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: This lack of effects may stem from the low contribution of de - novo synthesis to cellular inositol supply or to the inhibition of the de - novo synthesis by lithium itself .
### Output Text:
This lack of effects may stem from the low contribution of de - novo synthesis to cellular <span class="chemical">inositol</span> supply or to the inhibition of the de - novo synthesis by <span class="chemical">lithium</span> itself . 