The effects of methanolic extract of Marrubium vulgare L. on isoproterenol-induced acute myocardial infarction in rats

Abstract

Background- Marrubium vulgare (Lamiaceae) is a popular medicinal herb that previous studies have demonstrated its anti-inflammatory and antioxidant properties. Aim- The present study was designed to investigate the cardioprotective effect of the methanolic extract of M. vulgare against isoproterenol-induced acute myocardial infarction (MI) in rats. Methods- The aerial parts of the plant were extracted with methanol by maceration and subjected to colorimetry to determine flavonoids and phenolic compounds. High-performance TLC analysis and subsequent TLC scanning were performed to quantify the extract marrubiin content. Free radical scavenging activity was determined using 1,1-diphenyl-2-picryl-hydrazil (DPPH) test. Male wistar rats were assigned to six groups of control, sham, isoproterenol, and treatment with 10, 20, and 40 mg/kg/12h of the extract given orally concurrent with MI induction. Isoproterenol injection (100 mg/kg/day S.C.) for 2 consecutive days was used to induce acute MI. Results- Preliminary HPTLC analysis of the extract revealed the presence of marrubiin with Rf value of 0.82 as the major compound in the M. vulgare extract. Marrubiin was quantified as 156 mg per gram of M. vulgare extract. The amount of total phenolic and flavonoids contents for M. vulgare were determined as 60.4 mg gallic acid equivalent and 12.05 mg quercetin equivalent per each gram of the extract, respectively. The RC50 (reduction concentration of 50%) values of methanolic extract of M. vulgare and quercetin (as a standard free radical scavenger) were obtained as 8.24 and 3 µg/ml, respectively, from DPPH test. Isoproterenol injection exhibited changes in the electrocardiogram (ECG) pattern including ST-segment elevation and suppressed R-amplitude. All doses of the extract significantly amended the ECG changes (p<0.001). A severe myocardial necrosis, fibrosis and edematous along with a sharp reduction in the arterial blood pressure, left ventricular contractility (LVdP/dtmax), and relaxation (LVdP/dtmin), but a marked increase in the left ventricular end-diastolic pressure (LVEDP) were seen in the isoproterenol group. All parameters were significantly improved by the extract treatment. The extract (10 mg/kg) strongly (p<0.001) increased LVdP/dtmax from 2750±309 (mmH/sec) in the infracted myocardiums to 5391±377. Similarly, treatment with 40 mg/kg of M. vulgare lowered the elevated LVEDP from 19±1.2 mmHg to a normal value of 6.4±1.7 (p<0.001) and the heart to body weight ratio from 4.14±0.05 to 3.48±0.08 (p<0.001). In addition to in vitro antioxidant activity, the extract suppressed markedly (p<0.001) the elevation of malondialdehyde levels both in serum and myocardium by 50-65 %. In the groups treated with 10, 20 and 40 mg/kg of M. vulgare extract serum Creatine Kinease-MB was subsided by 55.4%, 52.2% and 69%, respectively. On the other hand treatment with M. vulgare extract greatly reduced the proinflammatory responses, as evidenced by a marked reduction (p<0.001) in the myocardial myeloperoxidase activity from 4605.2±130.98 mU/g tissue in MI group to 2946.93±303 after oral administration of the extract (40 mg/kg). The levels of TNF-α was also declined from 406.15 ± 27.8 pg/ml in the serums of MI group to 100±12.2 (P < 0.001) in the group treated with 10 mg/kg of extract. In addition, peripheral neutrophil count that was elevated (p < 0.001) from 13±2.6% in normal control to 33.4±4.8% by isoproterenol injection, was significantly lowered by all doses of the extract (p < 0.001). Conclusion- Our results suggest that M.vulgare has strong protective effect on MI and these cardioprotective effects can be related to its antioxidant and anti-inflammatory properties.