Journal of Ethnopharmacoiogy, 37 (1992) 145-149

145

Elsevier Scientific Publishers Ireland Ltd.

Experimental cardiovascular depressant effects of garlic (Allium sativum) dialysate N. Martin, L. Bardisa, C. Pantoja, R. Rom~in and M. Vargas Departamento de Cieneias Fisiolrgicas, Departamento de Farmacologia, Facultad de Ciencias Biolrgieas y de Recursos Naturales, Universidad de Concepcirn, P.O. Box 2407, Concepcirn (Chile) (Received March 1, 1991; accepted June 28, 1992)

The objectives of this work were to investigate the effects of a garlic dialysate on diastolic blood pressure (DBP), heart rate (HR) and electrocardiogram (ECG) of anaesthethized dogs and its effects on frequency and tension of isolated rat atria. Garlic dialysate led to a drop in DBP (from 112.5 ± 3.67 to 70 4- 3.16 mmHg) and a decrease in HR (from 198 4- 9.81 to 164 4- 16.59 beats/rain) in a dose-dependent manner. The ECG showed a regular sinus bradycardic rhythm. The addition of garlic dialysate to isolated left rat atria evoked a decrease in tension development. Frequency, measured by spontaneous beating of the right atria, was also reduced. Both effects were dose-dependent. In addition to these effects, the positive inotropism and chronotropism induced by addition of isoproterenol 10 -9 M, were partially antagonized by preincubation of the rat atria with the garlic dialysate. The above findings can be explained by a depressant effect on automaticity and tension development in the heart, suggesting a beta-adrenoceptor blocking action produced by the garlic dialysate.

Key words: garlic; cardiovascular effects; rat atria

Introduelion

Garlic (Allium sativum L., family Liliaceae) grows in all parts of the world and the bulb has been used extensively in both traditional and popular medicine. Interest in the study of the medical properties of this plant has increased during the last decade (Block et al., 1986; Wagner et al., 1987; Hayes et al., 1987; Feldberg et al., 1988; Mayeux et al., 1988; Pefia et al., 1988; Martin et al., 1990, 1991). In spite of the fact that there is abundant information on its chemical components and their structure, no references exist on which of these components are responsible for the multiple pharmacological actions of garlic (Laakso et al., 1988; Jansen et al., 1989; Iberl et al. 1990). We previously reported on the diuretic, natriuretic and hypotensive effects of capsules containing dried powdered garlic administered intragastrically to anaesthethized dogs, which also elicited bradycardia and T-wave inversion when administered in higher doses (Pantoja et al., 1991). Furthermore,

no references are to be found in relation to the cardiovascular effects of garlic. In the present paper we report on the hypotensive and bradycardic actions ofi.v, garlic dialysate on anaesthethized dogs and their depressant effects on isolated rat atria. Materials and Methods

Sample preparation Freshly peeled and chopped garlic bulbs (2 kg) were homogenized in double their weight of distilled water, which was then heated for 5 min at 60°C and then filtered. The filtrate was concentrated 10 times in a rotary evaporator and then dialysed (Thomas Scientific 3787-D 42 dialyser tubing, 4.8 nm pore diameter) against distilled water for 8 h. The dialysate was concentrated to 120 ml in the rotary evaporator and stored at -18°C until used. By evaporation of representative batches of the dialysate, the extract yield (w/w) was found to be 0.83%. All doses are expressed here in terms of the dry extract.

Animal preparation Correspondence to: N. Martin, Departamento de Ciencias Fisiol6gicas, Departamento de Farmacoiogia, Facultad de Ciencias Biol6gicas y de Recursos Naturales, Universidad de Concepci6n, P.O. Box 2407, Concepci6n, Chile.

Ten mongrel dogs of either sex, weighing 8-12 kg, were anaesthethized with a mixture of urethane (1 g/kg), sodium pentobarbital (3.5 mg/kg) i.p. and artificially ventilled. Arterial blood pressure was

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Fig. 1. Typical responses on arterial blood pressure (BP), heart rate (HR) and electrocardiogram (ECG) of gadic dialysate (16.8, 33.6 and 67.2 mg/kg i.v.) in anaesthetized dogs.

measured with a transducer Statham P23AC connected to the left carotid artery and recorded on a polygraph Grass 79-B. Heart rate and ECG were registered from D II ECG derivatives connected to a Harvard 350 recorder. After 10 rain of stabilization each dog was injected through the femoral vein with one dose of the garlic dialysate during 10 s. The results are expressed as mean of differences from basal controls ± S.E.M.

Isolated atria preparations Adult white rats from our laboratory, weighing 250-350 g were used. Animals were killed by a blow to the head. The heart was quickly dissected and placed immediately in preoxygenated cold Tyrode solution. Then atria were removed and mounted in a 40 ml bath f'dled with Tyrode solution mM (NaCI 137; KC1 2.7; CaCI2.21"/20 2, MgC12.6H20 0.5; NaHCO3 12; NaH2PO4.2H20 0.3 and glucose 5 g) at 36°C and oxygenated with a O2/CO2 (95:5%) mixture. Tension was registered using a Grass FT-03 transducer connectedto a Grass polygraph 79-B. The left atrium was stimulated by two gold electrodes with square pulses (14 ms, 30 V and 2 Hz) and the right was connected to a Harvard 350 recorder and was spontaneously beating. After a stabilization period of 30 rain under a load of 1 g, using a eummulative dosage schedule, dose-response curves for the

garlic dialysate were obtained. Effects were measured 30 s after the active substance was added to the bath. Results are expressed as mean ± S.E.M. Statistical analysis was performed by Student's t-test. Results

Cardiovascular experiments The i.v. injection of garlic dialysate from 16.8 mg/kg to 67.2 mg/kg produced rapid hypotensive 0-

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Experimental cardiovascular depressant effects of garlic (Allium sativum) dialysate.

The objectives of this work were to investigate the effects of a garlic dialysate on diastolic blood pressure (DBP), heart rate (HR) and electrocardio...
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