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: Anticonvulsant effect of eslicarbazepine acetate ( BIA 2 - 093 ) on seizures induced by microperfusion of picrotoxin in the hippocampus of freely moving rats .
### Output Text:
Anticonvulsant effect of <span class="chemical">eslicarbazepine acetate</span> ( <span class="chemical">BIA 2 - 093</span> ) on seizures induced by microperfusion of <span class="chemical">picrotoxin</span> in the hippocampus of freely moving rats . 