To evaluate the possible analgesic properties of the methanol leaf extract of Alstonia boonei
(De Wild, Apocynaceae) a locally available plant used in traditional medicine for the management of
pain and other conditions.
leaves were extracted with methanol. Rodent models were employed in
screening the analgesic effect of the extract. Pain indices evaluated in hot plate and tail flick tests,
formalin pain test and mouse writhing assay were mean reaction time to latent heat, time spent in licking
of injected paw and abdominal writhes, respectively.
Oral administration of the extract caused a significant (p < 0.05) dose-dependent reduction in
the number of abdominal writhes (control, 84.67 ± 9.58; 100 mg/kg, 57.86 ± 3.07; 200 mg/kg, 24.40 ±
3.92; and 400 mg/kg, 22.50 ± 2.53). The extract also produced significant (p < 0.05) but non-dose
dependent increase in elevation of pain threshold in the hot plate (ranging from 27.99 to 42.26 %
inhibition) and tail flick tests (ranging from 34.73 to 81.42 % inhibition) in mice and rats, respectively. All
doses of the extract used produced significant (p < 0.05) inhibition of both phases of the formalininduced
pain in mice, with a more pronounced anti-inflammatory effect on the late (ranging from 46.96 to
74.12 %) phase than the early anti-neurogenic (ranging from 49.52 to 51.47 %) phase.
The results obtained suggest that the analgesic effect of Alstonia boonei
may be mediated
via both central and peripheral mechanisms.