30 TROLLIXANTHIN 335 



29. OSCILLAXANTHIN 



In the course of an investigation of the carotenoids of Oscillatoria rubescens, 

 Karrer and Rutschmann^^ found, besides myxoxanthin, myxoxanthophyll, 

 zeaxanthin* and )3-carotene, a hitherto unknown pigment for which they 

 proposed the term oscillaxanthin. 



For the isolation of this pigment, the algae are dehydrated with ethanol, dried 

 and extracted with warm methanol. This extract is combined with that obtained 

 from the dehydration and the solutions are strongly concentrated. They are then 

 saponified with aqueous potassium hydroxide and extracted with a large volume of 

 ether, and the aqueous phase is almost neutralised with dilute sulphuric acid. From 

 this solution the methanol is removed by distillation and the remaining aqueous 

 solution is slightly acidified with dilute sulphuric acid (to pH4-5). The solution is 

 then again extracted with ether whereby most of the saponification products of 

 chlorophyll are removed. From the mother liquors, oscillaxanthin can then be 

 extracted with ethyl acetate. After evaporation of the solvent the pigment is taken 

 up in acetone and chromatographed on zinc carbonate. After elution, the oscilla- 

 xanthin is further purified by precipitation from ethyl acetate by means of ether. 

 The pigment could not be obtained in a pure state because of the small amount of 

 material available. 



Oscillaxanthin exhibits acidic properties. It is readily soluble in alcohol, 

 pyridine and acetone, but almost insoluble in ether, benzene, carbon disulphide 

 and petroleum ether. Oscillaxanthin esters are readily soluble in ether, benzene, 

 pyridine and chloroform, but almost insoluble in ethanol. The constitution of 

 oscillaxanthin is still entirely unknown. 



Solvent: Absorption maxima: 



Carbon disulphide 568 528 494 m^** 



Methanol 531 496 464 m/t 



Pyridine 552 514 483 m/< 



Antimony trichloride produces a blue-green, concentrated sulphuric acid a 

 blue, and concentrated hydrochloric acid an unstable blue colouration. 



30. TROLLIXANTHIN AND TROLLICHROME C4oH5g04 



During investigations of the carotenoids of Trollius europaeus, Karrer and 

 JucKER^^ discovered a new pigment which had previously escaped notice and 

 for which they proposed the name trollixanthin^'^. It posseses the properties of 

 an epoxide. In addition to trollixanthin, the flowers also contained jS-carotene, 



I. M. Heilbron and B. Lythgoe, /. Chem. Soc. 1936, 1376 found myxoxanthin, 

 myxoxanthophyll, ;3-carotene and xanthophyll, but no zeaxanthin in Oscillatoria rubescens. 



Absorption maxima in carbon disulphide refer to solutions prepared by diluting one 

 drop of an alcoholic solution of the pigment with a large volume of carbon disulphide. 



References p. 341-343. 



