Fresh leaves from V. album plant was collected and extracted using
standard methods. Acute toxicity studies showed that the crude extract
had an LD50 value of 417.5 mg/kg. mice, i.p. Based on this value, test
doses (5-160mg/kg) below the LD50 value were selected and used to
determine the effects of each dose of extract on the arterial blood
pressure (BP) and heart rate of normotensive and hypertensive rats.
Some pharmacological agents like propranolol, noradrenaline,
acetylcholine and atropine sulphate were also used to assess the
mechanism of action of the extract on blood pressure. From the results,
the extract produced a dose-dependent depression of blood pressure and
heart rate in both normo- and hypertensive rats. At doses of 5mg/kg and
160mg/kg, the extracts produced about 8.99 ± 3.2% and 54 ±
7.4% depression of BP respectively, in normotensive rats while the
corresponding values for the hypertensives were 4.8 ± 2.3% and
43.9 ± 5.5% respectively. The duration of action of the extract
was also found to be dose-dependent. Noradrenaline (1.5 μg/kg)
blocked the action of the extract. Both propranolol (1.0μg/kg) and
atropine (1.5μg/kg) failed to block or abolish the action of the
extract on rat BP. We suggest a non-adrenergic, non-cholinergic
mechanism for the action of the extract on blood pressure