Phytochemical screening and evaluation of cardioprotective activity of ethanolic extract of Ocimum basilicum L. (basil) against isoproterenol induced myocardial infarction in rats

Abstract

Background and the purpose of the study: The objectives of the present study were phytochemical screening and study of the effects of ethanolic extract of aerial parts of Ocimum basilicum (basil) on cardiac functions and histopathological changes in isoproterenol-induced myocardial infarction (MI).

Methods: The leaves of the plant were extracted with ethanol by maceration and subjected to colorimetry to determine flavonoids and phenolic compounds. High-performance TLC analysis and subsequent CAMAG's TLC scanning were performed to quantify rosmarinic acid content. Wistar rats were assigned to 6 groups of normal control, sham, isoproterenol, and treatment with 10, 20, and 40 mg/kg of the extract two times per day concurrent with MI induction. A subcutaneous injection of isoproterenol (100 mg/kg/day) for 2 consecutive days was used to induce MI.

Results: Phytochemical screening indicated the presence of phenolic compounds (5.36%) and flavonoids (1.86%). Rosmarinic acid was the principal phenolic compound with a 15.74% existence. The ST-segment elevation induced by isoproterenol was significantly suppressed by all doses of the extract. A severe myocardial necrosis and fibrosis with a sharp reduction in left ventricular contractility and a marked increase in left ventricular end-diastolic pressure were seen in the isoproterenol group, all of which were significantly improved by the extract treatment. In addition to in-vitro antioxidant activity, the extract significantly suppressed the elevation of malondialdehyde levels both in the serum and the myocardium.

Conclusion: The results of the study demonstrate that Ocimum basilicum strongly protected the myocardium against isoproterenol-induced infarction and suggest that the cardioprotective effects could be related to antioxidative activities.

Figure 1

Photodensitogram of the fluorescent HPTLC plate of rosmarinic acid (densitograms 1–8, from front to back, affording 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 μg rosmarinic acid) and O. basilicum ethanolic extract (densitograms from 9–14, affording 20, 40, 60, and 80 μg of the extract) depicted by TLC scanner 3(CAMAG) in which the X, Y and Z axis represents RF of each detected spot, height of the peaks (Spot’s density), and location on the plate, respectively.

Figure 2

Effect of the hydroalcoholic extract of O. basilicum (OB) on electrocardiographic patterns and changes (recorded from limb lead II) in normal control, isoproterenol alone injected (MI), and treated rats. Values are mean ± sem (n = 6). ^aP < 0.001 from respective control value; ^***P < 0.001 as compared with isoproterenol treated group using one way ANOVA with Student-Newman-Keuls post hoc test.

Figure 3

Left ventricular maximal and minimal rates of pressure increase (LV dP/dt_max; LV dP/dt_min) in the control group and in the rats treated with isoproterenol alone (rats with myocardial infarction), O. basilicum extract alone (sham), and isoproterenol plus O. basilicum extract. Iso: isoproterenol; OB: O. basilicum extract. Values are mean ± sem (n = 6). ^ap < 0.05; ^bp < 0.001 from respective control value; *p < 0.05, **p < 0.01, ***p < 0.001 as compared with isoproterenol treated group using one way ANOVA with Student-Newman-Keuls post hoc test.

Figure 4

Photomicrographs of sections of rat cardiac apexes. Heart tissue of a rat subcutaneously injected with isoproterenol alone shows intensive cardiomyocyte necrosis and increased edematous intramuscular space. Treatment with O. basilicum extract demonstrates a marked improvement. Iso: isoproterenol; OB: O. basilicum extract. H&E (40 M).

Figure 5

Heart tissue of a rat treated with isoproterenol shows an intensive fibrosis (blue spots are shown by arrows) and angiogenesis. Pretreatment with O. basilicum extract significantly prevented the fibrosis. Iso: isoproterenol; OB: O. basilicum extract. Gomeri's one-step Trichrom method (40 M).

Figure 6

The effects of oral administration of hydroalcoholic extract of O. basilicum extracrt on grading of histopathological changes in rats’s cardiac apex tissues (scors 1, 2, 3, and 4 show low, moderate, high and intensive pathological changes, respectively). Data are expressed as mean ± sem (n = 5-6). ^ap < 0.001 from respective control value; *p < 0.05; **p < 0.01; ***p < 0.001 as compared with isoproterenol treated group using one way ANOVA with Student-Newman-Keuls post hoc test.