IN VIVO EFFICACY OF METHANOLIC EXTRACTS OF ROOT AND LEAF OF Morinda lucida IN Plasmodium berghei - INFECTED MICE

Abstract

Therapeutic effects of the methanolic root extract and a combination of leaf and root extracts of Morinda lucida were evaluated for antiplasmodial activities. The phytochemical screening of the methanolic root extract showed the presence of saponins, flavonoids, alkaloids, phenolic nucleus and phlobotannins. The LD50 of the crude methanolic root extract was calculated to be 3807.89mg/kg and percentage suppression of parasitaemia was 56.30, 59.84, 67.72 and 81.80% for doses of 100, 200, 400mg/kg body weight (b.w) and 5mg/kg chloroquine respectively. Effective dose dependent inhibitions of parasitaemia were also observed in the curative test and the mean survival period in days were 15.00 ± 0.70, 18.75 ± 0.5, 19.75 ± 1.39, 23.25 ± 1.38 and 8.75 ± 1.25, for 100, 200, 400mg/kg body weight of the extract, 5mg/kg chloroquine, and untreated control respectively. Percentage prophylaxis was calculated to be 24.26, 39.41, 43.67 and 84.91% for doses of 100, 200, 400mg/kg body weight of the methanolic root extract, and 5mg/kg chloroquine respectively. The crude methanolic extract of the root was partially purified by Column chromatography to give fractions 1-4. Fractions 3 and 4, exhibited a significant curative effect in established infection. There was no significant difference at p>0.05 in antimalarial activity of fraction 4 and the crude extract. Remarkable parasitaemia inhibition by the extracts resulted into longer mouse survival relative to the control, as demonstrated in the mean survival time of the mice (29.25±1.43, 11.25±0.75, 11.75±1.60, 24.25±1.11, 28.50±1.32, 28.00±0.00 and 5.75±2.14, for crude methanolic root extract, fraction 1, fraction 2, fraction 3, fraction 4 of the crude methanolic root extract, chloroquine and control groups respectively). For the chloroquine group, two of the mice out of four used in the experiment, survived beyond 30 days. In the combination study, it was observed that, the antimalarial activity for leaf and root was slightly more, compared to that of each of the extract used singly, as seen in parasite inhibition, after 5days of treatment (26.00, 20.00, 25.28, 21.35, 27.00, 19.50, 8.5 and 85.00), for 100, 200mg/kg leaf extract alone, 100 and 200mg/kg root extract alone, 50, 100mg/kg leaf and root extracts, 5mg/kg chloroquine and control groups respectively. The effect of methanolic root extract on some serum and liver enzymes in mice infected with Plasmodium berghei were also studied. Specific activities of Glutamate oxaloacetate transaminase (GOT), Glutamate pyruvate transaminase (GPT), Alkaline Phosphatase (ALP) and Gamma glutamyl transferase (GGT) were significantly (p<0.05) high in the infected not treated group, compared to the positive control (not infected, not treated). It is concluded that the methanolic root extract of Morinda lucida is potentially useful for the development of antimalarial drug.