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: Effect of alpha - tocopherol and deferoxamine on methamphetamine - induced neurotoxicity .
### Output Text:
Effect of <span class="chemical">alpha - tocopherol</span> and <span class="chemical">deferoxamine</span> on <span class="chemical">methamphetamine</span> - induced neurotoxicity . 