ABSTRACT

Medicinal plants are plants used for therapeutic purposes. Andrographis paniculata Nees (Acanthaceae) commonly called “king of bitters” has been used traditionally for the treatment of a wide array of ailments such as asthma, hyperglycemia, bacterial infections, inflammation and common cold. The aim of this study was to evaluate the antipsychotic and anxiolytic property of the methanol leaf extract of Andrographis paniculata (MEAP).

All the experiments were conducted using male and female mice. The oral median lethal dose (LD₅₀) was estimated using the Locke method. The antipsychotic property was evaluated at specific time points (T₃₀ to T₁₂₀) post treatment using the amphetamine induced stereotype behavior model and the ketamine induced hyperactivity model with haloperidol as the standard in each case. The anxiolytic property was evaluated using the elevated plus maze test with diazepam as the standard. The sleep enhancing property was evaluated using the phenobarbital induced sleep time test with diazepam as the standard.

The oral LD₅₀ of MEAP was estimated to be greater than 5000 mg/kg. MEAP significantly reduced amphetamine induced stereotype behavior with 400 mg/kg (P<0.01) at T₃₀; 200 mg/kg (P<0.01), and 400 mg/kg (P<0.0001) at T₆₀; 200 mg/kg (P<0.05) and 400 mg/kg (P<0.01) at T₉₀; and 100 mg/kg (P<0,01), 200 mg/kg (P<0.05) and 400 mg/kg (P<0.0001) at T₁₂₀. In the ketamine model, there was a significant reduction in periods of immobility at 200 mg/kg (P<0.05) and 400 mg/kg (P<0.01) at T₁₂₀. In the elevated plus maze test, there was no significant difference between the control and those that received MEAP in the frequency of entry and duration of time spent in the open arms. The extract did not significantly decrease onset or increase duration of phenobarbital induced sleeping time in mice. It is concluded that MEAP may be safe on oral acute administration and possesses antipsychotic property but lacks anxiolytic and sleep enhancing properties.