1821
Morphinans have a storied history in medicinal chemistry as pain management drugs but have received attention as modulators of cholinergic signaling for the treatment of Alzheimer ' s Disease ( AD ) .
 Chemical: Morphinans
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Morphinans