ANTHOCYANINS 249 



colouring matter of the cornflower CeiUaurca cyanus and of 

 Rosa gallica ; closely related to this substance are the antho- 

 cyanins of the cranberry (idaein), the bilberry (myrtillin), of 

 blue grapes (oenin), of Delphinium consolida (delphinin), and 

 of Pelargonium zonale, var. meteor (pelargonin), Althaea rosea 

 (althaein), Malva sylvestris (malvin). 



The anthocyanins are all glucosides, and on hydrolysis 

 yield one or more molecules of a carbohydrate, together with 

 a so-called anthocyanidin, which compound, unlike the parent 

 substance, is soluble in amyl alcohol. On these facts is based 

 what is known as the anthocyanin reaction, according to which 

 a solution of the substance in sulphuric acid yields nothing to 

 amyl alcohol, but after hydrolysis the resulting anthocyanidin 

 may be extracted from the solution quantitatively by amyl 

 alcohol. 



The products obtained by the hydrolysis of the various 

 anthocyanins so far investigated are given in the following 

 list :— 



Cyanin yields Cyanidin + 2 mols. glucose. 



Idasin yields Cyanidin + i mol. galactose. 



CEnin yields CEnidin + i mol. glucose. 



Myrtillin yields Myrtillidin + i mol. glucose. 



Delphinin yields Delphinidin + 2 mols. glucose + 2 mols. p. 



hydroxybenzoic acid. 

 Pelargonin yields Pelargonidin + 2 mols. glucose. 



The anthocyanidins or non-carbohydrate moiety of the 

 anthocyanins are derivatives of benzo-pyrilium which, as may 

 be seen from the appended formula I., 



CH O CH O 



/ \/ \ / %/ \ 



CH C CH CH C CH 



II I II II I II 



CH C CH CH C CH 



\ /\ / \ /\ / 



CH CH CH CO 



I. n. 



is closely related to benzo-pyrone II., the mother substance of 

 the flavones. Both these substances contain a so-called basic 

 oxygen atom which by becoming tetravalent can form addi- 

 tive compounds with acids producing oxonium salts. These 

 salts in the case of the fiavones are not stable and do not 

 occur in the plant, but the anthocyanidins yield stable oxonium 



