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Alysicarpus ovalifolius commonly known as gadagi in Northern Nigeria is claimed to possess tonic effects. Substances that show stimulant properties have demonstrated analgesic effects. This study therefore aimed at investigating the anti-nociceptive effects of the hydroethanolic extract of A. ovalifolius (HEAo) in mice and rats. The activities of the extract on acetic acid induced abdominal writhing, formalin induced pain and tail immersion test were carried out in mice. Effect on carrageenan induced pain was also determined in rats. The extract at the tested doses (100 – 400 mg/kg) significantly and dose dependently decreased the number of abdominal writhing in treated mice. Similarly, extract treated mice exhibited a decrease in the pain reaction in both phases of formalin induced algesia. Carrageenan caused hyperalgesia in rats which was ameliorated in rats treated with HEAo (400 mg/kg) when administered before and after exposure to carrageenan. Reaction time in the tail immersion test was increased in extract pre-treated mice. Results obtained from this study show that the hydro-ethanolic extract of A. ovalifolius may contain phytoconstituent probably acting on peripheral and centrally mediated pain receptors to produce anti-nociceptive actions. Key words: Anti-nociceptive effects, hydro-ethanolic extract, Alysicarpus ovalifolius, rodents.

Alysicarpus ovalifolius (Schumach. & Thonn.) J. Leonard is a legume species used as forage plant, which is originally native to Africa but today has a pantropical distribution. This species is probably expanding its distribution in the neotropics and therefore can be considered a potentially invasive species. In Brazil, the only species of Alysicarpus Neck. ex Desv. hitherto recorded was A. vaginalis (L.) DC., which is also non-native in the Americas. This study presents the fi rst account of the occurrence and distribution of A. ovalifolius in Brazil, including notes on its taxonomic status and potential invasiveness. Brazilian specimens of A. ovalifolius had been so far misidentifi ed as A. vaginalis. We also present here the fi rst records of the genus Alysicarpus in Santa Catarina state, southern Brazil, and provide an identifi cation key to the two species of Alysicarpus that occur in Brazil.