CAROTENOLS AND OXYCAROTENOLS OF THE C40 SERIES 567 



tetraacetate by the Criegee method, it is not attacked; this indicates that 

 the hydroxyls are not on adjoining carbon atoms. ^^^ Since on decomposi- 

 tion with permanganate viohixanthin yields a:,a-(hmeth}'lsuccinic acid, just 

 as do lutein and zeaxanthin, it is believed that it has a corresponding ring 

 system. 



Like other epoxides, \'iolaxanthin is extremely susceptible to acid. In 

 the presence of a low concentration of hydrochloric acid, or when dissolved 

 in chloroform, it is converted to the difuranoid compound auroxanthin. 

 For a discussion of this compound as well as for a comparison of the proper- 

 ties of violaxanthin with those of auroxanthin, see the next section (Section 

 (7) ). The conversion of violaxanthin to mutatoxanthin, which has also been 

 observed, must involve a preliminary removal of one of the epoxide groups. 



b. Occurrence. In addition to the yellow pansy, a number of other 

 (lowers contain violaxanthin, as well as lutein. These include Tragopogon 

 pratensis (goat's beard). Laburnum anagyroides (golden chain), Brassica 

 Kaber {Sinapis officinalis) (field mustard),^"'* Arbutus unedo (strawberry 

 tree),-^^ Iris pseudacorus (yellow iris),^* and probably also Ranunculus 

 acris (butteix'up).^^'^ Other flowers listed as sources of violaxanthin are the 

 Tidipa spp. (yellow tulip), -'^ Ulex europaeus (furze), -^^ Calendula officinalis 

 (calendula) ,^^ Tagetes grandiflora (giant marigold), ^^* Tussilago farfara 

 (coltsfoot). ^^^ Violaxanthin has also been found with taraxanthin in the 

 dandelion (Taraxacum offlcinale).^^* The presence of violaxanthin in the 

 flowers of the Crepis aurca (orange hawksbeard) and of the birdsfoot 

 trefoil, Lotus corniculatus (yellow cat's clover) has recently been noted. ^"^ 

 Kulm and co-workers^'* have demonstrated the presence of violaxanthin in 

 the green leaves of Aesculus hippocastanum (horsechestnut) . 



Fruits, likewise, sometimes contain violaxanthin. This is true of the 

 fiTiit pulp of the giant squash (gourd) {Cucurbita niaxima)^^^ as well as of 

 the Citrus poonensis and the papaya or paw paw (Carica papaya) .^^-^^^ 

 Other fruit sources include the Seville orange [Citrus auraulium)^^^'^^'^ and 

 the persimmon (Diospyrus costata).-^^ 



(7) Auroxanthin 



Karrer and Rutschmann^^' observed a new pigment on chromatographic 

 separation of the carotenoids in the wild pansy (Viola tricolor). They 

 called this substance "auroxanthin" because of its golden j^ellow ciystals. 

 Although it was first found in the pansy, it has been observed in most in- 

 stances where violaxanthin occurs. 



The nature of auroxanthin became evident when Karrer and Jucker^'^ 

 proved it to be the difuranoid derivative of violaxanthin. As indicated 



"8 p. Karrer and R. Morf, Helv. Chim. Acta, 16, 863-864 (1932). 



*^' L. Zechmeister and P. Tuzson, Naturwissenschaften, 19, 307 (1931 ). 



"" P. G. F. Vermast, Naturwissenschaften, 19, 442-443 (1931). 



3" P. Karror and J. Rutschmann, Helv. Chhn. Ada, 25, 1024-1027 (1942). 



