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 reduction effect of D - glucarates against nephrotoxicity of basic antibiotics was discussed .
### Output Text:
The reduction effect of <span class="chemical">D - glucarates</span> against nephrotoxicity of basic antibiotics was discussed . 