348 PIGMENTS 



Kostanecki * ; the way in which the change was effected may 

 be seen from the following formulae : — 



H Cl 



HO— r Y 1 < )— OH HO- 



+ 2H + HCl-> 



iH 



Intermediate reduction compound. 



The latter by loss of water yielding — 



Cl 



/ OH 



O / 



HO-^\/\_X~^_OH 



-OH 



CH 

 OH 



Cyanidin chloride II. 



This may be experimentally verified by carefully adding 

 magnesium powder to a solution of quercetin in a mixture of 

 five volumes of alcohol with one volume of concentrated 

 hydrochloric acid, when a rose-pink rapidly develops. f 



It has been pointed out on page 338 that the evidence 

 from the plant shows that there is some fairly close relation- 

 ship between carbohydrates and anthocyanin production ; it 

 was suggested by Robinson % that the C15 nucleus of the 

 anthocyanins, flavones and flavonols, might be derived from 

 the union of two molecules of glucose connected together by 

 aldol condensations with glycerose (dihydroxy acetone). On 

 the other hand, a different point of view with regard to the 

 significance of carbohydrates in contributing to the formation 

 of anthocyanins is offered by Goodyear and Haworth § who 

 draw attention to the fact that the pyran residue — 



* Kostanecki : " Ber. deut. chem. Gesells.," 1904, 37, 1402. 

 t Everest : " Proc. Roy. Soc," 1914, B., 87, 444. 

 X Robinson : " Brit. Assoc. Reports," Edinburgh, 1921. 

 § Goodyear and Haworth : "J. Chem. Soc," 1927, 3141. 



