15^ Plant Pigments [March, 



xanthophyll is 0.07 to 0.12 percent and Carotin 0.03 to 0.08 percent, 

 or about i molecule of Carotin to 1.5 to 2 molecules of xanthophyll. 



Xanthophyll has the formula, C40H56O2, and thus may be con- 

 sidered an oxid of Carotin. Nothing is known of the function of 

 the oxygen atoms ; they are considered ether-like, since xanthophyll 

 does not give a reaction f or ^ COH, = CO or — COOH. It 

 appears to give a very easily dissociable addition product when an 

 ether Solution is treated with methyl alcoholic potash. It shows a 

 tendency to crystallize with alcohol of crystallization and is best 

 obtained solvent-free by precipitation from Chloroform with petrol- 

 eum ether. The typical crystal forms are long tables and prisms. 

 which are pleochroic and often show a steel blue luster. In trans- 

 mitted light they are yellow, and are red only where several crystals 

 Gross. This distinguishes them from Carotin, for the colors of the 

 Solutions are very similar. It melts at 172°. Xanthophyll is rela- 

 tively Stahle towards oxygen in dilute sol., but the pulverized sub- 

 stance takes up 36.5 percent of its weight of oxygen, giving a Com- 

 pound, which, precipitated from methyl alcohol by ether, has the 

 formula, C4oH560i8- Like Carotin, it gives a di-iodid, tufts of thin, 

 dark violet, prisms with metallic luster. It is easily decomposed. 

 The bromid, C4oH4oBr22, is also similar to that of Carotin, It gives 

 the same color reactions with conc. sulfuric acid and alcoholic hydro- 

 chloric acid sol. 



Lutein.^^ As mentioned above, a Compound isomeric with 

 xanthophyll has been found in lutein, the coloring matter of egg- 

 yolk. This was first isolated in a pure State by Willstätter and 

 Escher,^^ who obtained 4 gm. of very crude pigment from 6000 eggs 

 (iio k.). The yolks were coagulated with alcohol (7 1. to 6 k. of 

 eggs) and the coagulum extracted with acetone (5.4 k. were shaken 

 with 3 1. of acetone and filtered; 2.8 k. of the residue were shaken 

 with 2 1. of acetone for one hour and then washed on a filter with 

 2 1. of acetone). Phosphatids were removed by shaking the acetone 

 with petroleum ether, washing with water, and mixing the petroleum- 

 ether sirup with two vol. of acetone; the acetone was then removed 

 by washing with water, the petroleum ether concentrated to about 

 2 1., filtered from cholesterol, diluted to about 6 1. and cooled. 



31 Although lutein is an animal pigment, its dose relationship to xanthophyll 

 Warrants its inclusion here. 



32 Willstätter and Escher: Ztschr. f. physiol Chem., 76, 214, 1911-1912. 



