324 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



absorption maxima indicates that the 12 double bonds are in conjugation. 

 Eschscholtzxanthin is extremely unstable in air. The rate of oxygen uptake 

 is different in different organic solvents and is not increased by haemin, in 

 contrast to the behaviour of lycopene^*. If solutions of eschscholtzxanthin are 

 warmed, the absorption bands are displaced. 



Melting point: 185-186° (corr., Berl-block). [ajg^^g = +225° ± 12° (in 

 chloroform). 



Solvent: Absorption maxima: 



Carbon disulphide 536 502 475 mfi 



Benzene 516 485 458 m/j, 



Chloroform 513 484 456 m/^ 



Ethanol 503 472 446 m/j, 



Pyridine 521 489 463 m/z 



On adding concentrated sulphuric acid to a solution of the pigment in 

 chloroform, the latter assumes a blue colouration. No colouration is obtained 

 with concentrated hydrochloric acid. 



Eschscholtzxanthin can be chromatographed on magnesium carbonate or 

 calcium carbonate from carbon disulphide or benzene solution. It is found above 

 zeaxanthin but below capsanthin in the chromatogram. The results so far 

 obtained in these preliminary investigations suggest that eschscholtzxanthin 

 may be a dihydroxy-y-carotene; all its properties are in accord with such a 

 structure. 



Esters of Eschscholtzxanthin 



1. Diacetate: Melts over the range 200-240° with decomposition. 



[a]6678 : + 132° (in chloroform). 



2. Dipalmitate: M.p. 100-110°. 



3. Dibenzoate: M.p. 133°. [ajg^^g = — 142°. 



4. Di-p-nitrobenzoate: M.p. 260° [aj^g^g = — 234°. 



5. Dioleate: Could not be crystallised. 



17. ECHINENONE 



During investigations on the pigments from sea urchin {Strongylocentrotus 

 lividiis*), Lederer^^ isolated a new carotenoid, echinenone. 



For the preparation of echinenone, the sexual glands of sea urchins are ground 

 with sand and extracted at room temperature with acetone. These extracts are 

 combined with those obtained from the back shells of the animals and concentrated 



* In his first communication dealing with echinenone, E. Lederer [Compt. rend. 

 201 (1935) 300] erroneously described the sea urchins as Echinus esculentus. The error 

 was corrected in the second communication®^. 



References p. 341-343. 



