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 renal injury was probably aggravated by the concomitant intake of a non - steroidal anti - inflammatory drug , diclofenac .
### Output Text:
The renal injury was probably aggravated by the concomitant intake of a non - steroidal anti - inflammatory drug , <span class="chemical">diclofenac</span> . 