FABIAN C. AMAECHINA

Background: The blood pressure-lowering effect of aqueous leaves extract of Phyllanthus amarus has been reported in earlier work in normotensive albino rabbits. The effects of organic solvent fractions were evaluated in Wistar rats.
Methods: The aqueous fraction obtained from the crude extract of the leaves was evaluated for blood pressure-lowering effect in anaesthetized normotensive Wistar rats, at the graded doses of 2.5-40 mg/kg after which it was subjected to vacuum liquid chromatography (VLC) using combinations of chloroform, ethyl acetate, methanol and water. This yielded eleven fractions which were bulked into six samples (A-F) after thin layer chromatograph analysis, and samples A, B and C were evaluated for activities on the blood pressure of hypertensive Wistar rats at the graded doses of 5 to 20 mg/kg. Fraction “C” showed the highest blood pressure lowering effect and was further subjected to column chromatographic and VLC analysis, to obtain fraction (BVLC2) which was evaluated for possible blood
pressure lowering effect in hypertensive Wistar rats.

Results: The aqueous fraction caused a dose dependent decrease in the blood pressure of normotensive Wistar rats, decreasing the mean arterial blood pressure (MAP) from a basal level of 104.58 ± 8.29 mmHg to 45.22 ± 6.71 mmHg (p<0.0001; 66.4%) at the dose of 40 mg/kg. Fraction “C” caused significant decrease in the MAPfrom 116.99 ± 10.28 mmHg to 68.33 ± 6.78 mmHg (p < 0.001; 0.01%) at the dose of 20 mg/kg, while the fraction BVLC2 decreased the MAPfrom 146.11 ± 8.29 mmHg to 79.33 ± 6.18 mmHg (***p< 0.001) at the dose of 10 mg/kg, indicating a trend of increasing potency along the course of purification.

Conclusion: The aqueous fraction of the leaves of Phyllanthus amarus yielded column chromatographic sample (BVLC2), that might possibly serve as a lead sample from which pure active hypotensive constituent(s) could be isolated.

There is already a literature report on the anti-ulcer effect of water extract of Ficus exasperata. Some communities in Edo and Delta States of Nigeria use the decoction of the leaf as hypotensive crude drug. Verification of this claim and also the microscopy and other pharmacognostic parameters which can be used to establish the identity of the leaf were carried out. The microscopy of the leaf powder revealed the presence of straight walled epidermal cells, cone or nail shaped trichomes or epidermal hairs, clustered or prismatic calcium oxalate crystals of varying dimensions. The percentage weight loss on drying was 9.84 ± 0.08 whereas water and alcohol extractive values were 5.29 ± 0.07 and 2.21 ± 0.11, respectively. The ash value was 30.68 ± 0.44 whereas the acid insoluble ash and water soluble ash values were 17.87 ± 0.37 and 16.73 ± 0.13, respectively. Preliminary phytochemistry of leaf showed that it contains tannins, flavonoids and saponins with no traces of alkaloids or anthraquinones. The water extract showed a dose related reduction in mean arterial blood pressure. At 10 mg/kg, a reduction of 16.6 ± 1.1mmHg was observed, whereas at 30 mg/kg, a fall in mean arterial pressure of 38.3 ± 0.6 mmHg was obtained. The hypotensive effect of the extract was significantly reduced with a prior administration of 2.5 mg of either atropine or chlorpheniramine. This suggests the probable stimulation of muscarinic receptors in the heart or release of histamine into the circulatory system thereby causing the initial fall in blood pressure.