Hypnotic Effect of Portulaca oleracea on Pentobarbital-Induced Sleep in Mice.

OBJECTIVE: In Iranian Traditional Medicine, the herbs with cold and wet temperament can help to improve insomnia. Portulaca oleracea has a cold and wet temperament, so the present study was carried out to investigate the sleep-prolonging effect of Portulaca oleracea. METHODS: This work was an experimental study on mice which were randomly divided into these groups: saline (control); Diazepam: positive control); hydro-alcoholic extract of Portulaca oleracea (12.5, 25, 50, 75 and 100 mg/kg) by Soxhlet apparatus and maceration; in the effective (dose25 mg/kg), different fractions of extract were tested. Ethyl acetate fraction (EAF:); N hexane fraction (n-HF); water fraction (WF). All the test compounds were injected intraperitoneally (IP) 30 minutes before pentobarbital administration (30 mg/kg). Duration and latency of pentobarbital-induced sleep were recorded. Also, LD50 of Portulaca oleracea extract was determined and the possible neurotoxicity of the extract was tested on neural PC12 cells. Besides, 30 min after administration of hydroalcoholic extract (HAE) motor coordination (rota-rod test) was assessed. RESULTS: HAE increased the duration of pentobarbital-induced sleep at doses of 25, 50, 75 and 100 mg/kg. The hypnotic effect of HAE was comparable to that induced by diazepam. Similarly, WF, EAF, and NHF at 25 mg/kg could increase sleep duration. The sleep latency was decreased by HAE and NHF but not by WF and EAF. The LD50 value for HAE was found to be 4.8 g/Kg. HAE and its fractions did not show neurotoxic effect in cultured PC12-cell line, also HAE did not affect the animals performance on the rotarod test. CONCLUSION: The present data demonstrated that Portulaca oleracea potentiates sleeping behaviors. The main components responsible for the hypnotic effects of this plant is most likely a non-polar agents which is found in NHF. Isolation of the active constituents may yield a novel sedative drug.