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: Our results suggest a role for levodopa in the oral phase of deglutition and confirm that dysphagia is not a good predictor of deglutition alterations in PD .
### Output Text:
Our results suggest a role for <span class="chemical">levodopa</span> in the oral phase of deglutition and confirm that dysphagia is not a good predictor of deglutition alterations in PD . 