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CHEMISTRY OF PLANT LIFE 



83), known as "anthocyanidins," remain. These anthocyanidins 

 are themselves pigments. They have been shown to be all deriva- 

 tives of the anthocyan nucleus. The oxygen atom in this nucleus 

 is very strongly basic and exhibits its quadrivalent property by 

 forming stable salts by direct addition of acid radicles. The 

 variation of color of the anthocyanins has been explained by 

 Willstatter, as follows; the red is the acid salt, the blue is a neu- 

 tral metallic salt, and the violet is the anhydride of the antho- 

 cyanidin in question, thus 



Cl Cl 



Violet 



All of the natural anthocyanin pigments appear to contain a 

 chlorine atom attached directly to the ring oxygen, as shown in the 

 above partial formulas. In addition, they have four, five, or six 

 hydroxyl (OH), or methoxy (OCHs), groups attached at various 

 points around the three rings. The following formula for cenidin, 

 one of the most complex of these anthocyanidins, will illustrate 

 their structural arrangement. 



Cl 



OH 



Delphinidin is the corresponding compound without the two 

 CHs groups; while cyanidin contains only five OH groups; and 

 pelargonidin, only four OH groups. 



