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: Activity of CYP7A was decreased by EE in both intact and bile - diverted rats , whereas the activity of the CYP27 was not affected .
### Output Text:
Activity of CYP7A was decreased by <span class="chemical">EE</span> in both intact and bile - diverted rats , whereas the activity of the CYP27 was not affected . 