326 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



regenerated by treatment with thiosulphate. Echinenone gives no blue 

 colouration with concentrated aqueous hydrochloric acid in ethereal solution. 



l8. PECTENOXANTHIN 



Lederer^® investigated the pigments which occur during the develop- 

 ment of the sexual organs of St. Jacques shell {Pecten maximus) and discovered 

 a new carotenoid for which he proposed the term pectenoxanthin*. 



For the isolation of pectenoxanthin, the finely cut sexual organs of the shells 

 are treated with acetone. Water is added and the pigments are extracted from the 

 solution with petroleum ether. They are transferred to 90 % methanol and the 

 solution is strongly concentrated in vacuum. On diluting the methanolic residue 

 with a little petroleum ether, pectenoxanthin crystallises out. For further purification 

 the pigment is adsorbed on a column of calcium carbonate and then crystallised 

 from a mixture of pyridine and water. From 500 sex organs about 50 mg of pure 

 pectenoxanthin were obtained in this way. 



No conclusive evidence is at present available regarding the chemical 

 constitution of pectenoxanthin. The molecular formula appears to be C40H54O3 

 (ih Hg). Microhydrogenation showed the presence of 11 double bonds. Zere- 

 WITINOFF determination yielded a quantity of methane corresponding to 2 

 atoms of active hydrogen. Thus it appears that 2 oxygen atoms are present in 

 the form of hydroxyl groups. The nature of the third oxygen atom is as yet un- 

 known. The pectenoxanthin molecule does not appear to contain an unsub- 

 stituted j3-ionone ring as the compound exhibits no vitamin A activity. 



Solvent: Absorption maxima: 



Carbon disulphide 518 488 454 m^ 



Benzene 496 464 434 mn 



Petroleum ether 488 458 vafi 



The pigment crystallises from aqueous pyridine in long yellow-brown 

 prisms, m.p. 182". Pectenoxanthin is adsorbed above zeaxanthin on calcium 

 carbonate. The pigment is much more readily soluble in 90 % methanol than 

 in petroleum ether. It is readily soluble in benzene, carbon disulphide and 

 pyridine. With concentrated sulphuric acid it produces a deep blue colouration. 

 No colouration is observed with aqueous hydrochloric acid. 



19. pentaxanthin 



Besides echinenone, Lederer isolated a further previously unknown 

 pigment, pentaxanthin, from sea urchin {Sirongylocentrotus lividus)^''. 



* P. Karrer and U. Solmssen, Helv. chim. Acta 18 (1935) 915 discovered a caro- 

 tenoid which exhibits similar absorption maxima as pectenoxanthin in pecten jacobaeus. 

 The two pigments are possibly identical. 

 References p. 341-343. 



