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: Thus , aminoglycosides may act as nephrotoxicants at glomerular and / or tubular level inducing impairment of renal reabsorption and accumulation of proteins .
### Output Text:
Thus , <span class="chemical">aminoglycosides</span> may act as nephrotoxicants at glomerular and / or tubular level inducing impairment of renal reabsorption and accumulation of proteins . 