78 CAROTINOIDS AND RELATED PIGMENTS 



carotin, but whether other carotinoids are present has not been de- 

 termined. 



Ampelopsis hederacece. Hansen (1884) classified the pigment of 

 the fruit as a lipochrome and Kohl (1902) obtained carotinoid crys- 

 tals by the Molisch microchemical method. 



Aglaonema commutatum Shott. Tammes (1900) obtained positive 

 carotinoid color tests on the chromoplastids of the fruit. Van Wissel- 

 ingh (1915) made a detailed study of the microchemical crystals 

 obtained by the Molisch method and concluded that the chief pigment 

 is lycopin, but that other carotinoids are present also. 



Citrus limonum (Lemon). Neither Kohl (1902) nor Tschirch (1904) 

 could find evidence of carotinoids being involved in any way in the 

 pigmentation of the yellow skin of this fruit. 



Cucumis citrullis (Watermelon). A. and G. de Negri (1879) first 

 isolated the pigment of the flesh of this fruit and called it rubidin 

 because of its red color. Red, needle shaped crystals were described, 

 soluble in ether, benzine and chloroform, forming yellow or yellow- 

 red solutions, and in carbon disulfide forming a magnificent rose- 

 colored solution. The insolubility of the crystals in alcohols and the 

 characteristic three-banded absorption spectrum which was found to 

 be identical with that of the red tomato pigment obviously classifies 

 the pigment as a carotin if not as lycopin itself, as there is good reason 

 to believe. Courchet (1888) also crystallized the watermelon pig- 

 ment and found that the crystals resembled completely in form and 

 in color those obtained from the tomato. Monteverde and Lubimenko 

 (1913b) have definitely confirmed its identity with lycopin, as well 

 as to show that carotin and xanthophyll are also present in the red 

 fruit pulp. 



Cucurbito pepo L. (Pumpkin). Arnaud (1885) stated that he ob- 

 tained crystals of pigment from the flesh of this fruit which were iden- 

 tical in properties with carrot carotin. Schrotter-Kristelli (1895b) 

 later made a closer study of the pigment of this family of plants, 

 using for the source of his material the thin deep-red outer layer of 

 the pericarp of so-called Turk's-cap gourd. The pigment was not 

 found to be readily extractable by alcohol, even by hot absolute alco- 

 hol, but was readily soluble in petroleum ether, ether, chloroform and 

 carbon disulfide. The recrystallized pigment was found to be iden- 

 tical in solubility and in its reactions with carotin, especially the 

 emerald green color on addition of HC1 to the alcoholic solution of 

 the pigment. The conclusion seems justified that carotin is the chief 



