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: RESULTS : From a database of 452 patients receiving Botox , 352 patients had been diagnosed with ADSD .
### Output Text:
RESULTS : From a database of 452 patients receiving <span class="chemical">Botox</span> , 352 patients had been diagnosed with ADSD . 