27211
Trapping of a Cross - Link Formed by a Major Purine Adduct of a Metabolite of the Carcinogen N - Nitrosomorpholine by Inorganic and Biological Reductants .
 Purine, N - Nitrosomorpholine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Purine, N - Nitrosomorpholine