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: Effective compounds included norleucine , norvaline , glutamate , epsilon - aminocaproate , methionine , and leucine .
### Output Text:
Effective compounds included <span class="chemical">norleucine</span> , <span class="chemical">norvaline</span> , <span class="chemical">glutamate</span> , <span class="chemical">epsilon - aminocaproate</span> , <span class="chemical">methionine</span> , and <span class="chemical">leucine</span> . 