ANTHOXANTHINS 



339 



OH CO 



Quercitin 



or 



i 3 3'. 4'-tetrahydroxy- 

 flavonol. 



OH 



3* 2', 4'- 

 tetrahydroxy- 

 flavonoL 



CH 3 



OH 



Myricetin 

 or 



i, 3, 3', 4', 5'- 

 pentahydroxy-flavonol. 







Euxanthone 



or 



2, 3'-dihydroxy- 

 xanthone. 



OH 



OH CO 



Gentisin 



or 



4-methoxy- 

 2, 3 / -dihydroxy- 

 xanthone. 



These pigments thus contain the simple aromatic compounds, benzene, 

 phenol, catechol, resorcinol or pyrogallol combined with benzo-y-pyrone. 

 On decomposition they yield polyhydroxybenzoic acids (protocatechuic, 

 hydroxybenzoic, or resorcylic) and the above phenols. Their formulae have 

 been arrived at by the study of these decomposition products and have been 

 proved by synthesis. The details of the products of decomposition and the 

 synthesis are given in the larger text-books of organic chemistry. 



Chrysin occurs in various species of poplar and mallows. 



Apigenin occurs in parsley and celery in the form of the glucoside, apiin. 



Luteolin is the yellow colouring matter of weld or dyer's broom. 



Galangin is found in the root of Galanga. 



Caempferol is contained in Galanga root and combined with rhamnose 

 as the glucoside, caempferitrin, in Java indigo. 



Fisetin is present in Fiset wood (Rhus cotinus] and Quebracho wood 

 (Quebracho Colorado). 



Quercitin is found with fisetin and also as glucoside, with rhamnose, in 

 oak bark (Quercus tinctoria). It is present in the flowers of the horse- 

 chestnut and in the skin of onions. 



Morin is a constituent of yellow wood (Morus tinctoria). 



Myricetin is the yellow pigment in the bark of Myrica nagi. 



Euxanthone is formed when cattle are fed with mango leaves and is 

 excreted in combination with glycuronic acid as euxanthic acid (Indian 

 yellow). 



Gentisin is the yellow pigment present in Gentiana lutea. 



These pigments are yellow crystalline solids, very slightly soluble in 

 water. They dissolve in acids giving yellow or yellowish-red solutions ; 

 they also dissolve in alkalies giving solutions which are yellow or reddish. 

 Some of them give a dull green or red-brown coloration with ferric chloride. 



