An Anticonvulsant Diterpene Lactone Isolated From the Leaves of Leonotis leonorus (L) R. BR

Chemical, physical and pharmacological methods were used to isolate, identify and evaluate an anticonvulsant diterpene lactone obtained from the leaves of Leonotis leonorus. Tonic seizures were chemically induced in mice using pentylenetetrazole (PTZ) at a dose of 95 mg/kg intraperitoneally. Extracts of the plant material obtained with hexane and methanol, and fractions obtained from the methanol extract were tested for anticonvulsant activities. The crude methanol extract at a dose of 100-400 mg/kg ip significantly delayed the onset of tonic seizures induced by pentylenetetrazole with 100 mg/kg ip of the extract protecting 50 % of the mice against seizures. Additionally, compound II (unknown) from the methanol extract at 200 mg/kg ip and 400 mg/kg ip protected 75 % and 87.5 % of mice respectively against the seizures while 100-400 mg/kg ip of 20-Acetoxy-9α,13α-epoxylabda-14-en-6β(19)-lactone (compound I) significantly delayed the onset of pentratetrazole-induced seizures and protected 50 % of the mice against seizures at 400 mg/kg. The active diterpene lactone was characterised using spectroscopic methods.. Keywords : Anticonvulsant activity, isolation, diterpene lactone, Leonotis leonorus , mice The East and Central African Journal of Pharmaceutical Sciences Vol. 8 (3) 2005: pp 54-61