Anticonvulsant activity of Carissa edulis (Vahl) (Apocynaceae) root bark extract

AIM OF THE STUDY: To investigate the anticonvulsant activity of root bark extract of Carissa edulis. MATERIALS AND METHODS: The median lethal dose (LD(50)) of Carissa edulis extract was determined using Lork's method (1983). The anticonvulsant activity of the extract was assessed in pentylenetetrazole (PTZ)-induced convulsion in mice and maximal electroshock test (MEST) in chicks, with benzodiazepine and phenytoin as standard drugs, respectively. While mechanistic studies were conducted using both flumazenil, a GABA(A)-benzodiazepine receptor complex site antagonist and naloxone a non-specific opioid receptor antagonist. RESULTS: The median lethal dose (LD(50)) of Carissa edulis was 282.8mg/kg and over 5000mg/kg following intraperitoneal and oral administration, respectively. Carissa edulis produced 40% and 20% protection against convulsion at 5 and 20mg/kg, respectively, compared with 100% protection with benzodiazepine. The mean onset and percentage protection against convulsion in Carissa edulis extract-treated mice were reduced by flumazenil and naloxone. Carissa edulis exhibited dose-dependent inhibition of the convulsion induced by MEST with 20mg/kg providing 90% protection while phenytoin (20mg/kg) produced 100% protection. CONCLUSION: These results suggest that Carissa edulis possesses biologically active constituent(s) that have anticonvulsant activity which supports the ethnomedicinal claims of the use of the plant in the management of epilepsy.