3i6 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



properties of an enol, the grouping =C.(OH) can be excluded. On ozonisation, 

 Le Rosen and Zechmeister obtained 0.55 mols of acetone per mol of 

 pigment (after substr action of the blank) thus indicating the presence of an 

 isopropylidene grouping. Finally, the long-wavelength location of the ab- 

 sorption maxima indicates the presence of 13 conjugated bonds. The position 

 of the hydroxyl group is not certain ; for reason of analogy it is assumed to be at 

 carbon atom 3'. 



The experimental results are in agreement with the proposed formula for 

 celaxanthin, but do not exclude the possibility of other structures. 



Properties 



Crystalline form: Celaxanthin crystallises from petroleum ether and ethanol 

 in long needles which are combined in rosettes or clusters. In bulk, the pigment 

 has the appearence of a dark red crystalline powder, somewhat reminiscent of 

 lycopene. 



Melting point: 209-210° (corr., Berl-Block, capillary filled with carbon 

 dioxide). Another sample of the pigment had m.p. 204-205°. 



Solubility: Celaxanthin is sparingly soluble in carbon disulphide and 

 benzene at room temperature. It is slightly soluble in petroleum ether and almost 

 insoluble in methanol and ethanol. 



Partition test: On partition between petroleum ether and 85 % methanol, 

 the pigment is entirely epiphasic. With 95 % methanol the lower layer is also 

 coloured. 



Optical activity: The optical activity could not be determined because of the 

 high colour intensity. 



Spectral properties: 



Solvent Absorption maxima 



Carbon disulphide . . 562 521 487 455 xxxfi 



Ethanol 520.5 488 455 m/z 



Petroleum ether . . . 520 486.5 456 (429)m^i 



Chromatographic behaviour: Celaxanthin is well adsorbed on calcium 

 hydroxide from petroleum ether or from a mixture of petroleum ether and 

 acetone. Benzene, or a mixture of benzene and acetone can also be used as 

 solvents for this adsorbent. The pigment can be eluted with the same solvents, 

 but containing a little methanol. 



Cis-trans Isomers 



Le Rosen and Zechmeister found that celaxanthin isreversibly isomerised 

 on warming in the same way as torulin (cf. p. 329). Le Rosen and Zechmeister 

 References p. 341-343. 



