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As a result of this study , microgrewiapine A ( 1 ) was found to be a selective cytotoxic agent for colon cancer cells over normal colon cells and to exhibit nicotinic receptor antagonistic activity for both the h alpha 3 beta 4 and h alpha 4 beta 2 receptor subtypes .
 microgrewiapine A
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 microgrewiapine A