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: Oral administration of betaine ( 200 and 400 mg / kg ) significantly reduced the level of cardiac marker enzyme in the serum and prevented left ventricular remodeling .
### Output Text:
Oral administration of <span class="chemical">betaine</span> ( 200 and 400 mg / kg ) significantly reduced the level of cardiac marker enzyme in the serum and prevented left ventricular remodeling . 