MISCELLANEOUS COMPOUNDS 277 



biochemical criteria in systematics. Betacyanins have traditionally 

 been called "nitrogenous anthocyanins." As far back as the nineteenth 

 century these compounds were regarded as different from the typical 

 anthocyanins. Moreover, the compounds were found only among 

 several families of the order Centrospermae. Although further chemi- 

 cal properties of the pigments were described periodically, only within 

 the past five years has there been any clear recognition that the 

 nitrogenous anthocyanins are not true anthocyanins. Schmidt and 

 Schonleben (1956) and Linstedt (1956) discovered the presence of acid 

 groups in the nitrogenous anthocyanins. Wyler and Dreiding (1959) 

 have subsequently shown that the compounds are not flavonoids. The 

 latter authors, upon degradation of betanin, obtained indole and pyri- 

 dine derivatives. 



The Dreiding group has recently established the skeleton for 

 betanidin, the aglycone of the red-violet beet pigment, betanin 

 (Mabry et al., 1962). They have proposed the following structure for 

 the hydrochloride of betanidin: 



HO 



CO2CH3 



HaCOaC-^^N^^COsCHa 

 H®C1© 



The proposed structure contains a cyanine-dye type of chromophore. 

 Other interesting structural features include the presence of dihydro- 

 indole and dihydropyridine rings. The glucose is attached at one of the 

 two phenolic hydroxyl groups in the natural product, betanin. Obvi- 

 ously, there is no relationship between the betacyanins and antho- 

 cyanins, or flavonoids in general. Despite the lack of any overt 

 physiological activity in animals the substances may best be con- 

 ceived of as alkaloids. The elucidation of the structure of this new class 

 of natural pigments represents a significant contribution to plant 

 chemistry and to chemical systematics. 



The systematic significance of this group of compounds has 

 been evaluated by various authors (Lawrence et al., 1941; Gibbs, 

 1945; Reznik, 1955, 1957; Wyler and Dreiding, 1961; Rauhand Reznik, 

 1961; Mabry et al., 1963). The betacyanins occur in eight families of 

 the Centrospermae (Table 14-2). In the families Nyctaginaceae and 

 Cactaceae the presence of betacyanins has been a factor in favor of 

 placement of these families in the Centrospermae. Surprisingly, one 



