Evaluation of the antidepressant activity of methanol extract and fractions of <i>Parquetina nigrescens</i> (Asclepidiaceae) leaves in mice

Abstract

Parquetina nigrescens is used in ethnomedicine for the management of pain, diabetes, wounds and central nervous system disorders. This study investigated the toxicity profile and antidepressant effects of methanol extract and fractions of leaves of P. nigrescens in murine models of depression. Phytochemical screening was conducted and the mean lethal dose was estimated. Antidepressant activity of the methanol extract, aqueous and chloroform fractions was evaluated using the forced swim and tail suspension tests at doses of 50, 100 and 200 mg/kg with imipramine (15 mg/kg) as the standard drug. Changes in body weights and organ weight ratio were also evaluated following treatment with P. nigrescens for 2 weeks. The mean lethal dose was estimated to be greater than 5 g/kg. Lower doses (50 and 100 mg/kg) of P. nigrescens significantly (p<0.05) reduced periods of immobility in both the forced swim and tail suspension tests. The aqueous fraction was more potent at ameliorating depression; no changes in body weights and organ weight ratios were recorded. The results obtained suggest that the leaf of P. nigrescens possesses antidepressant property which may account for its use in ethnomedicine.

Keywords:  Parquentina nigrescens, antidepressant, forced swim test, methanol extract, phytochemical tests