CAROTENOIDS 



pollen has fermented, the ** bee-bread " so produced has a vitamin 

 A-activity of 6 i.u./g. ^ » « Very recently, Karrer, Eugster and Faust * • ' 

 have surveyed the distribution of carotenoids in the pollen and anthers 

 of a number of species ; their observations are summarized in Table 10. 

 It appears that esterified lutein (xanthophyll) is always the principal 

 carotenoid component of pollen with p-carotene always present 

 in traces. Except in the case of Helianthus tuberosus^ epoxides were 

 absent. In anthers, on the other hand, especially in Lilium spp. 

 detectable amounts of epoxides (in particular, cis-antheraxanthin) were 

 always encountered. A xanthophyll, perhaps esterified with different 

 acids, occurred in a sample of deep orange beeswax, the principle 

 pollen contaminant of which was probably from Delonix regia, * • • 



ROOT CAROTENOIDS 

 (i) Carotenes 



The most important roots from the carotenoid view-point are the 

 carrot and the sweet-potato. The common potato contains only traces 

 of carotenoids,^*^** which have also been reported in the roots of beet, ' • • 

 Brassica campestrts,^'^^'^^^ and B. rapa.^^^ The carrot, as its name 

 suggests, was the first recognized source of carotene which was obtained 

 crystalline by Wackenroder in 1831. ^^'^ Since then reports of investi- 

 gations on carotene in carrots have been legion and the reader is 

 referred to Zechmeister's treatise for a discussion of the early work. ' <* * 

 In 1931 carrot ** carotene " was resolved into 2 isomers, a- and p- 

 carotene^^'^^* and since then Mackinney, Aronoff and Bomstein*®* 

 found a-carotene to constitute between 5 and 10 per cent, of the total 

 carotene fraction of carrots, whilst Kemmerer and Fraps*"' found 

 between 19-5 and 42-2 per cent, and Fujita and Ajisaka ^ 36-45 per cent.; 

 Harper and Zscheile ^ ° ' reported even higher values giving an average 

 figure of 46 per cent. Sadana and Ahmad^®^ obtained very similar 

 results in India, but correlated the a-carotene content with the colour 

 of the carrot. Red varieties contained between 10 and 16 per cent, of 

 a-carotene and orange varieties between 34 and 51 per cent. If the 

 higher values just quoted are correct, carrots generally contain more 

 a-carotene than do green leaves, for the highest value found in plants 

 by Mackinney was 35 per cent. ^ * Minor constituents of the carotene 

 fraction of carrots are, y-carotene (0-1 per cent, of total caro- 

 tenoids), ^ ^ ^' ^ ° " d-carotene, lycopene^^^ (V^^ the concentration of 

 ^-carotene), ' ^ ' and ^-carotene, i ^ o, 3 o 9 Qf these S-carotene, ^-carotene 

 and lycopene do not occur in the carrot leaf. 



Investigations on the carotene content of carrots have been far 



54 



