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: T . chebula extract pretreatment was found to ameliorate the effect of isoproterenol on lipid peroxide formation and retained the activities of the diagnostic marker enzymes .
### Output Text:
<span class="chemical">T . chebula extract</span> pretreatment was found to ameliorate the effect of <span class="chemical">isoproterenol</span> on lipid <span class="chemical">peroxide</span> formation and retained the activities of the diagnostic marker enzymes . 