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: In the animal study , Nrf2 was demonstrated to be crucial in ameliorating streptozotocin - induced renal damage .
### Output Text:
In the animal study , Nrf2 was demonstrated to be crucial in ameliorating <span class="chemical">streptozotocin</span> - induced renal damage . 