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: We report a 23 - year - old woman who developed acute renal failure following prolonged use of a proprietary Chinese herbal slimming pill that contained anthraquinone derivatives , extracted from Rhizoma Rhei ( rhubarb ) .
### Output Text:
We report a 23 - year - old woman who developed acute renal failure following prolonged use of a proprietary <span class="chemical">Chinese herbal</span> slimming pill that contained <span class="chemical">anthraquinone</span> derivatives , extracted from Rhizoma Rhei ( rhubarb ) . 