66 THE BOTANICAL MAGAZINE. [Vol. xxxi, No. ses, 



Anthocyanin, however, is found to be a compound of a very 

 unstable nature and is easily decomposed to a colourless compound 

 when it is mixed with the plant juice which contains oxidising 

 enzymes. Even the aqueous solution of hydrogen peroxide and 

 potassium permanganate when they are added to the aqueous 

 or alcoholic extract of anthocyanin respectively, the anthocyanin 

 is readily decomposed to a colourless compound. Kastle and 

 Hoden 1 have shown that the blue flower of Cichorium intybus 

 is changed to white by the action of oxidase which is contained 

 in the petal. Furthermore, they have shown that the extracted 

 sap is readily decolourized by the oxidase prepared from the 

 potato, and even by such substances as potassium perman- 

 ganate, potassium ferricyanid, quinone, a dilute solution of 

 iodine, and by a solution of hydrogen peroxide and the influence 

 of various catalysts such as platinum black, manganese dioxide 

 and lead peroxide. Similar observations . are made by Atkins 2 

 on Iris, and by Combes 3 on Ampelopsis. 



My own observations agree with those above cited. It can 

 be done in a simple manner by mixing a plant juice which is 

 active in oxidising power, such as that of potato tuber, or of 

 certain mushrooms like Armillaria edodes or Lactaria Hatsu- 

 dake, and the aqueous extract of anthocyanin. When the 

 mixture is kept at room temperature, the colour gradually 

 diminishes and at the end of one hour or so the mixture 

 becomes almost devoid of colour. Such a mixture no longer 

 gives a typical anthocyanin colour-reaction by an addition of 

 acid or alkali. When the plant juice is boiled before it is to be 

 mixed, the colour of the mixture remains unchanged, and by 

 the addition of a drop of acid, a deep red colour is produced. 

 A weak solution of hydrogen peroxide instead of the plant 

 juice, also has the same effect. In the latter case, even in a 

 strong acid or alkaline solution, decolourization goes on without 

 any hindrance. 



1 Kastle, J. H. and Hodes, E. D.: Am. Chem. Jour. 46: 315, 1911. 



2 Atkins: Loc. cit. 227. 



3 Combes, E.: C. E. Acad. Sci. Paris. 157: 1454, 1913. 



