3 CRYPYOXANTHIN i-j-j 



is the most probable. By oxidation with chromic acid, Kuhn and Grundmann 

 obtained 4.85 mols of acetic acid. 



The formula for cryptoxanthin is in agreement with the fact that this 

 phytoxanthin possesses vitamin A activity^- ^°' ^^. 



Properties 



Crystalline form: Cryptoxanthin crystallises from a mixture of benzene and 

 methanol in lustrous prisms which tenaciously retain some methanol. 



Melting point: 169° (corr., evacuated capillary). 



Solubility: As would be expected from its constitution, cryptoxanthin has 

 properties intermediate between those of /^-carotene and zeaxanthin. The 

 pigment is easily soluble in chloroform, benzene and pyridine, and less soluble 

 in ligroin, petroleum ether, methanol and ethanol. 



Spectral properties: 



Solvent: Absorption maxima: 



Carbon disulphide 519 483 452 m/x 



Chloroform 497 463 433 m/z 



Ethanol, absolute 486 452 424 m/^i 



Petrol 485.5 452 424 mpi 



Hexane 484 451 423 ra/t 



Optical activity: Cryptoxanthin exhibits no optical acti\'ity. 



Partition test: On partition between petroleum ether and 90 % methanol, 

 cryptoxanthin is found in the upper layer, and thus behaves like a hydrocarbon. 

 With 95 % methanol, however, it is hypophasic. 



Chromatographic behaviour: Cryptoxanthin is more strongly adsorbed on 

 calcium hydroxide than the carotenes and can readily be separated from the 

 latter in this way. On zinc carbonate or calcium carbonate, it is held less strongly 

 than phytoxanthins with two hydroxyl groups. The separation of crypto- 

 xanthin from rubixanthin presents some difficulty. 



Colour reactions: Cryptoxanthin gives a dark blue colouration with anti- 

 mony trichloride in chloroform solution. The solution exhibits a maximum at 

 590 m/x (cf. /5-carotene) . 



Detection and estimation: The separation of cryptoxanthin from other 

 carotenoids is achieved by means of chromatographic adsorption. The pigment 

 can be identified by the determination of absorption maxima and by means of 

 the partition test. For the colourimetric estimation, a standard solution of 

 azobenzene in ethanol can be used^^. 



Physiological properties: Cryptoxanthin exhibits vitamin A activity (cf. p. 14). 

 References p. 214.— 21J. 

 Carotenoids 12 



