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: Antioxidant effects of bovine lactoferrin on dexamethasone - induced hypertension in rat .
### Output Text:
Antioxidant effects of bovine lactoferrin on <span class="chemical">dexamethasone</span> - induced hypertension in rat . 