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: Quinine , like quinidine , is a chincona alkaloid that has anti - arrhythmic property , although it also pro - arrhythmic that can cause various arrhythmias , including severe arrhythmia such as multiple PVC .
### Output Text:
<span class="chemical">Quinine</span> , like <span class="chemical">quinidine</span> , is a chincona alkaloid that has anti - arrhythmic property , although it also pro - arrhythmic that can cause various arrhythmias , including severe arrhythmia such as multiple PVC . 