23697
In addition , structure - activity relationships and other important factors of the flavonoids binding to the active site of xanthine oxidase and cyclooxygenase - 2 were discussed , which is expected for further rational drug design .
 flavonoids, xanthine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 flavonoids, xanthine