DEFINITIONS AND NOMENCLATURE 



It is recommended that newly discovered carotenes of unknown 

 structure be named by using the term " carotene " prefixed by Greek 

 letters or terms appropriate to the source or properties of the carotenes, 

 e.g.y " co-carotene,'^ or '* lycocaroteneJ" A mixture of a- and p-carotenes 

 in which the p-isomer predominates (about 90-95 per cent, of the total) 

 has been used by many workers without further purification ; in this 

 work such a mixture will be termed " carotene.'' 



New^ xanthophylls are to be named by using the term " xanthin " to 

 which a prefix appropriate to its source is added. As structures of these 

 pigments become known, they can be described in terms of the parent 

 hydrocarbon, using the rules of nomenclature set out in this chapter ; 

 e.g.y zeaxanthin (not zeaxanthol) becomes either 3 : 3' -dihydroxy- 

 p-carotene or p-carotene-3 : 3' -diol. The author does not feel that 

 the chemical names should oust well-established trivial names in most 

 biochemical discussions ; in fact, it will be found that in the following 

 pages chemical names of carotenoids of known structure are given 

 together wdth the trivial names only when they are first mentioned ; 

 thereafter the trivial names are used. Dyson ^^ has applied his method 

 of enumeration to the carotenoids. 



Up to now the formulae of the carotenoids discussed have been 

 given in full ; in the chapters which follow, unless there are good 

 reasons not to do so, the formulae wdll be reproduced in a ** shorthand " 

 version, demonstrated in the following example : — 



REFERENCES 



1. Berzelius, J. J. (1837), Liebigs Ann., 21, 257. 



2. Fr£my, E. (1860), C. r. Acad. Sci., Paris, 50, 405. 



3. Stokes, G. G. (1864), J. Chem. Soc, 17, 304. 



4. GuiBOURT, N. J., ROBINET, S., and Derheims, J. (1827), y. pharm. chim., 13, 26. 



5. TSWETT, M. (1911), Ber, deutsch. botan. Ges., 29, 630. 



6. Karrer, p. (1948), Bull. Soc. Chim. Biol., 30, 150. 



7. Chem. Eng. News (1946), 24, 1235. 



8. Karrer, P. et al. (1929), (1930), Helv. Chim. Acta., 12, 790 ; 13. 1063. 



9. KUHN, R., WiNTERSTEiN, A., and Lederer, E. X1931), Hoppe-Seyl. Z., 197, 141. 



10. Karrer, P., Solmssen, U., and Gugelmann, W. (1937), Helv. Chim. Acta., 20, 1020. 



11. Dyson, G. M. (1947), Chem. Eng. News, 25, 1766. 



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