A pharmaceutical composition comprising a herbal extract, comprising a mixture of saponins prepared from the pericarp of Sapindus trifoliatus, with binding affinities for the receptor sites viz. GABA-A agonist site, Glutamate-AMPA site, Glutamate-Kainate site, Glutamate-NMDA agonistic site, Glutamate-NMDA glycine (strychnine insensitive) site and Sodium channel (site 2), having major mediatory role in anticonvulsant activity. A process for preparation of the herbal extract; isolation of six pure compounds from the mixture of saponins in the aqueous extract; and a pharmaceutical composition comprising the said extract in combination with pharmaceutically acceptable additives. A method of prophylactic treatment of migraine through anticonvulsant activity of the composition by its administration through intranasal route.