2 CAROTENOIDS CONTAINING HYDROXYL GROUPS XI 



Chemical Constitution 



C CHj CHo 



CH2 C=^CH CH3 CH3 CH3 CH3 C 



I A I I I I I I 



HOCH C CH— C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CH CHj 



H3C-C CHOH 

 Chrysanthemaxanthin ^ / 



CH 



Chrysanthemaxanthin has the same empirical formula as flavoxanthin^^^. 

 It is identical with the latter in many respects, with the exception of the melting 

 point, the reaction with concentrated aqueous hydrochloric acid and the 

 strength of adsorption on zinc carbonate. On the basis of these facts and its 

 mode of formation together with flavoxanthin by the action of dilute acids on 

 xanthophyll epoxide, Karrer and Jucker^*^ assigned the above formula to 

 chrysanthemaxanthin. The formula is in complete accord with all the properties 

 of the pigment. 



The isomerism of flavoxanthin and chrysanthemaxanthin is presumably 

 steric in origin. Structural isomerism is unlikely as the two pigments have 

 identical absorption spectra. The isomerism may be due to the fact that the 

 hydroxyl and ether groups in ring A are in czs-positions in one pigment and in 

 ^raws-positions in the other. The question of this isomerism requires further 

 investigation. 



Properties and Physical Constants 



Crystalline form: Chrysanthemaxanthin crystallises from a mixture of 

 benzene and methanol in golden yellow leaflets. 



Melting point: 184-185° (uncorr., evacuated capillary). 



Solubility: Chrysanthemaxanthin exhibits the same solubilities as flavo- 

 xanthin. It is readily soluble in chloroform, benzene, acetone and ether, a little 

 more sparingly in ethanol and methanol, and almost insoluble in petroleum 

 ether. 



Spectral properties: 



Solvent Absorption maxima 



Carbon disulphide 479 449 m// 



Chloroform 459 430 m^ 



Petroleum ether 450 421 m/i 



Ethanol 448 421 m/^ 



References p. 214-21'j. 



