v] CONSTITUTION OF ANTHOCYANINS 69 



Wheldale (244, 254), 1913, 1914. The flower-pigment of 



Antirrhinum ma] us. 



The anthocyanin pigment, as in most flowers, is only present in 

 the epidermis, while the inner tissues contain a flavone, from which, 

 we have reason to believe, the anthocyanin is derived. Pigment was 

 prepared separately from the following varieties (see p. 160) : magenta 

 (various shades together), ivory tinged with magenta, crimson, rose 

 dore (various shades) and bronze (various shades). In the magenta 

 and rose dore series, apigenin is present in addition to anthocyanin ; 

 in the crimson and bronze, both apigenin and a second pigment, luteolin 

 (see p. 114). All the flowers have, in addition, a patch of deep yellow 

 pigment on the palate. The latter pigment can be eliminated, if desired, 

 by tearing away the lower half of the flower, and using the upper half 

 only for extraction ; this device was adopted in the preparation of some 

 samples of pigment. Thus, in any method of extraction, we have to 

 deal, not only with an anthocyanin pigment, but also with one or more 

 accompanying flavones. Two anthocyanins were found to be respon- 

 sible for the colour varieties, viz. a true red anthocyanin in the rose 

 dore and bronze series, and a magenta (blue-red) anthocyanin in the 

 magenta and crimson series. The following method was employed 

 for obtaining the pigment in quantity. 



The flowers are boiled with water in saucepans, and the water 

 extract filtered through large filters into lixiviating jars. The antho- 

 cyanins and flavones are then precipitated as lead salts by adding solid 

 lead acetate to the hot solution until no more precipitate is formed. 

 (The colour of the precipitates varies according to the flowers used; 

 it is blue-green for full-coloured magenta, yellow-green for tinged ivory, 

 dirty red for rose dore, and so forth. The colour of the lead salt of the 

 anthocyanin is obviously modified by the amount and colour of the 

 lead salts of the accompanying flavones.) The lead precipitate is 

 filtered off, a vacuum pump being used for filtration ; the solid cake of 

 lead salt is then decomposed with 5-10 % sulphuric acid. The lead 

 sulphate is filtered off, and a bright red solution of the pigments is 

 obtained. This solution contains all the pigments in the flower used, 

 both anthocyanin and flavones, in the form of glucosides in dilute acid 

 solution. The solution is now boiled in a large Jena flask, fitted with a 

 reflux condenser, for several hours. On cooling, the anthocyanin and 

 flavones, now less soluble and no longer in the form of glucosides, 

 separate out as a dark purplish- or brownish-red powder, according 



