CAROTINOIDS AND RELATED 



PIGMENTS 



Chapter I 



General Distribution of Carotinoids. The Pigments 



Defined 



Red, orange and yellow pigments which can be extracted from tis- 

 sues by fat solvents are found abundantly in all forms of living mat- 

 ter. In the plant world they are present in nearly all species ranging 

 from bacteria, the lowest forms of cryptogams, to the dicotyledons, 

 the highest forms of phanerogams. Similarly in the animal kingdom 

 we find yellow to reddish pigments in all forms of both invertebrates 

 and vertebrates, from protozoa to man. The earliest workers in both 

 the plant and animal fields naturally based the classification of the 

 pigments on simple properties, so that it is not surprising to find that 

 many names have been proposed for what is obviously the same 

 pigment. 



This diversity in nomenclature is found to be especially true among 

 the yellow animal pigments, and can be traced in most instances to 

 slight variations in certain of the simple properties which were re- 

 garded as specific for various types of pigment. In some cases these 

 variations were due to the fact that the method employed for the iso- 

 lation of the pigment did not insure its freedom from other pigments of 

 similar but not identical properties. In other cases the variations were 

 due to the examination of the pigment in amorphous condition or in 

 solution, without reference to the possible effect which these states 

 might exert upon the particular properties being studied. Again, there 

 was frequently an abundant contamination with lipoid impurities, 

 which are invariably separated with the pigments from animal tis- 

 sues. Another, still more important cause for these variations was 

 the failure to protect the pigments from oxidation. The true caro- 

 tinoids, which unquestionably comprise the great majority of yellow 



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