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: This suggests that alpha - TC and DFO ameliorate the MA - induced neuronal damage by decreasing the level of oxidative stress .
### Output Text:
This suggests that <span class="chemical">alpha - TC</span> and <span class="chemical">DFO</span> ameliorate the <span class="chemical">MA</span> - induced neuronal damage by decreasing the level of oxidative stress . 