r.VROTENOLS AND OXYCAROTENOL.S OF THE C40 SERIES 555 



The (lilferenccs between the two component.s of the egg-yolk hitein, 

 kitein (xanthophyll) and zeaxanthin, seem to be similar to the variations 

 between a- and /3-carotenes. Both lutein and zeaxanthin are isomeric 

 dihydroxy -carotenes with the hydroxyl substituted at 3 and 3'. Lutein is 

 weakly dextro-rotatory, while zeaxanthin is optically inactive. It would 

 appear, therefore, that lutein is a dihydroxy-a-carotene (3,3'-dihydroxy-/3, 

 a '-carotene), while zeaxanthin is a dihydroxy- j8-carotene (3,3'-dihydroxy- 

 /3,/3 '-carotene). For these reasons, Karrer, Zubrys, and IVIorf^*^ have pro- 

 posed the following formula for lutein (xanthophyll), while Karrer^**^ has 

 suggested that zeaxanthin possesses the structure indicated here. The 

 close structural relationship between lutein and zeaxanthin is illustrated by 

 the fact that the former can be changed to zeaxanthin by heating in an 

 evacuated tube at 100-1 10°C. for 30 hours with benzene, sodium, and 

 absolute alcohol. ^^^ a-Carotene is partially changed to /3-carotene by 

 similar treatment. 



HjC CHj HjC CHj 



Q CHj CHj CHj CHj r 



/ \ hh|hhhIhhhhIhhhIhhh/\ 

 HjC C-c:C'C:C'C:C'C:C'C:C'C;C'C:C-C:C'C:C'C chj 



H.I II I l/H 



c c c c 



"" C CH, HjC C 



Hz H 



Lutein 



HjC CHj H5C CHj 



n CHs CH3 CH3 CHi Q 



/\ hhIhhhIhhhhIhhhIhh /\ 

 HzC c«c:C'C:c«c;C'C:C'C:c-c;c-c:c-c:c-c:c-c chj 



H\l II II l/H 



c c c c 



^«/ \ / \ ■ / \ / \„^ 



"0 C CHj HjC C O" 



Hz Hz 



Zeaxanthin 



b. Occurrence. Lutein is especially widely distributed in nature. In 

 common with chlorophylls a and b and carotene, it is present throughout 

 the plant kingdom.-^ Willstatter and StolP^'^ were able to isolate 0.68 to 

 1.25 g. of lutein from one kilogram of dried leaves. It was shown that 1.5 

 to 2.0 molecules of this carotenol were present for each molecule of carotene, 

 giving a carotene to lutein ratio which averaged 0.6. This is illustrated by 

 the results of Willstatter and StolP*^ given in Table 4. 



2*5 p. Karrer, Arch. sci. biol. Italy, 18, 30-39 (1933). 



2«« P. Karrer and E. Jucker, Helv. Chim. Acta, 30, 266-267 (1947). 



2*' R. Willstatter and A. Stoll, U ntersuchungen uber Chlorophyll, Methoden und Ergeh- 

 nisse, Springer, Berlin, 1913. Cited bv L. Zechmeister, Die Carotinoide, Springer, Berlin, 

 1934, pp. 72, 74, 169. 



