5348
Purine and pyrimidine nucleotides have been viewed as primordial precursors in the evolution of all forms of intercellular communication , and they are now regarded as fundamental extracellular signalling molecules .
 Chemical: Purine; Chemical: pyrimidine; Chemical: nucleotides
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: Purine, pyrimidine, nucleotides 
Answer:
 Chemical: Purine; Chemical: pyrimidine; Chemical: nucleotides