Objectives: This study was carried out to investigate the indicators of acute toxicity, anti-nociceptive, anti-inflammatory and phytochemical properties of the ethanol leaf extract of Uraria picta (UP) in rodents.
Methods: The acute toxicity indicators via oral and intraperitoneal routes as well as acute spontaneous motor toxicity in the open field test were conducted in mice. For the anti-nociceptive tests, the acetic acidinduced writhing and formalin tests were conducted in mice, while the carrageenan induced paw oedema and, wet and dried cotton pellet-induced granuloma formation tests in rats were applied for the antiinflammatory tests. Mechanisms of action of the anti-nociceptive actions were also explored using treatment interactions with naloxone, metergoline, glibenclamide, sulpiride and NG–nitro-L-arginine.
Results: The acute oral toxicity test did not record any mortality in mice up to 5g/kg, but the i.p. administered UP produced LD of 812.83 mg/kg; moreover, the i.p., but not orally administered UP, from 50 500 mg/kg, produced dose-dependent significant (p<0.05) decrease in number of line crosses as well as rearing behaviour. For anti-nociceptive action, a significant (P<0.05) inhibition of acetic acid induced writhing, and reduced duration of paw-licking in the formalin induced test in mice was produced by UP (25-100 mg/kg, p.o.). In the anti-inflammatory activity, UP caused significant (P<0.05) dose-dependent inhibition of edema development in carrageenan induced inflammation and cotton-pellet induced granuloma formation in rats. Furthermore, pre-treatment of mice with naloxone, glibenclamide or NG–nitro-L-arginine prevented UP-induced antinociception in the mouse writhing test.
Conclusion: The findings in this study suggest that the ethanol leaf extract of U. picta is orally safe, possesses anti-nociceptive action mediated via the opioid, ATP-sensitive K+ channels and nitric oxide mechanisms; as well as anti-inflammatory activities via COX-2 mediated stabilization of lysosomal membrane and inhibition of the migration of the inflammatory cells. These justify the use of the extract as an orally safe remedy in Traditional African Medicine for the treatment of pain and inflammation, and with antioxidant properties.