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: Numerous anecdotal reports suggest that products containing quinine may produce neurological complications , including confusion , altered mental status , seizures , and coma , particularly in older women .
### Output Text:
Numerous anecdotal reports suggest that products containing <span class="chemical">quinine</span> may produce neurological complications , including confusion , altered mental status , seizures , and coma , particularly in older women . 