Author(s): John K Muchonjo, James M Mbaria, Joseph M Nguta and Gervason A Moriasi

Abstract: Pain is the most widely diagnosed and managed symptoms of human diseases, with various debilitating effects. Current analgesics agents have shown low efficacy, are inaccessible, unaffordable, and elicit deleterious side effects which limit their use, thereby warranting the need for alternative and complementary strategies. Mystroxylon aethiopicum is widely utilized in the Agikuyu community of Kenya to treat stomachache, chronic pain, coughs, among other conditions; however, its analgesic efficacy and safety data are scanty, hence the present study. The analgesic activity of the aqueous and methanolic stem bark extracts of M. aethiopicum were determined using the standard acetic acid-induced writhing technique. Further, qualitative phytochemical screening for various phytocompounds in the studied plant extracts was done following standard phytochemical screening methods. The aqueous and methanolic extracts of M. aethiopicum possess noteworthy analgesic activity as demonstrated by the higher percentage inhibitions of writhing in the treated mice; however, the aqueous extract exhibited significantly lower analgesic efficacy than the methanolic extract (P<0.05). Qualitative phytochemical screening revealed presence of antioxidant-associated compounds including phenols, flavonoids, terpenoids, among others, which exhibit analgesic activity. All the studied plant extracts did not cause acute oral toxicity effects in experimental mice, hence safe (LD₅₀>2000 mg/Kg bw). The specific mechanisms of analgesic action, the responsible compounds should be elucidated. Moreover, extensive toxicological studies involving the studied plant extracts should be conducted to fully profile and assure their safety.