Data/hora: 05/06/2024 19:11:46

Provedor de dados: 	56	
País: 	Brazil	
Título: 	Inotropic effects of extracts of Psidium guajava L. (guava) leaves on the guinea pig atrium	
Autores: 	Conde Garcia,E.A.; Nascimento,V.T.; Santiago Santos,A.B.	
Data: 	2003-05-01	
Ano: 	2003	
Palavras-chave: 	Heart contractility; Guinea pig; Myocardial inotropism; Psidium guajava L.; Folk medicine.	
Resumo: 	Many pharmacological effects have been ascribed to extracts of Psidium guajava L. (guava) leaves. However, in spite of its widespread use in Brazilian folk medicine and a reasonable number of scientific reports about it, we could not find any study dealing with its action on the mammalian myocardium. In the present study, by measuring isometric force, we observed that the crude extract of P. guajava (water-alcohol extract obtained by macerating dry leaves) depresses the guinea pig atrial contractility in a concentration-dependent fashion (N = 8 hearts, 15 trials). The compound with cardiac activity was concentrated by extraction in a Soxhlet apparatus using 17 M glacial acetic acid after removing the less polar fractions (hexane, chloroform, acetone, ethanol and methanol), suggesting that this compound is a highly polar substance. In the isolated guinea pig left atrium the acetic acid fraction (10-800 mg/l) of P. guajava 1) reversibly decreased myocardial force in a concentration-dependent fashion (EC50 = 0.07g/l, N = 5 hearts, 9 trials, P&lt;0.05), 2) increased the atrial relaxation time measured at 20% of the force amplitude up to 35% (91 ± 15 to 123 ± 30 ms, N = 3 hearts, 6 trials, P&lt;0.05), 3) abolished the positive staircase effect (Bowditch phenomenon) in a concentration-dependent fashion suggesting a decrease of the cellular inward calcium current (N = 4 hearts, 8 trials, P&lt;0.05), and 4) its inotropic effect was abolished by cholinergic receptor blockade with 1.5 mM atropine sulfate, indicating a cholinergic involvement in the mechanism of action of the extract (N = 7 hearts, 15 trials, P&lt;0.05). The acetic acid extract was 20 times more potent than crude extract (EC50 = 1.4 g/l). The results showed that extracts from P. guajava leaves depress myocardial inotropism.	
Tipo: 	Info:eu-repo/semantics/article	
Idioma: 	Inglês	
Identificador: 	http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2003000500014	
Editor: 	Associação Brasileira de Divulgação Científica	
Relação: 	10.1590/S0100-879X2003000500014	
Formato: 	text/html	
Fonte: 	Brazilian Journal of Medical and Biological Research  v.36 n.5 2003	
Fonte: 	info:eu-repo/semantics/openAccess