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: Daidzein activates choline acetyltransferase from MC - IXC cells and improves drug - induced amnesia .
### Output Text:
<span class="chemical">Daidzein</span> activates <span class="chemical">choline</span> acetyltransferase from MC - IXC cells and improves drug - induced amnesia . 