TO FLAVOXANTHIN 207 



Solvent Absorption ynaxima 



Carbon disulphide 501.5 472 m^ 



Benzene 482 453 m^ 



Petroleum ether ,47 1..- — ^442 m/z 



Ethanol 473 445 m// 



On treating xanthophyll epoxide with acetic anhydride in pyridine, xantho- 

 phyll epoxide diacetate is obtained. This compound exhibits entirely epiphasic 

 behaviour. M.p. 184-185° (uncorr., evacuated capillary) . 



Xanthophyll epoxide has approximately the same solubility in organic 

 solvents as xanthophj-ll. It shows entirety hypophasic properties in the partition 

 test. On treating an ethereal solution with concentrated aqueous hydrochloric 

 acid, the latter assumes a blue colour. 



Xanthophyll epoxide is extremely unstable towards acids. Even traces of 

 hydrochloric acid, such as occur, for instance, in chloroform which has been 

 stored for some time, convert the pigment into the two isomeric furanoid 

 oxides, flavoxanthin and chrysanthemaxanthin. These pigments are described 

 below (p. 207, 211). 



Eloxanthin (Xanthophyll epoxide) 



During an investigation of the carotenoids from the leaves of elodea cana- 

 densis, Hey^^^ discovered a previously unknown pigment for which he proposed 

 the term eloxanthin. The properties of eloxanthin are so similar to those of 

 xanthophyll epoxide, that the identity of the two pigments appeared very 

 probable. Karrer and Rutschmann^^"^ were in fact able to show the presence 

 of xanthophyll epoxide in elodea canadensis and as no second pigment showing 

 the properties of eloxanthin was present, the identity of the two compounds 

 is very probable. 



Natural xanthophyll epoxide (eloxanthin) is optically active, [p.Yc\ ^ 

 +225° in benzene. The optical activity of the partially synthetic product has 

 not yet been determined. 



10. FLAVOXANTHIN C^oHggOg 



History 



1932 KuHN and Brockmann^^^ isolate flavoxanthin from blossoms of Ranun- 

 culus acer. 



1942 Karrer and Rutschmann^^^ report the occurrence of this phytoxanthin 

 in other plants and propose a provisional formula. 



1945 Karrer and Jucker^*" carry out a partial synthesis of flavoxanthin 

 which establishes the constitution of the pigment with a high degree of 

 certainty. 



References p. 214— 21 j. 



