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: On two paradoxical side - effects of prednisolone in rats , ribosomal RNA biosyntheses , and a mechanism of action .
### Output Text:
On two paradoxical side - effects of <span class="chemical">prednisolone</span> in rats , ribosomal RNA biosyntheses , and a mechanism of action . 