Antipsychotic property of aqueous and ethanolic extracts of Lonchocarpus cyanescens (Schumach and Thonn.) Benth. (Fabaceae) in rodents

Lonchocarpus cyanescens (LC) is a medicinal plant commonly used in combination with other recipes in the treatment of psychotic disorders in traditional medicine. This study was designed to examine whether the aqueous and ethanolic extracts of LC possess antipsychotic property in rats. The antipsychotic effects of the extracts were assessed using the amphetamine animal model of psychosis in rats. The effect of the extracts on spontaneous motor activity was also studied in the open field test in mice. The extrapyramidal side effect of catalepsy was tested based on the ability of the extracts to alter the duration of akinesia in mice placed on a vertical wrapped string. Aqueous and ethanolic extracts of LC (25–400 mg/kg, i.p.) significantly (p < 0.05) suppressed stereotyped behaviour induced by amphetamine (10.0 mg/kg, i.p.) in rats, which suggest antipsychotic activity. The extracts (25–400 mg/kg, i.p.) further produced a significant (p < 0.05) reduction in spontaneous motor activity of the animals in the open field test. However, in contrast to chlorpromazine, a typical antipsychotic, the extracts did not induce cataleptic behaviour in the animals. Preliminary phytochemical screening showed the presence of alkaloids, anthraquinones, cardiac glycosides, cyanogenetic glycosides, flavonoids, saponins, steroids and tannins in the leaves of LC. The presence of these secondary metabolites was confirmed by thin-layer chromatography. Taken together, these findings suggest that the extracts possess phytochemically active constituents with antipsychotic property. Thus, this investigation provides evidence that may justify the ethnomedicinal applications of Lonchocarpus cyanescens as the major constituent of the recipe used for the management of psychosis in Nigeria.