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 wish to draw attention to the possibility of adverse reactions to ACE inhibitors after long - term use and in patients with pre - existing angio - oedema .
### Output Text:
We wish to draw attention to the possibility of adverse reactions to <span class="chemical">ACE inhibitors</span> after long - term use and in patients with pre - existing angio - oedema . 