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: Effect of captopril on pre - existing and aminonucleoside - induced proteinuria in spontaneously hypertensive rats .
### Output Text:
Effect of <span class="chemical">captopril</span> on pre - existing and <span class="chemical">aminonucleoside</span> - induced proteinuria in spontaneously hypertensive rats . 