106 On a Supposed Sf/nt/iem's of Anthocyanin 



Moreover the fact that both natural aiitliocyaniii and the artificial 

 red products can be reduced to a colourless form and then reoxidised to 

 the coloured state, cannot be taken as proving that the artificial sub- 

 stance is anthocyanin, since innumerable coloured aromatic substances 

 give leucoconipounds on reduction which regain their colour on oxidation. 



The grounds for thinking tliat these substances are anthocyanins 

 seem to us slight, and our observations lead us, in the absence of further 

 evidence, to feel considerable doubt on the point for the following 

 reasons : 



1. The rod product from (juercetin is soluble in ether whereas all 

 natural anthocyanins are quite insoluble in this solvent. 



2. The only case in which anthocyanins and their antecedent 

 chromogen have been analysed is that of Antirrhinum, and here the 

 anthocyanins are oxidised, and not reduced products, of the flavone 

 concerned, i.e. apigenin'. 



3. When apigenin is treated in alcoholic solution with sodium 

 amalgam and acid, as was done with quercetin, we obtained a red 

 product and the reaction clearly followed a similar course in the two 

 cases. Analyses showed the product from apigenin to be a reduced 

 substance and its reactions with acids and alkalies do not in any way 

 resemble those of anthocyanin. With alkalies the red colour is deepened 

 and with acids the red colour becomes yellowish. 



Since, in the case of apigenin, the product is certainly not an antho- 

 cyanin, it obviously throws doubt on Everest's assumption that the 

 similar products from quercetin and other flavones are anthocyanins. 

 Thus, in the only case where the flavone and the naturally derived 

 anthocyanin have been isolated, the product formed by reduction of the 

 same flavone is quite a different substance from the natural anthocyanin. 



The evidence of a considerable amount of work by Keeble, Armstrong 

 and Jones^ shows that in the vegetative organs as well as in the flowers 

 of various plants the distribution of anthocyanin coincides with the 



' Wheldale, M. and Basset, H. LI., "The Flower PignientB of Antirrliiniim niujiis. 

 3. The Red and Magenta Pigments," Biochemical Juuiii., 1913, Vol. vii. p. 87. 



- Keeble, F. and Ainistionp, E. F., " The Distribution of Oxydases in Plants and their 

 Role in the Formation of Pigments," Roy. Soc. Proc, 1912, B, Vol. i.xxxv. p. 214 : " The 

 Role of Oxodases in the Formation of the Anthocyan Pigments of Plants," Journal of 

 Genetics, 1912, Vol. ii. p. 277: Keeble, F., Armstrong, E. F., and Jones, W. N , "The 

 Formation of the Anthocyan Pigments of Plants. Part 4. The Chromogons," Hoy. 

 Soc. Proc, 1913, B, Vol. i.xxxvi. p. 308: "The Formation of Anthocyan Pigments 

 of Plants," Part G, Roy. Hoc. Proc, 11113, B, Vol. i.xxxvii. p. 113. 



