222 



APPENDIX 



The flower-pigment of the Peony, Paeonia (Willstatter & Nolan, 644). 

 The dried and powdered flowers are digested with methyl-alcohol- 

 hydrochloric acid (2 %), and the extract precipitated with ether. The 

 crude pigment is purified by various processes, and finally crystallised 

 as the chloride from boiling N/2 hydrochloric acid. Paeonin, on hydro- 

 lysis by boiling with 20 % hydrochloric acid, yields paeonidin and two 

 molecules of dextrose. Paeonidin is a mono-methyl ether of cyanidin, 

 and is converted into the latter on treatment with hydriodic acid. 



Some of the properties of the above anthocyanins are set out in the 

 accompanying table (see pp. 220, 221), but the original papers should 

 be consulted for fuller details. 



In a further publication (Willstatter & Zechmeister, 628), Will- 

 statter describes the preparation of synthetic pelargonidin. The 

 synthesis is carried out first by the action of 3:5: 7-trimethoxy- 

 coumarin and magnesium anisyl bromide. The resultant product is 

 next treated with hydrochloric acid which gives anisyltrimethoxy- 

 pyryliumchloride : 



OCH 3 



OCH, 



CH,0 



The product is then demethylated, and finally the iodide is con- 

 verted into the chloride. The compound obtained, oxyphenyl-trioxy- 

 benzopyryliumchloride, is shown to be identical with the chloride of 

 pelargonidin by analyses, crystalline form, absorption spectra, solu- 

 bilities and qualitative reactions. This result, though it determines 

 the constitutional formula for pelargonidin, does not unfortunately 

 give any clue to the course of synthesis in the plant. 



Some of the most important of these later results are those con- 

 cerned with the isolation and analysis of flower-pigments of different 

 colour-varieties of certain plants (Willstatter and Mallison, 639). 

 Briefly the genera and species examined are: 



Centaurea Cyanus. The dark purple-red variety contains neutral 

 cyanin, and the blue type the potassium salt of cyanin as previously 

 stated. But the pink variety was found to contain pelargonin identical 

 with the pigment of the scarlet Pelargonium. 



