Blood pressure lowering action of active principle from Ocimum basilicum

Ocimum basilicum belongs to the family Labiatae and commonly is known as Basil (Tulsi). It is a widespread plant cultivated in the world. In Indo-China, the ashes of the roots are suggested as a remedy for skin disease. The plant is used as aromatic, anti-microbial, astringent in dysentery, while the leaves are antipyretic. The seeds are laxative, particularly in case of habitual constipation. The juice of the leaves and flowers are a treatment of cough. A decoction may be given after parturition as emmenagogue and febrifuge. The leaves are carminative, antispasmodic and sedative. Preparations of basil are used for supportive therapy for feeling of fullness and flatulence, for the stimulation of appetite and digestion, and as diuretic.

In anaesthetized rats, methanolic extract, fractions, and pure compound eugenol (0.3–3.0mg/Kg) produced dose-dependent fall in blood pressure and heart rate. These effects were not blocked by atropine (1mg/Kg) and eugenol did not modify presser response of norepinephrine which rules out the possibility of cholinergic stimulation or α-adrenergic blockade. In spontaneously beating atria, eugenol caused decrease in force and rate of contractions. These effects remain unaltered in presence of atropine. In rabbit aorta, eugenol caused relaxation of norepinephrine and potassium induced contractions in a concentration-dependent manner. These results suggest that the direct relaxant action of eugenol on myocardium and on blood vessels may be responsible for its hypotensive and bradycardiac effects observed in the in vivo studies.