330 



Dr. A. E. Everest. 



anfchocyans from flavonol derivatives. Willstatter agrees with the author 

 with regard to the structure of the anthocyan molecule, and further, his 

 analytical results (loc. cit.) have shown that the colourless iso-forms are 

 produced by the addition of one molecule of water to the anthocyan molecule ; 

 this is in agreement with the above scheme. 



As flavone derivatives, which also occur in plants, yield somewhat similar 

 red pigments, it seems probable that further examination of the natural 

 anthocyans may yield compounds related to this class of pigment. Again, no 

 natural anthocyan pigment has as yet been examined in which the hydroxy- 

 groups in the phenyl group attached to the benzo-pyran residue are in the 

 nieta-position to one another. As morin, a flavonol of this type, occurs 

 naturally, and on reduction yields a red pigment, it is possible that natural 

 anthocyans of this type may be among the fruits of further research on these 

 pigments. It is quite likely that such compounds would differ slightly from 

 those at present investigated. 



Apart from the anthocyan question, the observations recorded, appear to be 

 of interest, in that, as in every case where the author obtained an anthocyan 

 by reduction of the flavone or flavonol present in flower extracts, he was able 

 to show that the pigment was an anthocyanin — glucoside — it would follow 

 that in each case the flavone or flavonol derivative in the plant must have 

 been present in the form of a glucoside. 



Experimental. 



The methods of obtaining anthocyanins and anthocyanidins from flavonol 

 derivatives by reduction have already been described by the author {loc. cit.). 

 The method which gave most satisfactory results, viz. : reducing the compound 

 dissolved in a .mixture of 5 vols, absolute alcohol and 1 vol. concentrated HC1 

 by means of magnesium (ribbon or turnings), was then used only when pure 

 or nearly pure yellow compounds were obtainable. By slight adaptation, 

 however, it has been found possible to use it with advantage in many cases 

 when dealing with plant extracts. It is only necessary to add to the extract 

 of the yellow pigment in 2N HC1 its own volume of concentrated HC1 and 

 then to the whole 4-5 times its volume of absolute alcohol, for the reduction 

 with magnesium to proceed readily. In some cases it has been found 

 advantageous to add a drop or two of concentrated HC1 from time to time. 

 A disadvantage of this method is the somewhat considerable dilution which 

 results. 



Aqueous solutions of the red pigments produced may be obtained from the 

 aqueous alcoholic solutions above mentioned, by the addition of much ether, 

 and if necessary, a small quantity of dilute acid. The red pigments are left 



