22 CAROTINOIDS AND RELATED PIGMENTS 



annatto, which is widely used for the artificial coloring of butter and 

 cheese, and which' has been commonly regarded as a lipochrome and 

 was included by Thudichum among the luteins. The annatto pig- 

 ment does, in fact, correspond in almost every particular with the 

 class characteristics of the lipochromes. It is not entirely unattacked 

 by alkalies, however, and furthermore is decomposable into a number 

 of well known substances, such as m-xylene, m-ethyl toluene, and even 

 palmitic acid. It reduces Fehling's solution even in the cold. Its 

 constitution is unknown, as yet, but its elementary composition cor- 

 responds to the formula C 28 H 34 5 , according to Etti (1878), or 

 C 29 H 34 5 , according to van Hasselt (1909). It is thus seen that 

 bixin, while corresponding well to the lipochrome classification, is in 

 no sense a carotinoid. Palmer and Kempster (1919c) have shown that 

 the annatto pigment has no effect on the coloration of the tissues 

 when fed to fowls. 



Other vegetable coloring matters of a yellow color giving reactions 

 in some cases similar to carotinoids, but of entirely different com- 

 position, are Crocin, and Crocitin, flavones which are found in the 

 petals and pollen grains of the Indian crocus (Crocus sativus), which 

 dissolve in concentrated sulphuric and nitric acids, with a deep blue 

 color, which passes, however, into a brown shade. Another yellow 

 vegetable dye showing a like reaction, although the after shade with 

 the acid reagents is yellow, is the nyctanthin which Hill and Sikar 

 (1907) described a few years ago. The empirical formula for this dye 

 C 20 H 27 4 , has an interesting resemblance to that of the carotinoids, 

 at least when one doubles the above formula. 



The yellow, orange, and red colors seen frequently among the fungi 

 of the lichen and mushroom types appear to be due in many cases to 

 pigments of a nature quite different from the carotinoids. Chryso- 

 phanic acid, mentioned above, sometimes occurs among these plants, 

 as well as many other like coloring matters which have been named 

 of Zopf (1889b, 1892b, 1893b) and which other workers have found 

 occurring among the Basidiomycetes. In color and in some of their 

 solubility properties these pigments resemble the carotinoids, and cer- 

 tain of them give a color reaction with concentrated sulphuric acid 

 which is not unlike that regarded as characteristic of the lipochromes. 



Non-carotinoid Animal Pigments 



Several yellow pigments are present in animal tissues and fluids 

 which are not to be mistaken for carotinoids. One of these, whose 



