Evaluation of the Possible Mechanisms of Antihypertensive Activity ofLoranthus micranthus: An African Mistletoe

Abstract

Loranthus micranthus (LM), also called African mistletoe is a major Nigerian Loranthaceae plant used traditionally to treat hypertension. The methanolic leaf extract of the plant (LMME) has been shown to elicit anti-hypertensive activity in rats but mechanism remains unclear. This study was undertaken to study the effect of LM on pressor-induced contraction of rat aorta smooth muscles and serum lipid profiles in mice. The LMME was partitioned to produce n-butanol (NBF-LMME), chloroform (CF-LMME), ethyl acetate (EAF-LMME) and water (WF-LMME) fractions. The median effective concentrations and maximum relaxation of the fractions were determined against epinephrine and KCl pre-contracted rat aorta ring model. Serum lipid profiles and nitric oxide (NO) were determined spectrophotometrically in mice administered per orally 250 mg/kg b.w. of each fraction for 21 days. Data were analyzed statistically. NBF-LMME elicited the highest dose-dependent inhibitory effect on rat aorta pre-contracted with norepinephrine and KCl, followed in decreasing order by WF-LMME > CF-LMME > EAF-LMME. Similar order of activity was observed in the ability of these fractions to inhibit elevation in artherogenic lipids, raise serum nitric oxide and reduce cardiac arginase in mice. We conclude the anti-hypertensive activity of L. micranthus involve anti-artherogenic events, vasorelaxation, cardiac arginase reduction and NO elevation.

Loranthus micranthusLinn.: Biological Activities and Phytochemistry

“…However, higher amounts of flavonoids and oils were detected in July samples compared to April ones [29]. Iwalokun and colleagues [30] have investigated the phytochemicals such as n -butanol, chloroform, ethyl acetate, and water fractions of the methanolic extract of L. micranthus leaves of Kola nut tree ( K. acuminata ). Moderate and high levels of steroids and terpenoids were detected in n -butanol fraction, while phenolics, reducing sugars, and tannins were detected in all fractions together with moderate level for phenolics and tannins in chloroform fraction.…”

“…Indeed, methanolic extract of leaves of L. micranthus demonstrated a dose-dependent inhibition of blood pressure increase in adrenaline-induced hypertensive rat. Iwalokun and colleagues [30] studied the activity of n -butanol, chloroform, ethyl acetate, and water fraction of the methanolic extract of L. micranthus leaf harvested from K. acuminata on pressor-induced contraction of rat aorta smooth muscles. N -Butanol fraction showed the highest dose-dependent inhibitory activity (EC 50 = 0.65 mg/mL and smooth muscle relaxation of 75.2%) on rat aorta precontracted with norepinephrine and KCl, followed by decreasing order by water, chloroform, and ethyl acetate fractions.…”

“…Moderate and high abundance of steroids and terpenoids in n -butanol fraction strongly suggested that these phytoconstituents could be responsible for observed vasorelaxant and antiatherogenic activity of n -butanol fraction. Iwalokun and colleagues [30] have reviewed the possible mechanisms of antihypertensive activity of L. micranthus. …”

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“…The root was washed under running tap water followed by distilled water and dried at 40 °C in the oven for 3 days. The dried root was then pulverized into fine powder that passed through a 30-mesh sieve and stored for the future use 14 .…”

Antihypertensive efficacy of Lippia nodiflora – whole plant on uninephrectomized doca – salt hypertensive rats

“…The whole plant was washed under running tap water followed by distilled water and dried at 40⁰C in the oven for 3 days. The dried plant was then pulverized into fine powder that passed through a 30-mesh sieve and stored for the future use [19] . Preparation of Extract: The ground plant material was subsequently extracted with methanol using Soxhlet apparatus.…”