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: Neither progesterone nor estradiol effects on bupivacaine arrhythmogenicity were potentiated by epinephrine .
### Output Text:
Neither <span class="chemical">progesterone</span> nor <span class="chemical">estradiol</span> effects on <span class="chemical">bupivacaine</span> arrhythmogenicity were potentiated by <span class="chemical">epinephrine</span> . 