B CAROTENOIDS IN ANIMALS 93 



elucidated in one case: zoofulvin has been identified with xanthophyll. The 

 structure of picofulvin, on the other hand, is still unknown. 



(ii) Carotenoids from fat tissues, foot skin, body skin and beaks 



It was mentioned above that no carotenoid, or other polyene pigment of 

 hydrocarbon nature, has been found in bird feathers. By contrast, the beaks 

 and skin of various animals contain mixtures of carotene and xanthophyll. 

 At an early date, Krukenberg^^ established the presence of lipochromes in 

 the fat tissues and foot skin of many animals. In 1930, Lonnberg^^ showed that 

 chloriosulfurin consisted of a mixture of xanthophyll and carotene, and zoofulvin 

 of almost pure xanthophyll. Further investigations in this field have been carried 

 out by KuHN and Brockmann^^ and by Capper, McKibbin and Prentice^^. 

 With two exceptions {phasianus colchicus, "Rosen" and Anser domesticus) , 

 all these investigations are of a purely qualitative nature. 



(iii) Carotenoids from blood serum and inner organs 



It has long been known that a lipochrome pigment is present in the blood 

 serum of pigeons and chicken. It was later identified by spectroscopic means 

 as xanthophyll by Schunck^. The same pigment has been found in the livers 

 of chicken^^. It appears that the carotene and cryptoxanthin contained in the 

 diet (maize) are quickly degraded, while xanthophyll, which has no vitamin A 

 activity, is stored. 



(iv) Carotenoids from egg yolk 



The pigments from egg yolk have long aroused the interest of chemists. 

 Stadeler^" was the first to isolate a crystalline pigment with well-defined 

 properties from chicken egg yolk. Thudichum^^ classified this pigment as one 

 of the "luteins" (lipochromes) and it was related to xanthophyll by Schunck^^. 

 In 1912, Willstatter and Escher^^ proved the xanthophyll nature of the 

 pigment isolated by Stadeler and in 1931 Kuhn and co-workers showed it to 

 be a mixture of xanthophyll and zeaxanthin^*. The composition of the egg 

 yolk pigments can be altered by varying the diet^". Carotene has also been shown 

 to be present in chicken egg yolk^^. 



TABLE 25 (References see p. 99-107) 



CAROTENOIDS IN BIRDS* 



Acanthis flammea (red forehead)^'*: Anser dornesticus [retma)'^'^^: Kst?LcenQ, 



Astacene(?), carotenoids. astaxanthin^''®. 



Anipelis garrula^''*: Astacene(?), Anas penelope (foot skin)'''*. 



carotenoids. A nas platyrhyncha (red foot skin, beak 



* Tbe above table is taken from O. Walker, Dissertation, Zurich, 1935. 

 References p. 108. 



