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 showed that aconitine resulted in myocardial injury and reduced NRVMs viability dose - dependently .
### Output Text:
The results showed that <span class="chemical">aconitine</span> resulted in myocardial injury and reduced NRVMs viability dose - dependently . 