Extract from leaf of Psidium guajava L depresses the guinea pig atrial contractility by interfering with potassium and calcium channels

Abstract

The negative inotropic effect of aqueous fraction (AqF) obtained from the acetic extract of Psidium guajava L leaf was investigated on the guinea pig left atrium. Myocardial force was measured isometrically (27 ± 0.1 o C, 2 Hz). AqF (100 mg/ml) reduced contractility of about 85 ± 9.4 % (n = 4, p < 0.001, F calc = 51.70, F (0.01; 4; 21) = 5.09, EC 50 = 14.28 ± 3 mg/mL) in a concentration-dependent fashion. This effect was reduced by 20 mM of tetraethylammonium (TEA), increasing EC 50 to 50 ± 7 mg/ml (n = 4, p < 0.001, F calc = 282.13; F (0.01; 21; 66) = 2.36). AqF (100 mg/ml) shifted to the right the CaCl 2 concentration-effect curve, increasing the EC 50 from 2170 ± 112 to 2690 ± 132 mM (n = 3, p < 0.001, F calc = 220.80 ; F (0.01; 29; 60) = 2.19). L-NAME (100 mM) did not modify the AqF inotropic effect (n = 3, p > 0.05) sugesting that the oxide nitric pathway did not participate of the action mechanism of AqF. We can conclude that AqF depresses the atrial contractile by reducing the calcium entry in myocardial cells and also by openenig potassium channels of cardiac tissue. Uniterms:Psidium guajava/acetic extract/ inotropic effect. Inotropic effect/experimental study. Myocardium/contraction/experimental studies. Myocardial cells/experimental studies.O efeito inotrópico da fração aquosa (AqF) do extrato acético das folhas de Psidium guajava L. foi investigado em átrio esquerdo de cobaia. A força miocárdica foi medida isometricamente (27 ± 0,1 o C; 2 Hz). A AqF (100 mg/mL) reduziu a contratilidade em até 85 ± 9,4 % (n = 4; p < 0,001; F calc = 51,70; F (0,01; 4; 21) = 5,09; CE 50 = 14,28 ± 3 mg/mL) de forma dependente da concentração. Este efeito foi reduzido pelo tetraetilamônio (TEA, 20 mM) que também aumentou a CE 50 de 14,28 ± 3 mg/mL para 50 ± 7 mg/ mL (n = 4; p < 0,001; F calc = 282,13; F (0,01; 21; 66) = 2,36). A AqF (100 mg/mL) deslocou para a direita a curva concentração-efeito do CaCl 2 , aumentando a CE 50 de 2170 ± 112 para 2690 ± 132 mM (n = 3; p < 0,001; F calc = 220,80 ; F (0,01; 29; 60) = 2,19). Por outro lado, o L-NAME (100 mM) não alterou o efeito inotrópico da AqF (n = 3; p > 0,05), sugerindo que a via do óxido nítrico não participa do mecanismo de ação da AqF. Conclui-se que a AqF deprime a contratilidade atrial por reduzir a entrada de cálcio nas células miocárdicas e por abrir canais de potássio deste tecido. Unitermos:Psidium guajava/extrato acético/efeito inotrópico. Efeito inotrópico/estudo experimental. Miocárdio/contração/estudo experimental. Células miocárdicas/estudo experimental. INTRODUCTIONPsidium guajava L (Myrtaceae), commonly called guava ("goiaba" in Brazil), is widely found in the whole world. Teas prepared from its leaves are commonly used to treat colic, diarrhea, cough, gingivitis, scurvy, uterine bleedings, bronchitis, arterial hypertension, and some intestinal parasitosis (Coe, Anderson, 1996;Ramirez et al., 1988). The following effects of P. guajava leaf extracts were reported: slowed locomotion (Lutterodt, Maleque, 1988), depression of the central nervous system (Ol...

Platelet inhibitory effects of juices from Pachyrhizus erosus L. root and Psidium guajava L. fruit: a randomized controlled trial in healthy volunteers

“…Our results also demonstrated the cardiac depressive effect of GF juice intake. Similarly, guava leaf extract was previously demonstrated to have cardiac depressant activities in the cardiac tissue [ 27 ] and animal model [ 56 ]. Overall, the apparent limitation of our study is using a relatively small number of subjects per group which might lead to the arbitrary generalization of study outcome.…”

“…Antihypertensive effect of guava fruit (GF) on spontaneous hypertensive rats was previously demonstrated [ 25 ]. Studies using guava leaf extract showed cardio-protective effects against myocardial ischemia-reperfusion injury in the isolated rat heart [ 26 ] and cardio-inhibitory action in rats and guinea pig models [ 27 ].…”

Phytochemical investigation on various parts of Psidium guajava

“…The leaves and barks of guava is used as a cure of diarrhea (Ojewole et al, 2008), sore throat, vomiting, stomach upset, vertigo etc. In a recent study with guinea pigs Brazilian researches reported that guava leaf extract has numerous effect on cardiovascular system (Gondim, 2009). Other animal studies showed that guava leaf extracts have analgesic, sedative and CNS depressant activity.…”