30431
MATERIALS AND METHODS : Anti - HRSV activities of hot water extracts of preparations of licorice , glycyrrhizin and 18 beta - glycyrrhetinic acid ( 18 beta - GA ) , the active constituents of licorice , were examined by plaque reduction assay in both human upper ( HEp - 2 ) and low ( A549 ) respiratory tract cell lines .
 glycyrrhizin, 18 beta - glycyrrhetinic acid, 18 beta - GA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 glycyrrhizin, 18 beta - glycyrrhetinic acid, 18 beta - GA