The fractions were then assayed on calcium oxalate crystallization in vitro and in vivo models. In the whole humanurine, only the fraction eluted with ethanol/water was associated to formation of smaller crystals composed of calcium oxalate dihydrate, similarly to theaqueous extract. When tested at 5 mg/day, it reduced significantly crystal deposition in lithiasic rats. Preliminary identification of plant compound found inthat fraction showed the presence of saponins. We conclude that saponins may be responsible for the beneficial effect of Herniaria hirsuta in the treatmentof kidney stones.
A evidência acumulada por resultados de experimentos conduzidos in vitro e in vivo é favorável a uma ação benéfica do extrato aquoso da Herniaria hirsutana prevenção e cura da urolitíase. No presente estudo, nós nos propusemos a fazer um fracionamento inicial do extrato metanólico da planta,biologicamente guiado por ensaios de cristalização in vivo e in vitro, na tentativa de determinar a natureza do composto responsável pelo efeito benéficoda planta. A planta moída foi submetida seqüencialmente à extração por éter e metanol pelo equipamento "soxhlet". A porção metanólica foi adicionalmentepurificada por cromatografia em gel de sílica empregando uma série de solventes orgânicos de polaridade crescente. As frações foram então testadas emmodelos de cristalização de oxalato de cálcio in vivo e in vitro . Nos testes com urina humana total, somente a fração eluída com etanol/água esteveassociada a cristais menores, compostos de oxalato de cálcio di-hidratado, em similaridade com o extrato aquoso. Quando testada na dose de 5mg/dia,uma redução significativa na deposição de cristais foi observada em ratos litiásicos. Uma identificação preliminar dos compostos contidos naquela fraçãorevelou a presença de saponinas. Nós concluímos que saponinas podem ser responsáveis pelos efeitos benéficos da Herniaria hirsuta no tratamento decálculos renais.
