ABSTRACT
Phyllanthus amarus is a small herb that is indigenous to the rainforest of the tropical and subtropical areas throughout the world. Various African communities use the plant to treat such ailments as diabetes mellitus, hepatitis infection, stomach ache, dysentery, and jaundice. The plant has been reported to possess hypotensive, diuretic and analgesic properties.
The dried powdered leaf was extracted with distilled water using soxhlet apparatus. The extract was tested on albino mice for anticonvulsant and sedative effects, and on albino rats for barbiturate induced sleeping time. The effect of graded doses (5-80mg/kg) of the extract on blood pressure was investigated, using normotensive adult albino rabbits. The effects of the extract on isolated rabbit heart and on isolated rat portal vein were also investigated.
The extract provided complete protection at the two doses (100mg/kg and 200mg/kg) to the mice against maximal electroshock-induced convulsion. The extract provided a minimal protection to the mice against pentylenetetrazol-induced convulsion, at the dose of 500mg/kg, of 20%.
The extract neither had sedative effect, nor impaired motor coordination at the two doses (100mg/kg and 200mg/kg) that protected against maximal electroshock-induced convulsion, and did not influence barbiturate-induced sleeping time.
The extract caused a graded dose (5-80mg/kg) dependent fall in the mean systolic, diastolic and mean arterial pressures in normotensive rabbits. The dose of 5mg/kg had the least hypotensive
effects, causing a fall in the mean diastolic, systolic and mean arterial pressures of 19.7±5.4, 13.3±3, and14.7±3.4 respectively, while the dose of 80mg/kg caused the greatest fall in systolic, diastolic, and mean arterial pressure of 55.5±9.5, 49.7±7.9, and 48.0±6.54 respectively. Atropine (1mg/kg) blocked the hypotensive effect of the extract in a competitive manner. The extract had a concentration dependent depressant effect on the force and rate of contraction of the isolated heart of rabbit, with greater reduction on the rate than the force of contraction. The extract was also found to inhibit the myogenic contractions of the isolated portal vein of rat, also in a concentration-dependent manner.
It is therefore concluded that the extract of the leaves of Phyllanthus amarus has an anticonvulsant effect, did not sedate the animals nor impair their motor coordination ability. It is also concluded that the extract lowers blood pressure in normotensive rabbits, which may be by the combined effect of vascular smooth muscle relaxation and by a depressant effect on the force and rate of myocardial contraction.
