CAROTENOIDS IN LAND PLANTS 



reversal of relative abundance between the carotene and xanthophyll 

 fractions. 



Small amounts of cryptoxanthm (3- or 4-hydroxy-(3-carotene) ^ ' 

 and isolutein also occur in leaves. Isolute'm, a carotenoid of unknown 

 structure has, according to Strain, an empirical formula C4oH5e04 or 

 C4aH8o04 ; it will be interesting to see if, in the light of recent ex- 

 perience, wolutein turns out to be lutein -5 : 6-epoxide (C4oH6e03) 

 which was observed in the leaves of Lotus corniculatus and Arnica 

 montana by Karrer, Jucker and Krause-Voith * • and which is now 

 considered to be a normal component of green leaves. * " 



Me Me Me 



Me Me Me 



Cryptoxanthin (3 or 4-hydroxy-p-carotene) 



Me 



Lutein (xanthophyll) 5:6-epoxide 



Hydroxy carotenoids can occur naturally in the form of esters, as 

 was first shown by Kuhn, Winterstein and Kaufmann. ^^ In fresh 

 green leaves, however, the amount of esterified xanthophylls present is 

 a very small percentage of the total. * ^ 



Although the ratio of a : ^-carotene can differ widely amongst 

 different species (p. 8), Strain ^ 5 has shown that the xanthophyll 

 mixture remains quantitatively and qualitatively the same from species 

 to species. 



One of the most interesting observations made recently is that 

 rhodoxanthin {see p. 32) occurs in the leaves of the gymnosperms 

 Ceratozamia mexicana and Haworthia coarctata v. krausii.^^^ This 

 confirms and gives added interest to the early Tswett observations, 

 and those of Monteverde and Lubimenko*^^, who stated that rhodo- 

 xanthin occurred in the winter foliage of Thuja virginica, Taxus 

 baccatay Cupressus naitnockii, Retinospora plumosa, Juniperus virginiana , 

 and Gnetum sp. 



17 



