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: The study investigates if alpha - lipoic acid is neuroprotective against chemotherapy induced neurotoxicity , if mitochondrial damage plays a critical role in toxic neurodegenerative cascade , and if neuroprotective effects of alpha - lipoic acid depend on mitochondria protection .
### Output Text:
The study investigates if <span class="chemical">alpha - lipoic acid</span> is neuroprotective against chemotherapy induced neurotoxicity , if mitochondrial damage plays a critical role in toxic neurodegenerative cascade , and if neuroprotective effects of <span class="chemical">alpha - lipoic acid</span> depend on mitochondria protection . 