AN EVALUATION OF THE ANALGESIC ACTION OF AQUEOUS LEAVES EXTRACT OF HYBANTHUS ENNEASPERMUS LINN. F. MUELL [VIOLACEAE] IN RODENTS

Abstract

Hybanthus enneaspermus is a tropical and subtropical shrub used to manage conditions involving inflammation and pain. This study was carried out to evaluate the analgesic activity of aqueous leaves extract of H. enneaspermus (ALHE). The analgesic activity of ALHE (50, 100 and 200 mg/kg) was investigated using acetic acid- and acetylcholine-induced mouse writhing tests, formalin-induced pain and tail clip tests in mice. Naloxone, glibenclamide or pilocarpine was administered to some animals 30 minutes before ALHE prior to induction of pain.  Possible contribution of central nervous system (CNS) activity of the extract to its analgesic action was also evaluated using open field and hexobarbitone-induced sleep tests. The extract (50-200 mg/kg) significantly inhibited writhing in the acetic acid- and acetylcholine-induced mouse writhing tests. It was most effective at 100 mg/kg, producing 97.6% and 96.5% inhibition in both tests respectively. Naloxone, glibenclamide and pilocarpine significantly (p<0.001) altered this analgesic effect of the extract. The extract also significantly (p<0.001) increased pain threshold in tail clip test and significantly reduced reaction time in both phases of the formalin-induced pain test. The extract significantly reduced locomotive and exploratory activities of mice in the open field test but did not produce any significant effect in the hexobarbitone-induced sleep test in mice. These findings show that the aqueous leaves extract of Hybanthus enneaspermus possesses analgesic activity, which is mediated by mechanisms likened to those of opioid receptor antagonists, muscarinic receptor antagonists, and K⁺ channels opening