FLAVONE DERIVATIVES 



243 



CH 



CH 



CH 



ti I I 



CH 



CH 



\ 



CH CO CH 



X&nthone 



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. 



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

 occurring in several varieties of poplar, such as Populus nigra 

 and P. pyramidalis. 



O 

 \ 



H( 



:H 



OH CO 

 Quercetin, or tetrahydroxy-flavonol 



O 



/\ / 



HOi 



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 of flavone ; the relationship between 

 the two substances is shown by the following formulas : 



\ 



rO 



CH 



Flavone 



COH 



CO 



Flavonol 



16* 



