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: Herein , we investigate whether doxorubicin - associated chronic cardiac toxicity can be ameliorated with the antioxidant hydroxytyrosol in rats with breast cancer .
### Output Text:
Herein , we investigate whether <span class="chemical">doxorubicin</span> - associated chronic cardiac toxicity can be ameliorated with the antioxidant <span class="chemical">hydroxytyrosol</span> in rats with breast cancer . 