The stem bark of Piptadeniastrum africanum (Hook. F.) (syn. Piptadenia Africana) Brenan (Mimosaceae) is used in Cameroonian and Gabonese folk medicine for the relief of some painful sicknesses. This study was intended to evaluate the analgesic and anti-inflammatory activities of the aqueous extract of P. africanum. The analgesic investigations were carried out against acute noxious stimuli, that are chemical (acetic acid-induced writhing and formalin-induced pain) and pressure tests on one hand; and on the other hand, against a chronic noxious stimulus, that is the formalin-induced hyperalgesia. For anti-inflammatory activities, the formalin-induced oedema of the hind paw of rats was used and the paw volume measured mechanically with a micrometer, during 4 hours and 9 days respectively for acute and chronic evaluation. The results were subjected to statistical analysis. The aqueous extract reduced significantly the writhing with a maximum effect of 54.35 % at the dose 125 mg/kg. It reduced equally the licking time during formalin-induced pain with maximum effects of 53.34 % and 83.80 % respectively at the first and the second phases of the test (500 mg/kg). The extract showed a significantly weak and latter activity during pressure and hyperalgesia tests. The oral administration of the aqueous extract caused significant anti-inflammatory activity on the paw oedema induced by formalin. The present results show that the stem bark of P. africanum possesses analgesic and anti-inflammatory activities, and the analgesic effect may be acting on the central and the peripheral nervous system.

Keywords: analgesic, anti-inflammatory, hyperalgesia, Piptadeniastrum africanum