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 : Adenosine produced no effect on pain report to acute noxious thermal or chemical stimulation but reduced mechanical hyperalgesia and allodynia from intradermal capsaicin injection for at least 24 h .
### Output Text:
RESULTS : <span class="chemical">Adenosine</span> produced no effect on pain report to acute noxious thermal or chemical stimulation but reduced mechanical hyperalgesia and allodynia from intradermal <span class="chemical">capsaicin</span> injection for at least 24 h . 