Analgesic and anti-inflammatory activity of the aqueous leaf extract of <i>Piliostigma thonningii</i> (Caesalpinoideae)

Abstract

The leaves of Piliostigma thonningii (Schum) have been used in herbal medicine to arrest bleeding, as laxatives, to treat fevers, bacterial infection and inflammation. In order to provide scientific justification for the ethnomedical uses of the leaves, the study was designed to investigate the analgesic and anti-inflammatory activity of the extract and its possible mechanism of action. Analgesic activity was examined using the tail immersion and acetic acidinduced writhing test while acute anti-inflammatory effect was studied using xylene-induced ear edema model. The extract significantly (p<0.05) decreased the number of writhes in the mice at 200 and 400 mg/kg doses of the extract with 54.95 and 56.53% inhibition respectively but did not show any significant effect (p>0.05) in the tail immersion test when compared to the control. There was a significant decrease (p<0.001) in ear oedema induced by xylene by 200 and 400 mg/kg of the extract with 83.06 and 90.55% inhibition respectively. Oral acute toxicity assays did not show any mortality at 10 g/kg of the plant extract. The inhibition of acetic acid-induced writhing in
mice by extract suggested that its analgesic affect maybe be peripherally mediated and the inhibition of edema suggests a likely indication of the antiphlogistic effects of the extract. In conclusion, the leaf extract of P. thonningii possesses anti-inflammatory and analgesic properties which may be mediated via peripheral inhibiting mechanisms. These results thus justify its use in the treatment of pain and inflammatory conditions in tradomedical practice.

Keywords: Piliostigma thonningii; anti-inflammatory; analgesic