Antinociceptive activity of Euadenia trifoliolata (Schum. & Thonn.) Oliv. leaves and roots in mice.

The leaves and roots of Euadenia trifoliolata are used in Nigeria traditional medicine for the treatment of ear ache, head ache and inflammation. The aim of the study was to evaluate the antinociceptive activity of ethanolic extract of the leaves (EL) and roots (ER) of E. trifoliolata in mice. Oral toxicity testing was performed using OECD guidelines. Antinociceptive effect was studied in mice using acetic acid-induced writhing, formalin, tail immersion and hot plate tests. Total polyphenolic contents were determined using standard methods. No mortality was recorded 24 h after oral administration of both EL and ER up to 5000 mg/kg. At the dose of 50, 100 and 200 mg/kg, administration of EL and ER resulted in significant reduction in the number of writhes compared to control. The percentage inhibition of writhings was calculated as 35.67%, 46.71% and 67.94% (EL) and 55.41%, 57.32% and 72.61% (ER), respectively. In hot plate test, EL and ER showed statistically significant antinociceptive effect, although low percentage inhibition (<50%) was recorded for ER at all the doses tested. Only EL (100 and 200 mg/kg) significantly (p < 0.001) increased the reaction time in tail immersion test. Both extracts significantly (p < 0.001) reduced the licking time in both phases of formalin test compared to control. The content of total phenolic, flavonoid and proanthocyanidin varies between the two extracts and may be the basis of the observed antinociceptive effect. The results indicate antinociceptive activity for the leaves and roots of E. trifoliolata, with the extract of the leaves showing better activity.