FLAVONE DERIVATIVES 



245 



CH CO CH 

 Xanthone 



YELLOW COLOURING MATTERS DERIVED FROM FLAVONE. 



There are quite a considerable number of yellow substances 

 occurring in plants derived from flavone, but only a few re- 

 presentative ones will be mentioned here in order to give some 

 idea of the constitution of these compounds. 



Ckrysin, or dihydroxy-flavone, is a yellow colouring matter 

 occurring in several varieties of poplar, such as Populus nigra 

 and P. pyramidalis. 



o 



HOI r c- 



CH 



\/\ / 



OH CO 



Quercetin, or tetrahydroxy-flavonol * 



OH 



HO 



OH 



occurs with rhamnose in the form of a glucoside in the bark of 

 Quercus tinctorius, in the leaves of the horse-chestnut and hop, 

 and in many other plants. Quercetin, in the uncombined 



* Flavoncl is the hydroxyl derivative of" flavone ; the relationship between 

 the two substances is shown by the following formulae : 





O 



\/\ 



CH 



CO 



Flavone 



\ 



c- 



\x\ 



OH 



CO 



Flavongl 



