542 VI. CAROTENOIDS AND RELATED COMPOUNDS 



of the corresponding nW-tmns forms. Another neo-7-carotene, namely, 

 neo-7-carotene P, has been reported in the firethorn (Pyracantha angusti- 

 folia Schneid.).'''' It probably differs from the neo-7-earotene in water- 

 melon {Citnillus vulgnris Schrad.) reported earlier by Zechmeister and 

 Polgar.^^^ Although 7-carotene or its isomers have been found in many 

 types of plants, there are only two instances in which it has been noted in an 

 animal form. Thus, Lederer^*^^ isolated the pigment from the skin of the 

 small green water tortoise (Chrysemys elegans), and Dmmm and O'Connor^"^ 

 were able to separate it in crystalline form from the red rock-sponge 

 {Hymeniacidon sanguineum Grant). 



(4) Other Carotenes 



In addition to a, j3, and 7-carotene, several other members of this group 

 have been reported, but their structure has not been exactly defined. 

 These include 5-carotene, the presence of which in the bark of the Gono- 

 caryum pyriforme was originally described by Winterstein." Strain^-^ later 

 reported 5-carotene in carrots, but later renamed the pigment i'-carotene^"^ 

 and indicated that it was characterized by absorption spectra at 400 and 

 425 mjix and by the absence of absorption in the region of 450 m/x. White 

 et al.^^'^ confirmed the earlier work of Strain. More recently, Nash and 

 Zscheile^^^ separated ^-carotene from special tomato strains and carrots. 

 These authors also state that f-carotene is present in butter, as well as in 

 yellow beef fat and eggs. f-Carotene has been found to be inactive as a 

 precursor of vitamin A.^^^ The empirical formula is believed to be C40H64, 

 and its most probable structure is 5,f),7,8,5',G',7',8'-octahydrolycopene.^'^ 

 Like lycopene, the chain is open at both ends. 



(5) Lycopene 



Lycopene is one of the carotenoids which has been known for a long 

 time. As early as 1873, Hartsen^^"* isolated a dark red, crystalline pigment 

 from the red berries of Tamus communis (black bryony) which was probably 

 lycopene. It was also prepared in a somewhat impure state several years 



207 E. Lederer, Bull soc. chim. bioL, 20, 554-566 (1938). 



208 P. J. Drumm and W. F. O'Connor, Nature, U5, 425 (1940). 



209 H. H. Strain and W. M. Manning, J. Am. Chem. Soc, 65, 2258-2259 (1948). 



210 J. W. White, F. P. Zscheile, and A. M. Brunson, /. Am. Chem. Soc, 64, 2603-2606 

 (1942). 



211 H. A. Nash and F. P. Zscheile, Arch. Biochem., 7, 305-311 (1945). 



2'2 J. W. Porter, H. A. Nash, F. P. Zscheile, and F. W. Quackenbush, Arch. Biochem., 

 10, 261-265 (1946). 



213 H. A. Nash, F. W. Quackenbush, and F. P. Zscheile, J. Am. Chem. Soc, 70, 3613- 

 3615 (1948). 



214 Hartsen, Compt. rend., 76, 385 (1873); Chem. Zentr., 1873, 204. Cited by P. Karrer 

 and E, Jucker, Carotinoide, Birkhauser, Basle, 1948, p. 113. 



