CAROTENOIDS 



is an astaxanthin ester. Recently, Goodwin and Srisukh have re- 

 investigated these pigments and v^^hilst agreeing w^ith Kuhn and his 

 colleagues that the egg pigment is unesterified and hypodermis pig- 

 ment esterified astaxanthin, they cannot agree that the astaxanthin in 

 the carapace is esterified ; they found only the unesterified pigment 

 occurring in combination with protein. Whether these differences are 

 due to the lobsters being obtained from different localities is not known. 

 Owing to keto-enol tautomerism astaxanthin and astacin exhibit 

 acid properties and will dissolve in dilute aqueous alkali. 



Astaxanthin 



It is now certain ^ ^ that astacin never occurs naturally and all reports 

 of its presence are due to its formation by oxidation of astaxanthin 

 during the manipulative processes. Because of this, in this book 

 astaxanthin is always reported although the original workers may have 

 described astacin. 



Kuhn, Stene and Sorensen ^ ^ have given a list of all the sources of 

 astaxanthin recorded up to 1939. It is clear from the work of these 

 workers and that of Stern and Salomon ^^-^^ that ovoverdin and the 

 blue pigment in lobster carapaces are astaxanthin-protein complexes. 

 Ovoverdin is stable between pH 4-8, has an isoelectric point of pH 7, 

 exhibits absorption bands at 640 mfx. and 470 mji,., has one molecule 

 of astaxanthin linked to one molecule of protein, ^ * and according to 

 sedimentation data has a molecular weight of 300,000. ^ ^ The complex 

 is reversibly dissociated by short heating to moderate temperatures in 

 the presence of neutral salts. ^ * 



Astaxanthin was first noted in Nephrops norvegicus by Burkhardt, 

 Heilbron, Jackson, Parry and Lovern ^ ^^ and Lederer and Fabre ; 

 recently Goodwin and Srisukh*' have confirmed this and found that 

 whilst the hypodermal pigment is esterified astaxanthin that of the 

 carapace is not. 



The blue pigment in the ovaries and developing embryo of the goose 

 barnacles Lepas anatifera and L. fascicularis is also a carotenoprotein, 

 the prosthetic group is astaxanthin and the protein an euglobulin. As 

 the nauplii develop, their colour changes from blue to pink and 



170 



