Anticonvulsant activity of thymoquinone and its structural analogues

It has been widely reported that the crude oil of Nigella sativa L., Ranunculaceae, seeds and its major chemical component thymoquinone present anticonvulsant activity. These facts led us to verify the pharmacological potential of five structurally related para-benzoquinones on the pentylenotetrazol-induced seizures model, and establish the structural characteristics that influence the anticonvulsant activity of thymoquinone. The unsubstituted para-benzoquinone was the compound that exhibited the highest potency, while 2-methyl-p-benzoquinone was inactive. It was found that the presence of alkyl groups attached to the ring influence the pharmacological activity of the para-benzoquinones. In addition, the number, position, and size of these groups change the anticonvulsant potency of the compounds.

Anticonvulsant activity of the linalool enantiomers and racemate: investigation of chiral influence.

The anticonvulsant activity of the racemate and enantiomers of linalool have been evaluated. Pretreatment of the mice with (S)-(+)-, (R)-(-)- and rac-linalool increased the latency of convulsions significantly in the PTZ model. Only rac-linalool had an effect at the dose of 200 mg/kg. The enantiomers and their racemic mixture were effective in inhibiting the convulsant effect of PTZ at the dose of 300 mg/kg. The linalools presented pharmacological activity close to that of diazepam. In the PIC seizure model, (R)-(-)-linalool and rac-linalool presented activity at the dose of 200 mg/kg, but the rac-linalool was more potent than (R)-(-)-linalool; (S)-(+)-linalool had no effect at this dose. On the other hand, at the dose of 300 mg/kg this enantiomer was effective, but less potent than (R)-(-)-linalool and rac-linalool. In the MES model, linalools decreased the convulsion time of the mice in the doses of 200 and 300 mg/kg. rac-Linalool presented maximum effect at 300 mg/kg. Surprisingly, it increased significantly the convulsion time at a dose of 100 mg/kg. Using the parameter of tonic hind convulsions, only (R)-(-)-linalool produced protection from tonic extension at the dose of 200 mg/kg. When the (+)- and (-)-enantiomers, and rac-linalool were administered at the dose of 300 mg/kg they were also effective in preventing tonic convulsions induced by transcorneal electroshock in the animals. The (+)- and (-)-forms were equipotent and the rac-linalool was more effective than phenytoin. We have demonstrated that the two enantiomers have similar qualitative anticonvulsant activity, but show different potencies.