Effects of hawthorn, a herbal medicine, on arterial blood pressure in anaesthetized rats

Abstract

Hawthorn is a herbal medicine that has been used to treat various cardiovascular disorders. It belongs to a member of the Rosaceae family and its major components include flavonoids and oligomeric procyanidin. The present study examined the cardiovascular effects of a commercial available hawthorn extract (WS 1442) in anaesthetized rats. The carotid artery was cannulated in anaesthetized rats for blood pressure and heart rate measurement. After bolus intravenous injections of WS 1442 (3.125, 6.25, 12.5 and 25 mg/kg), mean arterial blood pressure was reduced transiently in a dose-dependent manner. A greater effect on the diastolic than on the systolic blood pressure was observed. Heart rate was not significantly affected by all doses of WS 1442. Phenylephrine (1, 3 and 10 μg/kg) dose-dependently increased arterial blood pressure. Twenty minutes after the administration of the hawthorn extract (10 and 28 mg/kg/min for 7 min), the hypertensive actions of phenylephrine was significantly reduced when compared to rats without exposure to WS 1442. From these findings, it appears that the hawthorn extract possesses hypotensive action. Pre-exposure to the hawthorn extract also resulted in an impaired response to phenylephrine, suggesting that hawthorn may have a modulatory effect on blood pressure regulation. (Supported by a CRCG grant of HKU)