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: In the propranolol - insulin group there was a significant fall in heart - rate in most subjects and an increase in diastolic pressure .
### Output Text:
In the <span class="chemical">propranolol</span> - insulin group there was a significant fall in heart - rate in most subjects and an increase in diastolic pressure . 