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: The results of our study suggest that salvianolic acid A possessing antioxidant activity has a significant protective effect against isoproterenol - induced myocardial infarction .
### Output Text:
The results of our study suggest that <span class="chemical">salvianolic acid A</span> possessing antioxidant activity has a significant protective effect against <span class="chemical">isoproterenol</span> - induced myocardial infarction . 