Antinociceptive activity of various solvent extracts of Maerua angolensis DC stem bark in rodents

Abstract

Various parts of Maerua angolensis notably the leaves, roots and stem barks are used to reduce pain and also in the management of psychosis, epilepsy, and arthritis in traditional medicine. In this study, a preliminary test was performed to determine the most active plant part on the hydroethanolic extracts in the abdominal writhing test in mice. Subsequently, the stem bark, the most active plant part, was extracted with petroleum ether, ethyl acetate or hydroethanol to obtain three extracts which were tested for analgesic activity in the formalin test in rats. Animals were grouped into groups of 5 and the extracts were administered orally. Diclofenac and morphine were used as reference analgesic agents while normal saline was used for control. The leaf, root and stem bark extracts (30, 100 and 300 mg/kg) significantly (P<0.0002) and dosedependently reduced abdominal writhes induced by acetic acid with the stem bark extract being more active. In the formalin test, all the extracts (3, 10 and 30 mg/kg) significantly (P<0.0006) and dose-dependently reduced the frequency and time spent in biting/licking of injected paws in both the neurogenic and inflammatory phases induced by formalin. The petroleum ether extract was most active in neurogenic while ethyl acetate was most active in inflammatory phase. Results justify the use of the plant parts in ethnomedicine for the management of various painful conditions.