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 exerts neuroprotective effects against chemotherapy induced neurotoxicity in sensory neurons : it rescues the mitochondrial toxicity and induces the expression of frataxin , an essential mitochondrial protein with anti - oxidant and chaperone properties .
### Output Text:
<span class="chemical">Alpha - lipoic acid</span> exerts neuroprotective effects against chemotherapy induced neurotoxicity in sensory neurons : it rescues the mitochondrial toxicity and induces the expression of frataxin , an essential mitochondrial protein with anti - oxidant and chaperone properties . 