Background: Leonotis nepetifolia
Linn (Lamiaceae) is used in traditional medicine for its calming (tranquilizing) effects. The aim of this
study was to determine whether there is any scientific justification for this use. To achieve this purpose, we investigated the behavioural
effects of the methanol extract of Leonotis nepetifolia
stem (37.5, 75 and 150 mg/kg) in mice.
Acute toxicity studies were carried out on the methanol stem extract of Leonotis nepetifolia
to determine the LD50
behavioural tests employed were diazepam-induced sleep onset and duration, hole board assay for exploratory activity, mouse beam walk
assay for motor coordination, and the staircase test for the detection of anxiolytic compounds. Preliminary phytochemical screening was
also carried out on the extract.
The intraperitoneal LD50
value was found to be 3.8 g/kg. The results showed that the extract significantly prolonged the duration
of diazepam-induced sleep at the highest dose (150 mg/kg). There was no observable effect on exploratory activity and motor
coordination at the doses tested (37.5, 75 and 150 mg/kg). The extract, however, at 150 mg/kg elicited a significant decrease in the
number of rearings in the staircase test, an effect also observed in the group of mice injected with an anxiolytic dose of diazepam. The
preliminary phytochemical screening revealed the presence of alkaloids, saponins, glycosides and triterpenoids.
The results obtained suggest that the crude methanol extract of Leonotis nepetifolia
stem possesses some biologically active
constituents with potential anxiolytic activity and thus may justify its traditional use as a tranquilizer.