89 - 



the spectral absorption maxima, and the sorbability on activated sor- 

 bents increase with the number and the conjugation of the double bonds. 

 Some of these relationships are indicated by Table IV, I. Lycopene, 

 with 13 double bonds 11 of which occur in a single conjugated system, 

 is more intensely colored, redder and much more sorbed than (3-oarotene, 

 with 11 conjugated double bonds. But (3-carotene, with its 11 conjugated 

 double bonds, in redder and more sorbed than CX-carotene, with 11 double 

 bonds only 10 of which are conjugated with single bonds. 



At Tswett' s time, the crystalline xanthophyll then isolated from 

 leaves by Willstfiter and his associates appeared to be an oxygen deriv- 

 ative of carotene. The greater sorption of the xanthophylls relative 

 to carotene could be attributed to the oxygen atoms. Several decades 

 later when the chemical combination or function of the oxygen atoms was 

 determined, the sorbability of the xanthophylls was related to the pres- 

 ence of particular structural units such as hydroxyl (SC-OH), keto (=C«0) 

 and epoxy (»C^-\*) groups^* ^'^»^°. 



Among the xanthophylls, the relative sorbability, as reflected by 

 the sorption sequence, is related not only to the number and conjugation 

 of the double bonds, to the number of oxygen atoms, and to the function 

 of the oxygen atoms but also to the solvent and the sorbent-*--'-*-'. Table 

 IV, II shows the molecular structures of four common xanthophylls, rhodo- 

 xanthin, zeaxanthin, lutein, and crypt oxanthin. Table IV, II I shows the 

 effect of variation of the sorbent and of the solvent upon the sorption 

 sequence of these xanthophylls and the three carotenes of Table IV,!. 

 The brackets in Table IV,III indicate pigments that were not separated 

 from one another. 



