Miss Wheldale, On the nature of anthocyanin. 137 



On the nature of anthocyanin. By Miss M. Wheldale, 

 Newnham College. (Communicated by Professor Bateson, F.R.S.) 



[Read 8 March 1909.] 



Many investigators have suggested, from time to time, that 

 a relationship exists between the widely distributed tannins in 

 plants and the equally widely distributed pigment known as 

 "anthocyanin," Curtel\ Dennert^ Gautier^ Ichimura*, 

 MIRANDE^ Newbigin^ Wiesner^ Wigand^ and ZoPF^ among 

 others, mention the occurrence of a colourless chromogen, of the 

 nature of a tannin, in tissues, which eventually may become 

 coloured with anthocyanin; the colouration arises under the 

 influence of various agents, such as nutrition, temperature, light, 

 and injury, either mechanical or such as is brought about by 

 attacks of fungi, etc. The process of transition, moreover, from 

 chromogen to pigment has been regarded as one of oxidation. 



Not only has the above relationship been established, but the 

 view has also been held that anthocyanin itself is some compound 

 of a tannic acid. 



Overton^", for instance, from the increased production of 

 anthocyanin brought about by artificial feeding of plants with 

 carbohydrates, arrived at the conclusion that this pigment may 

 very possibly be a sugar compound of a tannic acid, that is a 

 glucoside. 



Gautier^^ also isolated various colouring matters from the 

 red leaves of the Yine and he regards these pigments as coloured 

 tannic acids. 



Pfeffer^^, in a general review of the subject, states that the 

 red and blue pigments dissolved in the cell-sap, such as anthocyanin, 

 seem to be tannins or compounds allied to phenols, though in his 

 view they may also be derived from other substances since they 

 often occur in plants which contain no tannin. 



Heise^^ in addition, isolated two pigments from the Bilberry 

 and showed one to be the glucoside of the other. Both substances 

 appear to be aromatic compounds though they have not directly 

 been proved to be tannins. 



The word tannin is a somewhat difficult term to define; 

 it is used in general for a class of substances very widely 

 distributed in plants and having certain properties in common. 



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