Anti-Nociceptive Activity of Fractionated Root Extract of Strophanthus hispidus DC (Apocynaceae)

Strophanthus hispidus DC belongs to the family of plants known as Apocynaceae, they are popularly known as poison arrow vine, brown strophanthus and hairy strophanthus in western part of Africa including Nigeria. This study investigated the anti-nociceptive property of ethyl acetate, n-butanol and aqueous fractions of the root extract of Strophanthus hispidus DC (Apocynaceae) in rodents of both sexes. The fractions, at a dose of 200 mg/kg each were given via oral route to the animals used in the various models-acetic acid-induced mouse writhing test, formalin- induced pain, Haffner's tail clip test, hot plate-induced pain and tail immersion test. In each of the models, the ethyl acetate fraction, n-butanol fraction and aqueous fraction of Strophanthus hispidus each possesses a significant (P<0.05, P<0.01, P<0.001) anti-nociceptive effect. The anti-nociceptive activity of the fractions was mediated through central and peripheral mechanism. The effect of the extract was comparable to that produced by peripheral analgesics the NSAIDs (aspirin) and centrally acting analgesic opioids (morphine) used as positive control in the various models employed. Phytochemical analysis of the fractions indicated the presence of flavonoids, cardiac glycosides, tannins, alkaloids and anthraquinones which also contributed to the anti-nociceptive activity of the extract.These findings showed the plant as a novel therapy for pain.