Evaluation of the antinociceptive activities of the aqueous root extract of Alchornea cordifolia (Schumach and Thonn) Müll. Arg. (Euphorbiaceace)

Summary. Alchornea cordifolia (Schumach and Thonn) Müll. Arg. (Euphorbiaceace) is used in traditional African medicine for the treatment of painful and inflammatory disorders. This study was carried out to investigate the antinociceptive effect of aqueous root extract of Alchornea cordifolia in mice. The antinociceptive activity of the oral doses of 100 – 400 mg/kg of Alchornea cordifolia was assessed using the acetic acid-induced mouse writhing reflex, formalin-induced paw licking, hot plate and tail clip models of pain.The extract (100–400 mg/kg) produced significant (P< 0.05) dose dependent inhibition of writhing reflex as well as significant dose-dependent inhibition of the neurogenic and inflammatory pains associated with the formalin test. The formalin test result showed that the extract (100-400 mg/kg, p.o) increased pain threshold in a dose dependent manner in both phases but the effect is more prominent against the inflammatory phase (second phase).This findings showed that A.cordifolia possesses both central and peripheral analgesic activity, as shown by its ability to significantly (p<0.05) inhibit nociceptive response associated with both phases. The ability of the oral doses of the extract (100-400 mg/kg) to prolonged the reaction time of the animals to noxious heat in hot plate and tail clip models of pain, in a dose dependent manner suggests a central analgesic effect. Acute toxicity studies of oral doses of aqueous root extract of Alchornea cordifolia in mice revealed that it has a wide margin of safety as it well tolerated by the animals.The results of the study suggest an analgesic property demonstrated by the aqueous root extract of Alchornea cordifolia possibly mediated by central and peripheral mechanisms and thus confirm the folkloric uses of the plant in painful disorders. Industrial relevance. In the recent past there has been a growing interest in Traditional medicine/Complementary and Alternative Medicine (TCAM) and their relevance to public health both in developed and developing countries. Diversity, flexibility, easy accessibility, broad continuing acceptance in developing countries and increasing popularity in developed countries, relative low cost, low levels of technological input, relative low side effects and growing economic importance are some of the positive features of traditional medicine. In this context, there is a critical need to mainstream traditional medicine into public health care to achieve the objective of improved access to healthcare facilities. Medicinal plants are largely used worldwide by the populat