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: The current study dealt with the protective role of mangiferin , a polyphenol from Mangifera indica Linn .
### Output Text:
The current study dealt with the protective role of <span class="chemical">mangiferin</span> , a <span class="chemical">polyphenol</span> from Mangifera indica Linn . 