Abstract

Previous works on the stem bark of Musanga cecropioides R. Brown (Moraceae) reported the hypotensive effects of aqueous extract at 10 - 40 mg/kg. This present work was carried out to examine the hypotensive effects of 3, 4-dihydroxybenzaldehyde isolated from the stem bark. Using pentobabitone sodium anaesthetized normotensive rabbits; the effects of the compound on blood pressure were tested at doses of 2.5 - 10 mg/kg. Also, the probable mechanism of action of the compound was examined using atropine, promethazine and the direct effect of the compound on isolated heart. At 2.5 mg/kg, the compound lowered the arterial blood pressure by 12.61 ± 2.45 mmHg. The blood pressure was further lowered by 17.88 ± 0.73 mmHg at 10 mg/kg. The hypotensive effect of the compound was observed to be unaffected by prior administration of either atropine (0.5 mg/kg) or promethazine (0.25 mg/kg). Similar to the mechanism of action of the crude aqueous extract, 3, 4-dihydroxybenzaldehyde induced negative inotropic and chronotropic effects on the heart as it dose-dependently reduced the force and rate of contractions of the heart from 0.5 - 2 mg/ml. The reductions observed at 1 mg/ml were effectively reversed by 10 μg/ml adrenaline. However, the effects of 2 mg/ml were not reversed by administration of the adrenaline. The compound seems to be one of the constituents responsible for the hypotensive effect of the aqueous extract of M. cecropioides stem bark earlier reported. 

Key words: Hypotensive effects, Musanga cecropioides, stem bark, 3, 4-dihydroxybenzaldehyde.