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: Addition of oral nicorandil reduced his symptoms and maintained stable angina status .
### Output Text:
Addition of oral <span class="chemical">nicorandil</span> reduced his symptoms and maintained stable angina status . 