RESUMEN
Vernonia amygdalina possesses several bioactive compounds and is used in traditional medicines of southwestern Uganda, along with other regions. Its analgesic potential has not been investigated thus far. The present study examines the antinociceptive potential of the aqueous leaf extract (50-200 mg/kg) using three models of nociception (acetic acid-induced writhing, formalin test, and tail-flick test), antiplasmodial activity, and toxicology of the extract. The results show the extract significantly inhibits acetic acid-induced writhing and the formalin test in mice but did not give a potent effect in the tail-flick test, suggesting that the extract may have peripheral and central analgesic properties. The extract also exhibited significant antiplasmodial activity in mice against Plasmodium berghei with 73% inhibition in the group that received a dose of 200 mg/kg i.p. daily for 4 days. Toxicology results show no clinical signs of toxicity or adverse toxicological effects in the treated groups, except for a significant decrease in red blood cell count and a dose-dependent increase in serum bilirubin. These changes were within control values based on historical reference ranges at doses of 500-2,000 mg/kg/day for 14 consecutive days as compared to the control. This study supports the traditional use of V. amygdalina as an alternative therapy for malaria and the symptomatic relief of pain usually associated with malaria.