In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The present study aimed to evaluate the GFC effects at doses of 25 , 50 or 75 mg / kg on seizure parameters to determine their anticonvulsant activity and its effects on amino acid ( r - aminobutyric acid ( GABA ) , glutamine , aspartate and glutathione ) levels as well as on acetylcholinesterase ( AChE ) activity in mice hippocampus after seizures .
### Output Text:
The present study aimed to evaluate the <span class="chemical">GFC</span> effects at doses of 25 , 50 or 75 mg / kg on seizure parameters to determine their anticonvulsant activity and its effects on <span class="chemical">amino acid</span> ( <span class="chemical">r - aminobutyric acid</span> ( <span class="chemical">GABA</span> ) , <span class="chemical">glutamine</span> , <span class="chemical">aspartate</span> and <span class="chemical">glutathione</span> ) levels as well as on acetylcholinesterase ( AChE ) activity in mice hippocampus after seizures . 