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: Curcumin prevents maleate - induced nephrotoxicity : relation to hemodynamic alterations , oxidative stress , mitochondrial oxygen consumption and activity of respiratory complex I .
### Output Text:
<span class="chemical">Curcumin</span> prevents <span class="chemical">maleate</span> - induced nephrotoxicity : relation to hemodynamic alterations , oxidative stress , mitochondrial <span class="chemical">oxygen</span> consumption and activity of respiratory complex I . 