Abstract: The anticonvulsant activity of Zanthoxylum capense
(Thunb.) Harv. (Rutaceae) was investigated by studying the effects of the leaf
methanol and aqueous extracts on seizures induced by pentylenetetrazole, bicuculline,
picrotoxin, N-methyl-DL-aspartic acid and strychnine in mice. Both methanol
and aqueous extracts of Z. capense significantly antagonized (p<0.05-0.005)
seizures induced by pentylenetrazole (PTZ), picrotoxin and strychnine. Methanol
extract of Z. capense significantly antagonized (p<0.05) bicuculline-induced
seizures while the aqueous extract significantly delayed (p<0.001) the onset
of the seizures. Both methanol and aqueous extracts of the plant species significantly
delayed (p<0.05-0.005) the onset of N-methyl-DL-aspartic acid (NMDLA)-induced
seizures. Phenobarbitone and diazepam significantly antagonized (p<0.001)
seizures induced by PTZ, bicuculline and picrotoxin but did not alter NMDLA-induced
seizures. Phenobarbitone significantly attenuated (p<0.01) strychnine-induced
seizures. Phenytoin or dimethylsulfoxide did not alter the seizures induced
either by PTZ, bicuculline, picrotoxin, NMDLA or strychnine to any extent. The
LD50 value obtained following oral administration of both the leaf
aqueous and methanol extracts of Z. capense was above 3200 mg kg-1
and that obtained after intraperitoneal administration was 283.6 mg kg-1.
The phytochemical analysis of the plant species revealed the presence of alkaloids,
triterpene steroids, reducing sugars, saponins, tannins and quinones. The data
obtained indicate that the leaf methanol and aqueous extracts of Z. capense
have anticonvulsant activity which may probably involve both GABAergic, glutaminergic
and glycinergic mechanisms. The relatively high LD50 value obtained
following oral administration of the plant extract shows that it is non-toxic
and /or safe in mice. |