Evaluation of neuropharmacological effects of aqueous leaf extract of Albizia glaberrima (Leguminosae) in mice

Ethnopharmacological relevance: Albizia glaberrima is a shrub found in the deciduous forest and jungle of the coastal plain of West Africa. Preparations of the plant are used traditionally in the treatment of fever, pain and central nervous system disorders, including epilepsy. This study was conducted to investigate the neuropharmacological effects of the aqueous leaf extract of Albizia glaberrima in mice. Materials and methods: The hole-board, elevated plus-maze, thiopentone-induced sleep (anxiolytic/sedative-hypnotic), traction, climbing, inclined screen (muscle relaxant), strychnine-, picrotoxin- and pentylenetetrazole (PTZ)-induced convulsion (anticonvulsant) tests were employed in this study. Results: Albizia glaberrima extract at 200 mg/kg significantly increased the duration of head dips (p < 0.05) and number of open arms entry (p < 0.01) compared with control in the hole-board and elevated plus-maze tests, respectively. At 400 mg/kg, Albizia glaberrima extract significantly reduced the number of sectional crossings relative to control. The extract at 400 mg/kg significantly (p < 0.05) increased the duration of sleep compared with control in the thiopentone-induced hypnosis test. Albizia glaberrima extract at 200 mg/kg and diazepam (5 mg/kg) significantly (p < 0.05, 0.01) increased the post-treatment climbing time and reduced the latency to slide down in the climbing and inclined screen tests, respectively. The extract was not effective in the strychnine-induced seizure model, while in the picrotoxin test Albizia glaberrima extract at 100 mg/kg significantly (p < 0.05) reduced the duration of convulsion while reducing mortality at 400 mg/kg, as was the case with diazepam (2 mg/kg). The extract and diazepam significantly (p < 0.01, 0.001) increased onset and reduced duration of convulsion, with significant level of protection against convulsion and reduction in mortality in the PTZ-induced seizure model. Preliminary phytochemical screening of the extract revealed the presence of phenols > tannins > saponins > flavonoids. The extract was found to be relatively non-toxic when administered p.o. up to 5000 mg/kg and the LD50 was 398.11 mg/kg when administered i.p. Conclusions: The aqueous leaf extract of Albizia glaberrima possesses dose-dependent anxiolytic/muscle relaxant (low dose) and sedative-hypnotic/anticonvulsant (high dose) activities possibly mediated via enhancement of GABAergic inhibitory actions. (C) 2014 Published by Elsevier Ireland Ltd.