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: High fat diet - fed obese rats are highly sensitive to doxorubicin - induced cardiotoxicity .
### Output Text:
High <span class="chemical">fat</span> diet - fed obese rats are highly sensitive to <span class="chemical">doxorubicin</span> - induced cardiotoxicity . 