13182
A novel homoflavanol derivative ( 1 ) with an unprecedented skeleton , as well as two known flavonoids kaempferol ( 2 ) and quercetin ( 3 ) , was isolated from the plant Pteridium aquilinum ( L . ) Kuhn , and the structure and relative stereochemistry of the new compound ( 1 ) were elucidated on the basis of spectroscopic data .
 homoflavanol, flavonoids, kaempferol, quercetin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 homoflavanol, flavonoids, kaempferol, quercetin