Evaluation of Analgesic Property of Petroleum Ether/Ethyl Acetate Stem Bark Extract and Fractions of Maerua angolensis in Murine Models of Pain

This study investigated the possible antinociceptive action of the petroleum ether/ethyl acetate extract and fractions prepared from the stem barks of Maerua angolensis. The acetic acid-induced abdominal writhing, formalin–induced nociception, prostaglandin E2–induced mechanical hyperalgesia, bradykinin– and epinephrine-induced thermal hyperalgesia tests as well as Paw withdrawal test using Hargreaves thermal hyperalgesia model were used to assess the antinociceptive effects of the extract and the fractions after oral administration in rodents. Diclofenac and morphine were used as reference analgesic agents. Mice were submitted to the rotarod test in order to assess any non–specific muscle–relaxant effect of the extract and the fractions. The petroleum ether/ethyl acetate extract and the fractions of Maerua angolensis produced significant (P < 0.05) and dose-dependent antinociceptive effects in the acetic acid, formalin, prostaglandin E2, bradykinin, epinephrine and paw withdrawal tests. The extract and the fractions of Maerua angolensis (3 and 10 mg/kg) did not compromise the motor coordination of animals in the rotarod test, suggesting lack of central depressant effect. The petroleum ether/ethyl acetate extract and fractions of Maerua angolensis stem bark produced dose-dependent antinociception in murine models of chemical, mechanical and thermal nociception suggesting peripheral and central analgesic action.