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: Fenoldopam mesylate is a specific DA1 receptor agonist that lowers blood pressure by vasodilatation .
### Output Text:
<span class="chemical">Fenoldopam mesylate</span> is a specific DA1 receptor agonist that lowers blood pressure by vasodilatation . 