Evaluation of anticonvulsant effect of aqueous and methanolic extracts of seven Inula species

Abstract

In Iranian traditional medicine, plants belonging to Inula genus have been used for the treatment of seizure. We decided to investigate the anticonvulsant activity of seven species from this genus to find an effective remedy for seizure with less adverse effects compared to available medicines. Aqueous and methanolic extracts of Inula britannica, Inula helenium, Inula viscidula, Inula oculus-christi, Inula aucheriana, Inula thapsoides and Inula salicina were prepared and their antiepileptic activity was investigated by maximal electroshock and pentylentetrazole tests. Diazepam was used as positive control in both tests. Two extracts with the best anticonvulsant activities were selected and their sedative and hypnotic effects were evaluated using open field and righting reflex tests respectively. The effects of both extracts on memory and motor coordination were also assessed by step-through passive avoidance and rotarod tests respectively. Aqueous extract of Inula britannica and Inula viscidula showed the best activity in MES model and their ED50 was 19.5(7.9~48.5)mg/kg and 12.7(10.0~16.3)mg/kg respectively. None of the extracts showed noticeable anticonvulsant effects in the PTZ model. The active extracts showed sedative-hypnotic effects in righting reflex and open field tests. Both extracts did not affect the memory and motor coordination in the experimental model. The anticonvulsant and sedative activities of the extracts were antagonized by flumazenil, indicating that benzodiazepine receptors are probably involved in the effects. Finally, Inula britannica and Inula viscidula are good candidates for further phytochemical and mechanistic studies in order to find anticonvulsant and sedative-hypnotic agents with less adverse effect on memory and motor coordination.