ABSTRACT
Aim: To investigate anti-inflammatory and antinociceptive potentials of aqueous stem bark extract of Khaya senegalensis A. Juss (Meliaceae) in rodents. Methodology: Anti-inflammatory activity of aqueous stem bark extract of K. senegalensis (AKS) was studied in different models. Effect of the extract in acute inflammation was tested in carrageenan-induced rat paw edema and its effect in chronic inflammation was evaluated using cotton pellet-induced granuloma test. Croton oilinduced ear edema in mice was used to investigate the effect of the extract on topical inflammation. Antinociceptive property of AKS was evaluated using three models of nociception: hot-plate test, acetic acid-induced writhing in mice and formalin-induced paw licking in rats. Membrane stabilizing effect of AKS was tested in heat and hypotonicity-induced hemolysis. The mechanism of antinociceptive effect of the extract was evaluated by pre-treating rats with metoclopramide, a dopamine (D2) antagonist (1.5 mg/kg body wt.) and naloxone, an opioid receptor antagonist (5 mg/kg body wt.). One hour after these treatments, the rats were given AKS (150 mg/kg p.o) and their reaction time in hot-plate was assessed. Free-radical scavenging activity of the extract was measured by decrease in the absorbance of 1, 1-Diphenyl-2-picrylhydrazyl (DPPH) methanol solution. Results: The extract produced significant (P<0.05) and dose-dependent inhibition of ear edema in mice. It also caused a significant (P<0.05) reduction in granuloma formation and paw edema in rats. At concentration range of 125 - 500 μg/ml, AKS significantly (P<0.05) protects the erythrocyte membrane against lysis induced by heat and hypotonic medium. It also significantly (P<0.05) reduced the licking/biting time of the formalininjected rat paw in the early (19 - 51 % reduction) and late (13 - 57 % reduction) phases. The extract demonstrated significant (P<0.05) antinociceptive activity in the hot-plate and writhing tests and exhibited good scavenging effect on DPPH free radical. Conclusion: The study demonstrated that Khaya senegalensis stem bark aqueous extract possesses anti-inflammatory activity and antinociceptive effect mediated via central and peripheral mechanisms. Further studies on the plant may produce lead molecules for the development of new anti-inflammatory drugs.