CAROTENOIDS IN PLANTS 



concluded that two fucoxanthins existed in the Phaeophyceae, but 

 later 1 2 9 he agreed with Heilbron and Phipers that one of his pigments 

 was an oxidative artefact. Recently Strain and his colleagues 1 * 6. 1 4 e 

 have reopened the question, and as previously noted, they claim 

 that two labile isomers exist in addition to fucoxanthin itself. These 

 they have named neofucoxanthin A and neofucoxanthin B according 

 to Zechmeister's nomenclature {see p. 10); the status of these pigments 

 is still obscure (see p. 131). They also noted the presence of diatoxanthin, 

 diadinoxanthin, violaxanthin and probably flavoxanthin. 



I50i 



lOQO 

 Icm. 

 500 



400 



420 



440 460 480 



Wavelength (mfi) 



500 



Fig. 21.— The absorption spectrum of (0) Fucoxanthin in hexane. (- 



{Redrawn from Karrer, P., ar)d Wurgler, £. (1943) Helv. chim. Acta, 26, 

 117, (b) Neofucoxanthin B {from Strain, H. H., Manning, W. M., and 

 Hardin, G. {1944) Biol. Bull.Woods Hole, 84, 169). ( ) 



Further confusion arose following the examination of dried Fucus 

 vesiculosus by Heilbron and Phipers. ^^^ They found, rather sur- 

 prisingly, no fucoxanthin but zeaxanthin instead, and concluded this 

 was a post mortem change. Kylin, ^^^ however, claims that both 

 zeaxanthin and violaxanthin are pre.sent in fresh F. vesiculosus ; the 

 failure to detect them in fresh material is considered to be due to the 

 overwhelming preponderance of fucoxanthin ; Kylin goes on to claim 

 that in dead material fucoxanthin is preferentially oxidized, thus 

 unmasking zeaxanthin. 



Heilbron's ^ ^ * objections to Kylin's explanation are : (a) the absence 



133 



