Evaluation of In Vivo Antihypertensive and Ex Vivo Vasodepressor Activity of 80% Methanol Leaf Extract of Otostegia integrifolia Benth. (Lamiacae) in Rats
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Date
2018-07
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Addis Ababa Universty
Abstract
Evaluation of in vivo antihypertensive and ex vivo vasodepressor activities of 80% Methanol leaf extract of Otostegia integrifolia Benth (Lamiacae) in Rats.
Abel Degu
Addis Ababa University, 2018
Prevalence of hypertension is upsurging in the past three or four decades and it is considered as one of the major causes of morbidity and mortality via predisposing to various cardiovascular and cerebrovascular disorders. On top of that, the change in lifestyle across the globe makes the disease to be looming around on everyone. Thus, the scientific world is looking for a drug having novel mechanism of action with least side effects. To this end, there is no better inception point apart from medicinal plants which have been the major source of drug molecules with unique pharmacologic activity. In this study, the hydro-alcoholic leaf extract of Otostegia integrifolia was investigated for its in vivo antihypertensive activity using the fructose induced hypertension model and ex vivo vasodepressor activity was also assessed on thoracic aortic rings of rats. Preliminary mechanistic studies were also performed using agonists and antagonists as well as by construction of concentration-response curves. The in vivo result indicated that the extract at doses of 250, 500, and 1000 mg/kg produced a significant antihypertensive activity (p < 0.05) in all BP measurement parameters; systolic blood pressure (SBP, p < 0.05), diastolic blood pressure (DBP, p < 0.01) and mean arterial blood pressure (MAP, p< 0.001) at day 5, 10 and 15 compared to the negative controls. The extract also produced relaxation of aortic rings precontracted with high K+ (80mM) in a concentration-dependent manner. The relaxation was significant at concentrations ranging from 0.5mg/ml to 2.5mg/ml (p< 0.001). Vasorelaxant activity of the extract was not mediated through cholinergic, prostanoid, histamine, ATP-dependent K+ channel, sarcoplasmic reticulum stored Ca2+ and endothelium-dependent pathways. However, the extract shifted the Ca2+ concentration-response curve to the right and blocking of the NO/cGMP pathway only yielded 45% relaxation, suggesting that vasorelaxation could possibly be mediated via calcium channel blockade and involvement of the NO/cGMP pathway.
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Keywords
Hypertension, in vivo, ex vivo, Otostegia integrifolia, antihypertensive, vasodepressor activity