THE OXIDASES IN RELATION TO PIGMENTATION 271 



SOME SOURCES AND PROPERTIES OF PURE 

 ANTHOCYANINS. 



As a source of anthocyanin, Willstatter and Everest 

 (1913) have recently employed the cornflower. 



The blue pigment was by them proved to be the potas- 

 sium salt of an acid (cyanin), which is violet in the free 

 state, whereas the red pigments are combinations of cyanin 

 with simple organic acids to form oxonium salts. These 

 workers attributed the various shades of colour in the 

 flower to such substances. Willstatter and Everest are 

 of the opinion that cyanin is a flavone derivative, and that 

 all anthocyanins are present in the living cell as glucosides. 



Willstatter (1914), in conjunction with various collabor- 

 ators, distinguishes anthocyanins, which are glucosides, 

 from anthocyanidins in which the carbohydrate side-chain 

 has been split off. The former are decolorized by cold 

 alcohol, whereas the latter are stable in the cold, but 

 decolorized on warming. In both the colour is restored by 

 acids, though Everest (1914, 2) states that this is not so 

 easily effected with the anthocyanidins. Futhermore, 

 anthocyanins are not extracted by amyl alcohol from 

 dilute aqueous sulphuric acid, whereas anthocyanidins are 

 quantitatively taken up by the alcohol. These can be dis- 

 tinguished inter se by their colours, their solubilities, and 

 the reactions they give with ferric chloride. Anthocyanins 

 are most readily identified by their specific rotations, which 

 are very high from 200 to 1,400. 



Cyanin on hydrolysis gives cyanidin (the hydrochloride 

 of which has the formula C 15 H 11 6 C1) and two molecules 

 of glucose. The pigment of the cranberry also gives 

 cyanidin, and one molecule of galactose, whereas Rosa 

 gallica gives cyanidin and two molecules of glucose. 

 When heated with alkali to a higher temperature, cyanidin 

 gives phloroglucinol and protocatechuic acid. 



