Antipsychotic property of solvent-partitioned fractions of Lonchocarpus cyanescens leaf extract in mice.

BACKGROUND

This study was carried out to evaluate the antipsychotic property of solvent-partitioned fractions of the leaf extract of Lonchocarpus cyanescens (LC), a reputable medicinal plant used in folk medicine for the treatment of mental illnesses in Nigeria.

METHODS

The n-hexane fraction, ethyl acetate fraction (EAF), and aqueous ethanol fraction (AEF) of LC were tested for antipsychotic property based on the antagonism of stereotypy induced by apomorphine (APO). Antagonism of hyperactivity and lethality in aggregated mice induced by amphetamine (AMPH) were further employed for screening the antipsychotic effect of the fractions. EAF was tested for catalepsy utilising the horizontal plane paradigm. Thin-layer chromatography (TLC) was used to screen EAF for the presence of secondary metabolites.

RESULTS

AEF (100-400 mg/kg) significantly (p<0.05) suppressed stereotypy induced by APO (2 mg/kg, intraperitoneal [IP]) in comparison with control, suggesting antipsychotic activity. However, EAF (200 mg/kg, IP) was most potent in inhibiting the stereotypic effect of APO. EAF was also the most active in antagonising AMPH-induced hyperactivity and in protecting against death caused by AMPH in grouped mice. However, in contrast to haloperidol, EAF did not produce cataleptic behaviour in the horizontal plane paradigm. The TLC analysis revealed that EAF contains several compounds, with some of them having Rf values similar to that of haloperidol, which suggests the presence of active substances with the same chemical structural identity.

CONCLUSIONS

These findings suggest that EAF contains the major active constituent(s) mediating the antipsychotic property of LC and further support its use for the management of psychosis in traditional medicine.