Nootropic Activity of Calyces of Hibiscus sabdariffa     Linn

Nootropic acitivity of calyces of Hibiscus sabdariffa Linn. was studied in mice. Elevated plus maze and passive avoidance paradigm were employed to evaluate learning and memory parameters. Scopolamine (0.4 mg/kg, i.p.) was used to induce amnesia in mice. The aqueous extracts of calyces of Hibiscus sabdariffa (HS-100 and 200 mg/kg, p.o.) significantly attenuated amnestic deficits induced by scopolamine (0.4 mg/kg, i.p.) and natural aging. HS (100 and 200 mg/kg) decreased the transfer latencies and increased step down latencies significantly in the aged mice and scopolamine induced amnesic mice as compared with Piracetam (200 mg/kg, i.p.). To delineate the possible mechanism through which H. sabdariffa elicits the anti-amnesic effects, we studied its influence on central cholinergic activity by estimating the whole brain acetylcholinesterase activity. H. sabdariffa significantly decreased acetyl cholinesterase activity in mice. The results indicate that, the aqueous extract of calyces of H. sabdariffa might prove to be a useful memory restorative agent in the treatment of dementia seen in elderly. The underlying mechanism of action can be attributed to its anti acetylcholinesterase property.