CAROTENOIDS OF THE C40 SERIES 



589 



from the eggs of the North American lobster {Homarus americanus) , is 

 stable from a pH of 4 to one of 8; it has an isoelectric point at a pH of 6.7, 

 while its approximate molecular weight is 300,000. The name ovoverdin 

 has been proposed for this chromoprotein.^-^ 



A somewhat simple protein-carotenoicl complex has been described by 

 Ball^-" in the eggs of the goose barnacle {Lepas fascicularis L. anatifera). 

 A dissociation of the blue-colored complex into the colorless protein and the 

 red carotenoid apparently accounts for the change in color observed in 

 these embryos. Ball^-^ believes that the prosthetic group of the chromo- 

 protein is astaxanthin. A salt bridge combination of the pigment with 

 protein, through the hydroxy 1 groups, similar to that suggested for ovover- 

 din, is assumed. 



Ovoverdin 

 (green) 



thermal 



acids 



Astaceue ester + Native protein 

 (orange-red) 



theiinal 



organic solvents (orange-red) 



* Astacene ester + Denatured protein 



salt 



-> Coagulated 

 protein 



alkali 



light 



-> Astacene + Organic acid 



-> Photodecomposition products (colorless) 



light 



Plioto decomposition products 

 (l/eUou') 



developments 



-* Shell pigment 

 (blur) 



> Hvpodermis pigment 



(red) 



Fig. 1. The reactions of ovoverdin. ^^^ 



Astaxanthin is closely related to astacene, which is formed when ovover- 

 din is broken down by acids or by heat. The simpler pigment does not 

 occur as the protein complex. Prestmiably astacene has been reported in a 

 number of ca.ses whereas, as a matter of fact, the naturally occurring pig- 

 ment actually was astaxanthin in the form of ovoverdin; in these cases 

 astacene developed only as a result of chemical procedures occurring during 

 its isolation. Figure 1 demonstrates the relationships between the pig- 

 ments in lobster egg.^-^ 



a. Structure. Astaxanthin has an empirical formula of C40H52O4. It 



«6 E. G. Ball, J. Biol. Chcm., 152, G27-G3-1 (1941). 



