362 Chemistry of Aiit/iocyati Plgmetitx in Plants 



much that is of interest to those studying these pigments tiimi the 

 standpoint of genetics. 



The corn-flower pigment, which was obtained pure and cr3'stailine, 

 was proved to be a glucoside, which on hydrolysis with acids yielded 

 two molecules of glucose and one molecule of the true pigment — a fine 

 crystalline substance — and it was also shown that in all the cases 

 examined the pigments occurred in the jjlants only as glucosides. These 

 results have been fully confirmed by later work, and the idea, so fre- 

 quently put forward, that the pigments occur together in plants both as 

 glucosides and non-glucosidcs, must as a result be abandoned. In cases 

 where previous workers obtained mixtures of glucoside and non-glucoside, 

 e.g. Heise, Glan, it was due to partial hydrolysis during the processes of 

 isolation. This generalisation simplifies somewhat the problems to be 

 dealt with when the processes going on within the plant tissues come 

 to be considered, but by no means so much as the proof that the blue 

 anthocyan pigments are alkali salts of compounds which in the free 

 state are violet or violet-red in colour, and which are capable of uniting 

 with acids to form oxonium salts which are red in colour. Beyond these 

 results the same authors demonstrated that, at least in the case of the 

 corn-fiower pigment, the decolourisation which so readily takes place in 

 aqueous solution was not due to reduction as has been assumed so 

 frequently. It was further shown that by oxidation the pigment of the 

 corn-flower readily passed to a yellow pigment which had properties 

 similar to those of the fiavone or flavonol derivatives. 



This work brought the present author to the opinion that the 

 anthocyans were reduction products of the fiavone or flavonol com- 

 pounds, whereas Willstatter favoured rather the idea that they were 

 related to some unknown flavone or flavonol derivatives in which a 

 hydroxyl group occurred in the benzopyrone nucleus in the para 

 position to the linkage of the oxygen atom of the pyrone ring. The 

 relationship is clearly shown by the formulae I and II, and it will be 

 seen that this makes the anthocyan an oxidation product of the com- 

 pound II. 



OH 



■Ch 



HO- 



MO 



I. Antliocyau. II. Flavone derivative. 



