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: Alpha - lipoic acid prevents mitochondrial damage and neurotoxicity in experimental chemotherapy neuropathy .
### Output Text:
<span class="chemical">Alpha - lipoic acid</span> prevents mitochondrial damage and neurotoxicity in experimental chemotherapy neuropathy . 