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: Several structurally related metabolites of progesterone ( 3 alpha - hydroxy pregnane - 20 - ones ) and deoxycorticosterone ( 3 alpha - hydroxy pregnane - 21 - diol - 20 - ones ) and their 3 beta - epimers were evaluated for protective activity against pilocarpine - , kainic acid - and N - methyl - D - aspartate ( NMDA ) - induced seizures in mice .
### Output Text:
Several structurally related metabolites of <span class="chemical">progesterone</span> ( <span class="chemical">3 alpha - hydroxy pregnane - 20 - ones</span> ) and <span class="chemical">deoxycorticosterone</span> ( <span class="chemical">3 alpha - hydroxy pregnane - 21 - diol - 20 - ones</span> ) and their 3 beta - epimers were evaluated for protective activity against <span class="chemical">pilocarpine</span> - , <span class="chemical">kainic acid</span> - and <span class="chemical">N - methyl - D - aspartate</span> ( <span class="chemical">NMDA</span> ) - induced seizures in mice . 