

THE CHLOROPLAST PIGMENTS 



461 



lipochrome; this is probably the reason why 

 the proposed term was never widely used. 



Zopf (1895) used the term carotin 

 synonymously with lipochrome in most 

 of his extensive studies of pigments of the 

 lower forms of plants and animals. He 

 proposed to distinguish between two 

 groups of carotins, namely, eucarotins 

 (true carotins), which were hydrocarbon 

 in nature, and carotinins, which contained 

 oxygen as well. It appears that the 

 carotins are not related to the oxygen- 

 containing xanthophyll which we know 

 at the present time. Tswett (191 1) pro- 

 posed the name "Carotinoide" for the 

 various chromolipoids which are chemi- 

 cally and generically related to carotin. 

 He designated as carotins all those 

 chromolipoids whose constitution and 

 properties show them to be hydrocarbons 

 and as xanthophylls all those whose 

 constitution and properties show them to 

 be oxyhydrocarbons and which are chemi- 

 cally as well as generically related to 

 carotin. The terminology of Tswett has 

 been quite widely adopted and is the one 

 which Palmer has used in his monograph 

 on the carotinoids. The monograph 

 shows the chemical and physiological 

 relation of the carotinoids to the yellow 

 animal chromolipoids of the tissues and 

 fluids of the higher mammals and man and 

 of the egg yolk and bodies of oviparous 

 animals and is probably a criterion of 

 similar relations which extend throughout 

 the entire animal kingdom. 



Carotin as obtained from the carrot root 

 was first described by Wachenroder (i8z6) 

 one hundred years ago. He called the 

 pigment carotin, the same name that we 

 use. Vauquelin and Bouchardat (1830) 

 next studied it. Zeise (1847) first isolated 

 it in quantity sufficient for analysis and 

 also learned much regarding its chemical 

 properties. His analysis showed that it 

 contained only carbon and hydrogen but 



its hydrocarbon nature was not definitely 

 established until Arnaud (1886) made his 

 careful analysis. Kohl (1902.) has given 

 us the most detailed descriptions of the 

 chemical and physical properties of carotin, 

 but his chemical analyses were quite 

 unsatisfactory. Later Willstatter and 

 Mieg (1907) definitely settled the chemical 

 composition of carrot carotin when they 

 proved it to be identical with the carotin 

 of the chloroplast. It was given by them 

 the formula C40H56, which has been 

 generally assumed to be correct. Escher 

 (1909) and Willstatter and Escher (1910) 

 have completely confirmed these results. 

 Escher perhaps is the only investigator on 

 record who has attempted to unravel the 

 structure of carotin. His attempts led 

 only to the production of amorphous 

 products; consequently its constitution 

 still remains to be determined. 



It was Fremy (i860) who first showed 

 that a yellow pigment can be obtained 

 from green leaves. He did this by allow- 

 ing strong hydrochloric acid and ether to 

 act upon the residues from the alcoholic 

 extract of green leaves, or by a similar 

 treatment of the precipitate thrown down 

 from the alcoholic leaf extract by alumi- 

 num hydroxide. In this procedure the 

 ether assumed a yellow color while the 

 acid layer became bluish. Fremy called 

 the yellow color phylloxanthine and the 

 blue pigment phyllocyanine. Stokes 

 (1864) first expressed the view that the 

 phylloxanthine was a mixture of some of 

 the natural carotinoids of the leaf with an 

 acid decomposition product of chlorophyll. 

 It was possibly Fremy who succeeded in 

 obtaining for the first time crystals of 

 carotin and perhaps those of xanthophyll 

 from green plants. Stokes (1864) is 

 credited with first discovering a method 

 for actually separating the yellow pig- 

 ments accompanying chlorophyll; he 

 recognized the existence of distinct green 



