Neuropharmacological effects of Hibiscus sabdariffa aqueous extract

The neuropharmacological effects of the aqueous extract of Hibiscus sabdariffa (HS) calyx were studied in rodents. HS (100, 200 and 400 mg/kg, i.p.) caused a remarkable dose-dependent decrease in spontaneous motor activity in mice and increased the duration of pentobarbital (40 mg/kg, i.p.) induced sleep in rats. The extract (100-400 mg/kg, i.p.) significantly reduced the exploratory behaviour in mice. The extract significantly inhibited the intensity of apomorphine (1 mg/kg, s.c.) induced stereotypic behaviour and attenuated climbing in the mice dose-dependently. Similarly, chlorpromazine (3 mg/kg, i.p.) blocked apomorphine induced stereotype behaviour significantly. The intraperitoneal LD(50) of the extract was estimated to be greater than 5000 mg/kg. These results suggest that the aqueous extract of HS may contain psychoactive substances that are sedative in nature and which contribute to its use in traditional medicine as sedative.