0. ISLER Chemical Research Department, F. Hoffmann-LaRoche&Co. Ltd.,
Basle, Switzerland A. General Remarks . . . 12 B. Historical Development
13 C. Scope and Limitations 15 D. Vitamins A and Provitamins A . 15 E.
Carotenoids as Natural Colouring Matters . 19 F. Other Natural Pigments
and Related Compounds. 21 G. Nomenclature . . . 22 H. Lists of
Carotenoids 24 I. Acknowledgments 25 References . . . . . . 25 0. ISLER
12 A. General Remarks The brightly coloured carotenoid pigments have
aroused the curiosity of scientists since the beginning of organic
chemistry. Indeed some of the oldest studies were published during the
early 19th century. Research on carotenoids can be separated into four
broad periods according to the selection of problems and the methods of
attacking them. During the 19th century, the emphasis was on isolation
of the pigments and their characterization by measurements of light
absorption. The second period (1900-1927) centred on the determination
of empirical formulae and on tentative efforts to discover a role in
photosynthesis. The third period (1928-1949) was dominated by the
provitamin A concept, by establishing structural formulae and developing
synthetic methods. The latest period (1950 to the present) has seen an
expo nential increase in the number of known carotenoids accompanied by
notable advances in total synthesis and in the determination of absolute
configura tions. The recent explosive growth in knowledge has in no
small part been due to new separation methods (e. g."