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: Plasma malondialdehyde , which was present in minimal amount at zero time ( 0 . 058 mumol / liter plasma ; SD 0 . 015 ) , increased after 5 min of ischemia , resulting in a fivefold increase after 30 min of carotid occlusion ( 0 . 298 mumol / liter plasma ; SD 0 . 078 ) .
### Output Text:
Plasma <span class="chemical">malondialdehyde</span> , which was present in minimal amount at zero time ( 0 . 058 mumol / liter plasma ; SD 0 . 015 ) , increased after 5 min of ischemia , resulting in a fivefold increase after 30 min of carotid occlusion ( 0 . 298 mumol / liter plasma ; SD 0 . 078 ) . 