CAROTENOIDS IN LAND PLANTS 



by as much as 50 per cent., 3 1 3, 3 3 2 ^j^g j-^^g ^i^^^ increase depending on 

 the variety, and therefore, from this point of view there seems no 

 objection to harvesting them early. ^ ^ ^ 



An interesting recent development in the sweet potato-starch 

 industry has been reported. ^ ^ ^ After extraction with water, the pulp 

 and starch contain only 10 per cent, and '* a trace " respectively of the 

 total carotenoids, the remainder is in the supernatant liquor obtained 

 by filtering off the pulp and removing the starch by centrifugation ; 

 acidification of the liquor produces a coagulum which contains 46 per 

 cent, of the total carotenoids although it represents only 2 per cent, by 

 weight of the original sweet potato. The possibilities of this carotene 

 protein concentrate in practical nutrition have yet to be explored. 



In an extensive study of general cultural factors in their relation to 

 carotene production in carrots. Booth and Dark ^ ^ ^ found that in order 

 to reach their maximum concentration in the autumn carrots had to 

 be sown before the end of May and, in the case of some high carotene- 

 yielding varieties considerably before then. Other interesting points 

 which emerged from this study were that summer sown carrots when 

 harvested in late winter and early spring as " stecklings " have only one- 

 third the normal carotene concentration, that thinning and " chitting " 

 (pregermination on filter paper) had no effect on the carotene pro- 

 duction of the roots, and that carrots produced from newly harvested 

 seeds contain less carotene than do those produced in later seasons 

 from the same seed. 



AQUATIC PHANEROGAMS 



Little work has been carried out on this group of plants ; Hey ^ ^ ^ 

 reported that rhodoxanthin characterized in 1933 by Kuhn and Brock- 

 mann, ^ ' ' was first isolated from Potamogeton natans in 1893 by 

 Monteverdi who, in collaboration with Lubimenko, obtained it crystal- 

 line in 1913. Hey, himself, investigated the carotenoid composition 

 of the leaves of the Canadian pond weed Elodea canadenis, and apart 

 from carotene isolated a new xanthophyll " eloxanthin ", C4oK5e03, 

 m.p. 182-5-183° (X ^^a^, CS2, 444, 473, S02m'^). Recently Karrerand 

 Rutschmann^^ have suggested that eloxanthin is identical with lutein 

 (xanthophyll) -5 : 6-epoxide (see p .17). It was first thought that no 

 lutein was detected in the leaves of this plant, but later work has 

 shown it to be present. ^ " 



57 



