PREFACE 



The carotenoids are not only amongst the most widespread of the 

 naturally occurring groups of pigments, but probably also have the 

 most varied functions ; witness their known roles in photokinetic 

 responses of plants, in phototropic responses of fish and as vitamin A 

 precursors in mammals and birds. Pigments with such wide dis- 

 tribution and such diverse functions are obviously of great interest to 

 biological scientists with very different specializations, especially as it 

 is unlikely that the study of the functions of carotenoids is anywhere 

 near complete. 



The primary aim of the present work is to discuss the distribution, 

 biogenesis and function of the carotenoids throughout the plant and 

 animal kingdoms in such a way that, because of, rather than in spite of 

 its biochemical bias, it will be of value to workers interested in all the 

 biological aspects of these pigments. The biochemical approach is 

 considered the most effective because, generally speaking, most progress 

 in the study of carotenoids in living material has been achieved using 

 biochemical techniques, be they applied by zoologists, botanists, 

 entomologists, microbiologists or other specialists ; what is even more 

 important is that a consideration of the present position makes it certain 

 that further fundamental progress will also only be made along bio- 

 chemical lines. 



Although many good accounts of the pure chemistry of the caro- 

 tenoids are available, the most recent and comprehensive being Karrer 

 and Jucker's Carotinoide (Birkhauser, Basel, 1948), (now available in an 

 English translation by E. A. Braude and published by Elsevier) 

 sufficient descriptive chemistry has been included to make this book 

 adequately self-contained and to allow the discussion to be followed 

 without undue difficulty. The most up-to-date spectrographic data 

 have also been included, because spectrophotometric techniques are of 

 great importance in identifying carotenoids in biological systems. 



The first comprehensive survey of the biochemistry of carotenoids 

 was made in 1922 by the late L. S. Palmer (Carotinoids and Related 

 Pigments y Chemical Catalog Co., New York) ; this was followed in 1934 

 by Zechmeister's Carotinoide (Springer, Berlin) and Lederer's Les 

 Carotenoides des Plantes (Hermann, Paris), and in 1935 by Lederer's 

 Les Carotenoides des Animaux (Hermann, Paris). Since then a survey 

 such as the present one has not appeared. In order to present a full 

 picture, much of the pre-1934 work has been reconsidered and, as far 



