9859
For this project , quercetin , catechin , ascorbic acid , caffeic acid , chlorogenic acid and acetylcysteine were screened as antioxidant standards with DPPH ( . ) assay to define the EC ( 50 ) parameters .
 quercetin, catechin, ascorbic acid, caffeic acid, chlorogenic acid, acetylcysteine, DPPH ( . )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 quercetin, catechin, ascorbic acid, caffeic acid, chlorogenic acid, acetylcysteine, DPPH ( . )