240 CAROTENOIDS CONTAINING CARBONYL GROUPS XII 



found in the lower layer. The absorption maxima are located at slightly shorter 

 wavelengths than those of the parent pigment. 



Astaxanthin dicaprylate CjgH-oOg^*: 



This ester is prepared by the treatment of astaxanthin in pyridine with 

 caprylic acid chloride. It can be purified by chromatography on calcium car- 

 bonate from petroleum ether solution. Ast^anthin dicaprylate crystallises 

 from a mixture of petrol and ethanol in dark red crystals, m.p. 121-124° (not 

 sharp, Berl-block, in vacuum). In the partition test with 90% methanol and 

 petroleum ether, the ester is found almost quantitatively in the upper layer. 

 The ester becomes hypophasic only on employing 97% methanol. 



AstaxantJiin dipalmitate C-^HugOg^® : 



This ester is prepared by a procedure analogous to that described for 

 astaxanthin dicaprylate. It crystallises from a mixture of pyridine, methanol 

 and water in flat, violet-red needles, m.p. 71.5-72.5°. Astaxanthin dipalmitate 

 exhibits purely epiphasic behaviour. 



Astaxanthin monopalmitatc C5gH8205^' : 



This derivative 'is obtained by the esterification of astaxanthin with the 

 calculated amount of palmitic acid chloride. The ester crystallises from a 

 mixture of benzene and methanol in red spheres, m.p. 113.5-114.5° (corr.). 

 Astaxanthin monopalmitatc is entirely epiphasic on partition between 90% 

 methanol and petroleum ether. 



Astaxanthin esters from Haematococcus pluvialis. 



From Haematococcus pluvialis, Kuhn and Sorensen^^ isolated various 

 esters of astaxanthin, the composition of which has not yet been definitely 

 determined. 



Ovoverdin and Chromoproteids. 



The probable structure of ovoverdin has been described above (p. 236). 

 It is very probable that the nature of thceprotein component is different in 

 different organisms. A common characteristic of all these chromoproteids is 

 their green or blue colour, water solubility, and great sensitivity towards heat, 

 acids and organic solvents (with the exception of petroleum ether) . The protein 

 of the chromoproteids is coagulated by these reagents, leaving the free pigment 

 component, astaxanthin. 



6. CAPSANTHIN C40H58O3 



History 



1817 Braconnot carries out the first investigations on the pigments of paprika^^. 

 1869 Thudichum recognises the close relationship of the paprika pigments to 

 the carotenoids^", a relationship later confirmed by Pabst^^ and Kohl^^. 

 References p. 253-255. 



