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: ZnSO ( 4 ) pretreatment counteracted BCNU - induced inhibition of GR and depletion of GSH and resulted in significant reduction in the levels of MDA and TNFalpha as well as the activity of caspase - 3 .
### Output Text:
<span class="chemical">ZnSO ( 4 )</span> pretreatment counteracted <span class="chemical">BCNU</span> - induced inhibition of GR and depletion of <span class="chemical">GSH</span> and resulted in significant reduction in the levels of <span class="chemical">MDA</span> and TNFalpha as well as the activity of caspase - 3 . 