The Antimalarial Effect and Mechanism of Action of Methanolic Root Extract of Boerhaavia diffusa in Mice

Aims: This study evaluated the antimalarial effect of methanolic root extract of Boerhaavia diffusa and its mechanism of action in Mice.

Study Design: One-factor two control groups experimental design.

Place and Duration of Study: Department of Pharmacology, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria, between October 2012 and May 2013.

Methodology: The crude methanolic root extract of the plant was tested for its in vivo anti-plasmodial activity against Plasmodium berghei NK 65 (chloroquine resistant strain) using the three malaria models; suppressive, curative and prophylactic tests. Six different groups of albino mice of both sexes weighing 18 – 20 g (n=5 or 6) were randomly selected for the study. Group 1 was the control (normal saline, 10 ml/kg, p.o.), group 2 was the positive control (chloroquine, 10 mg/kg, p.o.), groups 3, 4 and 5 were treated with methanolic root extract at 125, 250 and 500 mg/kg, p.o., respectively, while group 6 was Nifedipine (15 mg/kg). The method of calcium colorimetry was also adopted for assaying the mechanism through which the extract acted.

Results: B. diffusa displayed antimalarial activity at all dose levels in all the three models, though optimum activity of the extract was displayed at the lowest dose (125 mg/kg) in suppressive and prophylactic models and at day 10 in curative model. The dose of 500 mg/kg had the highest activity at day 9 in curative model. The dose of 125 mg/kg again showed the best antipyretic effect in suppressive model at day 3 and this corresponds to its antimalarial activity. At 500 mg/kg, the extract lowered plasma calcium level better than the positive control (1.043 mmol/L compared with 1.35 mmol/L for nifedipine).

Conclusion: The methanolic root extract of B. diffusa possessed antimalarial and antipyretic effects which confirm its folkloric use in the treatment of malaria and fever.