88 CAROTINOIDS AND RELATED PIGMENTS 



ties of this pigment have not yet been explained and the work should 

 be repeated. 



Monnier-Williams (1912) has shown that carotin is one, if not the 

 chief pigment of unbleached wheat flour. The author has confirmed 

 the presence of both carotin and xanthophylls in the wheat grain 

 (Triticum vulgare). Carotinoids are also present in small amounts in 

 barley (Hordeum satiuum) and oat (Avena sativa) grains, as shown 

 by Palmer and Kempster (1919c) and even in traces in the grains of 

 polished rice (Oryza satira) , as shown by the experiments of the same 

 authors (1919a). 



Summary 



Carotin, the specific pigment of the carrot root, was first isolated 

 and named by "\Yaclu-nroder (1826). The hydrocarbon nature of the 

 pigment was discovered by Zeise (1847) and confirmed by Arnaud 

 (1886). The formula C 40 H 50 was established for the pigment by 

 Willstiitter and Mieg (1907) and confirmed by Euler and Nordenson 

 (1908) and others. Euler and Nordenson showed that xanthophylls 

 are also present in carrots, a fact confirmed by Palmer and Eckles 

 (1914g). Escher (1909) was unable to determine the constitution of 

 carrot carotin although he had at his disposal 150 grams of pure 



pigment. 



Other yellow roots, such as parsnip, sweet potato, yellow turnip, 

 rutabaga, squash, etc., undoubtedly contain carotinoids but the exact 

 nature of the pigments has not been determined. 



The existence of yellow pigments in chloroplastids was discovered 

 by Fremy (I860), but the first definite separation from green pig- 

 ment was made by Stokes (1864), and later by Kraus (1872) and 

 Sorby (1873) and others. 



The first crystals of yellow plastid pigment were observed by Fremy 

 (1865) and later by Hartsen (1873a), Bougarel (1877), Borodin 

 (1883) and Guignet (1885). It remained for Arnaud (1885), how- 

 ever, to observe the identity of these crystals with carrot carotin, 

 which was confirmed by chemical analysis through the work of Im- 

 mendorff (1889) and Willstiitter and Mieg (1907). 



The plurality of the yellow chloroplastid pigments was first sug- 

 gested by Stokes (1864a) and definitely demonstrated by Borodin 

 (1883). The correct procedure for the separations of these pigments 

 as well as their present classification as carotinoids was developed by 

 Tswett (1906 to 1911) on the basis of the observations of Kraus 



