THE ANTHOCYAN PIGMENTS 



By ARTHUR E. EVEREST, M.Sc, Ph.D., Univ. Coll., Reading. 



The name Anthocyan appears to have been introduced by 

 Marquart {Die Farben der Bliiten, Bonn, 1835) to designate the 

 blue pigments present in flowers. Later there arose the belief 

 that the red and purple flower pigments were all merely another 

 form of the same blue anthocyan — or, as Fremy and Cloez styled 

 it, cyanin — and that the variation of colour was merely due to 

 the nature of the cell sap ; this resulted in the name anthocyan 

 being indiscriminately applied to all of them. The present use 

 of the term anthocyan as designating a large class of naturally 

 occurring plant pigments gradually became general, as, from 

 time to time evidence accumulated to show that the red, purple, 

 and blue pigments differed considerably among themselves. 



The rapid and very important advances that have taken place 

 in this field of research during the last decade make it advisable 

 to deal more fully with this latter phase of the work than is neces- 

 sary with the work that preceded it, but at the same time the 

 qualitative work of earlier investigators needs due recognition. 



As early as 1836, Hope, in a paper read before the Royal 

 Society of Edinburgh (March 21 ; oi.Journ.f.pr. Chem. (10), 269, 

 (1837), concluded, as the result of experiments on a large number 

 of different kinds of flowers, that the pigments, or chromules, 

 present were formed from faintly coloured chromogens, by a 

 variety of changes. Of these chromogens, according to Hope, 

 there were two types, one called by him Erythrogen, which by 

 the action of acids yielded red pigments, and a second, named by 

 him Xanthogen, which with alkalies gave rise to yellow pigments. 

 He concluded that, in orange, red, purple, and blue flowers both 

 were present, whereas in yellow and white flowers only xan- 

 thogen was found. From his examination of leaves, he concluded 

 that chlorophyll was accompanied by xanthogen, but that, 

 excepting in cases where reddening was obvious — e.g. autumn 

 leaves — no erythrogen was present. 



In the following year, Berzelius (Annalen, 1837, 21, 262) 



597 



