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: Despite reports to the contrary , it is suggested that sulphasalazine may be teratogenic .
### Output Text:
Despite reports to the contrary , it is suggested that <span class="chemical">sulphasalazine</span> may be teratogenic . 