82 CAROTINOIDS AND RELATED PIGMENTS 



crystallized them by the Molisch method. According to Lubimenko 

 (1914a) lycopin is the chief pigment present. Van Wisselingh (1915) 

 obtained crystals of pigment by the acid microchemical method as well 

 as by the alkali method, and on further study concluded that lycopin 

 is the chief pigment, but that another orange-red carotinoid is present 

 also, which fails to react towards the I,-KI reagent. A further study 

 of the latter pigment, which van Wisselingh found in other fruits also, 

 would seem to be desirable. It has previously been considered that 

 the frequent failure of the iodine reaction was characteristic of the 

 animal lipochromes only, and was, in fact, one point of difference 

 between the plant and animal lipochromes. This differentiation seems 

 to break down in the light of van Wisselingh's results. 



Capsicum annum (Red Pepper). The red pepper pigment has 

 interested a number of plant biologists. Thudichum (1869) first 

 classed it with the luteins. Pabst (1892) was unable to identify it 

 spectroscopically with carotin. Kohl (1902) regarded the pigment as 

 completely identical with carotin, but in this he was mistaken, for 

 Tschirch (1904) recognized the close relation of the pepper pigment 

 spectrum with that of lycopin. Duggar's (1913) spectroscopic obser- 

 vations led him to conclude that lycopersicin (lycopin) is the pigment 

 of both the skin and flesh of the red pepper. While van Wisselingh 

 (1915) obtained a positive carotinoid test using the alkali crystalliza- 

 tion method, he does not classify the Capsicum fruit among those con- 

 taining lycopin. It should be stated that the measurements of the 

 absorption bands of lycopin, given by Tschirch (1904), do not cor- 

 respond exactly with the lycopin bands (in the same solvent) given 

 by Willstatter and Escher (1910). Monteverde and Lubimenko 

 (1913b) found the red pepper pigment to be spectroscopically identi- 

 cal with lycopin but because of the ease of solubility of the crude 

 pigment in alcohol, in opposition to the usual difficult solubility of 

 lycopin in this solvent, they have named it lycopin B. 



Lycopersicum esculentum (Tomato). The red tomato pigment has 

 been by far the most extensively studied of the fruit pigments of the 

 carotinoid class, and is the only one, in fact, for which we possess at 

 present definite chemical knowledge that it is not identical with the 

 usual carotin and xanthophylls of the chloroplastids. 



Millardet (1876), who first investigated the tomato pigment, recog- 

 nized that it is not identical with the orange and yellow pigments 

 which characterize other fruits. He therefore proposed the name 

 solanorubin for the pigment. It is recognized now that the name was 



