Cardioprotective Effects of Rosmarinic Acid on Isoproterenol-Induced Myocardial Infarction in Rats

Background: Rosmarinic acid is a polyphenolic compound with considerable antioxidant activities. We aimed to investigate its cardioprotective effects against isoproterenol-induced myocardial infarction (MI) in rats. Methods: Male Wistar rats were assigned to 5 groups of control, isoproterenol, and treatments with 10, 20, 40 mg/kg of rosmarinic acid. Myocardial infarction was induced by subcutaneous injection of isoproterenol (100 mg/kg) once daily for 2 days. Rosmarinic acid was injected intraperitoneally once daily for 4 days, from the day of isoproterenol injection. In the fifth day the animals were anesthetized and hemodynamic and electrocardiographic parameters were recorded. After collecting the blood samples, the hearts were removed, weighed immediately to measure the cardiac enlargement, and kept for further histological studies. Lactate dehydrogenase and malondialdehyde were measured in the heart tissues for evaluating the damages and lipid peroxidation, respectively. Results: Rosmarinic acid revealed a considerable antioxidant activity in vitro, with IC50 of 6.43µg/ml. Isoproterenol induced cardiac arrhythmias, myocardial damage and cardiac enlargement. Rosmarinic acid significantly reduced peripheral neutrophil percentage and inhibited isoproterenol-induced ST-segment elevation and R-amplitude depression in the infarcted hearts. It also significantly increased the mean arterial pressure and heart rate and decreased the left ventricular end diastolic pressure. The ventricular contractility was considerably improved by rosmarinic acid. Histopathological evaluations showed that rosmarinic acid significantly diminished the post-MI necrosis and fibrosis in the myocardium and inhibited the cardiac edematous. Conclusion: It is deducible from the results that rosmarinic acid improves the cardiac performance and inhibits post-MI myocardial depression, probably due to its anti-oxidative activity.