104 On a Supposed Synthesis of Anthoqjanin 



glucosides), the reactions controlling the formation of anthocyanin might 

 be as follows : 



glucoside (of tlavone) + water ±^ chromogt'n (tlavime) -/- /2-tx^,<*^ 

 "Frrrrr^r y ( flavone) + oxygen = anthocyanin'. 



It was suggested that one or more hydroxyls, though not necessarilij 

 all, of the flavones were combined with sugar and that after hydrolysis 

 of certain, though again not all, of the hydroxyls, further changes, such 

 as oxidation or condensation, or both, might take place at these points 

 thus opened to attack, with the formation of anthocyanin. Hence the 

 anthocyanins themselves would be glucosides, and at no time would the 

 products taking part in the reaction be completely in the nonglucosidal 

 state. 



The first criticism offered by Everest is that there are no known 

 glucosides of the flavones having more than one or two hydroxyl gi-oups 

 substituted by sugar molecules. The hypothesis was brought forward 

 in full knowledge of this fact, but it must be borne in mind that no 

 accurate work has been done with a view to actually ascertaining the 

 number of sugar molecules attached to flavones in the plant. Certain 

 stable glucosides of various flavones, with only one or two sugar mole- 

 cides attached, have, from time to time, been extracted and identified, 

 and probably the fact that they could be identified is due to their 

 stability. It is quite conceivable that, gi'eater precautions being taken, 

 other and less stable compounds might be isolated. No special pre- 

 cautions have in fact been taken, certainly in the majority of cases, to 

 avoid decomposition of possible unstable glucosides. Until further 

 investigations have been carried out on this point, no definite statement 

 can be made as to the number of sugar molecules attached to flavones 

 while in the plant. 



The second criticism offered by Everest is based upon a misconception 

 of the hypothesis. According to the evidence of Willstatter and Everest'', 

 anthocyanins (as glucosides), can be distinguished from anthocyanidins 

 (non-glucosides), by their solubility in amyl alcohol, the anthocyanidins 

 being soluble. 



Hence if the flavones are completely hydrolysed and then give rise 

 to non-glucosidal anthocyanin (which is an incorrect interpretation of 

 Wheldale's hypothesis) it should be possible to isolate anthocyanidins 



1 The second equation is incorrectly quoted in Everest's paper, no allowance being made 

 for condensation. 



2 Everest, loc. cit. 



