Antidepressant effects of the hydro-alcoholic extract and fractions of Anchomanes difformis (Blume) Engler rhizome (family Araceae) in mice

In ethno-medicinal practice in the South-western part of Nigeria, the rhizome of Anchomanes difformis is claimed to be effective in the management of mental illness. This study determined the antidepressant effects of hydro-alcoholic extract and fractions of Anchomanes difformis rhizome and the likely mechanisms of action of the extract and the most active fraction in mice. The extract was partitioned into n-hexane, ethylacetate, butanol and distilled water to obtain n-hexane, ethylacetate, butanol and residual aqueous fractions, respectively. The extract and fractions were administered to mice of both sexes (18 to 25 g) at 60, 125, 250, 500, and 1000 mg/kg, orally. Tail suspension and forced swimming anti-depressant animal models were used. The likely mechanism of anti-depressant action was assessed using yohimbine and cyproheptadine. The data were analyzed using one-way ANOVA followed by Student-Newman-Keul’s post hoc test with the level of significance taken as p<0.05. The extract and ethylacetate fraction at 60 to 250 mg/kg significantly (p<0.05) reduced the period of immobility in both the tail suspension and forced swimming tests without significantly impairing the locomotor activity, suggesting an anti-depressant effect. This effect was reversed by yohimbine (1 mg/kg, i.p.), an α2-adrenergic receptor antagonist, yohimbine and also by cyproheptadine (0.5 mg/kg, i.p.), a serotonergic receptor antagonist. The study concluded that the extract and ethylacetate fraction of A. difformis rhizome possessed an anti-depressant effect in mice which was probably mediated through α2-adrenergic and serotonergic pathways.