Anticonvulsant activity of Harpagophytum procumbens DC [Pedaliaceae] secondary root aqueous extract in mice.

Harpagophytum procumbens DC [family: Pedaliaceae] is widely used in South African traditional medicine for the treatment, management and/or control of a variety of human ailments. In the present study, we have examined the anticonvulsant activity of Harpagophytum procumbens secondary root aqueous extract (HPE, 50-800 mg/kg i.p.) against pentylenetetrazole (PTZ)-, picrotoxin (PCT)- and bicuculline (BCL)-induced seizures in mice. Phenobarbitone and diazepam were used as reference anticonvulsant drugs for comparison. Like the reference anticonvulsant agents used, H. procumbens secondary root aqueous extract (HPE, 100-800 mg/kg i.p.) significantly (P<0.05-0.001) delayed the onset of, and antagonized, pentylenetetrazole (PTZ)-induced seizures. The plant's extract (HPE, 100-800 mg/kg i.p.) also profoundly antagonized picrotoxin (PCT)-induced seizures, but only partially and weakly antagonized bicuculline (BCL)-induced seizures. Although the data obtained in the present study do not provide conclusive evidence, it would appear that H. procumbens secondary root aqueous extract (HPE) produces its anticonvulsant activity by enhancing GABAergic neurotransmission and/or facilitating GABAergic action in the brain. In general, the average onset of convulsion was delayed, while the average duration of convulsion was markedly reduced. The plant's extract also depressed the central nervous system (CNS). It is, therefore, thought that the anticonvulsant property of the herb may be linked, at least in part, to its ability to depress the central nervous system. However, the results of this experimental animal study indicate that H. procumbens secondary root aqueous extract possesses anticonvulsant activity, and thus lend pharmacological support to the suggested folkloric, ethnomedical uses of the plant's extract in the treatment, management and/or control of epilepsy and childhood convulsions in some rural communities of South Africa.