FLAVONE DERIVATIVES 



245 



CH O 

 CH C 



CH 



CH 



Flavone 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. 



C/uysin, or dihydroxy-flavone, is a yellow colouring matter 

 occurring in several varieties of poplar, such as Popnlics nigra 

 and P. pyraniidalis. 



H0/\/°\ 



CH 

 OH CO 



Quercetin, or tetrahydroxy-flavonol * 



O OH 



HO 



/\/ 



OH 



COH 



OH CO 



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 



*Flavonol is the hydroxyl derivative ol flavone; the relationship between 

 the two substances is shown by the following formulae : — 



/\/ 



r<Z> 



CH 



\/\ / 

 CO 



Flavone 





OH 



\/\ 



CO 



Flavonol 



