Effects of extracts from flowering tops of Crataegus meyeri A. Pojark. on ischaemic arrhythmias in anaesthetized rats.

Different species of Crataegus, commonly called Hawthorn, were reported to possess wide pharmacological effects on the cardiovascular system. In the present study, chloroform, ethylacetate and methanol (70%) extracts of the flowering tops of Crataegus meyeri A. Pojark. were studied. The extracts were tested on the incidence and severity of arrhythmias induced by a period of myocardial ischaemia in open-chest anaesthetized male Wistar rats. Infusion of a hydroalcohol extract (1 mg/kg/min) resulted in a significant decrease in the total number of ventricular ectopic beats (from 1494 +/- 362 in the control to 634 +/- 102), mainly by reduction of beats occurring as ventricular tachycardia. A chloroform extract (1 mg/kg/min) also reduced the total number of ventricular ectopic beats but this reduction was due to the decrease of single extrasystoles. A significant reduction in the time spent for ventricular fibrillation was seen by the hydroalcohol and ethylacetate extracts. There were no significant changes in the heart rate and blood pressure during the extract infusion. However, bolus injection of all the extracts caused a significant reduction in the blood pressure. Thus, the extracts of Crataegus meyeri have a hypotensive and a potential antiarrhythmic action on ischaemic myocardium and may possess active principles. Copyright 2000 John Wiley & Sons, Ltd.