Wakeman—Pigments of Flowering Plants. 
827 
HC 
HOC 
O 
OH OH 
II i I 
C—CH CH 
' C 
HC 
CH 
/\ 
COH 
CH 
CH 
Both the above formulas have, however, six hydroxy groups, 
whereas vitexin forms only a pentacetyl and saponarin only a 
nonaeetyl derivative. Dehydration might, however, take place 
in the molecule during the process of acetylation. 
To account for the formation of only the pentacetyl vitexin 
Perkin has suggested the presence of a reduced phloroglucinol 
nucleus. This would give a formula of the type shown below. 
Pigments referable to hydrocarbons of the formula of sat¬ 
uration CH 2n - 16 . 
Of all the pigments of known constitution occurring in plants 
by far the greater number are referable to hydrocarbons of the 
formula of saturation C n H 2 n_ 16 . These pigments when referred 
to their underlying hydrocarbons fall into three classes. 
1. ) The diphenyl olefin derivatives. 
2. ) The dihydroanthracine derivatives. 
3. ) The methyl-phenyl hydrindine derivatives and their 
oxidation products. 
In the first class are found the flavone derivatives, referable 
to diphenyl propene, and a large number of compounds refer¬ 
able to similar hydrocarbons. This group also includes the so- 
called anthocyanine pigments, so far as their structure has been 
determined. 
The second class is made up of the anthraquinone and methyl 
anthraquinone derivatives, a group which includes, outside of 
the flavone derivatives, of the above class, the greater number 
of coloring matters, so far studied, falling under this degree of 
saturation. 
