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 cardioprotective effect of the ethanol extract of Picrorrhiza kurroa rhizomes and roots ( PK ) on isoproterenol - induced myocardial infarction in rats with respect to lipid metabolism in serum and heart tissue has been investigated .
### Output Text:
The cardioprotective effect of the <span class="chemical">ethanol</span> extract of Picrorrhiza kurroa rhizomes and roots ( PK ) on <span class="chemical">isoproterenol</span> - induced myocardial infarction in rats with respect to lipid metabolism in serum and heart tissue has been investigated . 