CAROTENOIDS 



Krause-Voith • that ingested epoxides do not appear in the blood of 

 humans {see p. 250). 



The presence of both carotene and xanthophylls in human blood 

 plasma (but not in the red cells) and milk was first demonstrated by 

 Palmer and Eckles' in 1914, although the presence of lipochromes was 

 first noted in 1869 by Thudichum. ^ According to Palmer* blood 

 carotenes and xanthophylls are attached to proteins ; more recent 

 work^*''^^ has confirmed this and indicated that the pigments are 

 probably attached to an albumin*. That such a carrier-complex is 

 involved is implicit in the results of the work of Chalmers, Goodwin 

 and Morton 12 who found that whilst carotene dissolved in organic 

 solvents is destroyed by ionizing radiations with an ionic yield of almost 

 unity, in plasma the ionic yield drops to 0-01 ; Goldblith and Proctor ^ * 

 have recently confirmed these observations in organic solvents. 



It has not been unequivocally decided whether xanthophylls are 

 free or esterified in human plasma ; Palmer ' considered them to be 

 free but more recent work by Siillman and Vischer^* and by Pratt 

 and Stern ^ ' indicates that they are esterified. 



The suggestion of SuUman and Vischer that some xanthophylls are 

 converted into carotenes as they cross the gut wall is in all probability 

 incorrect. 



The number of reports confirming Palmer and Eckles'' original 

 observation on the presence of carotenoids in blood is legion and it is 

 now considered that blood carotenoids are merely a reflection of the 

 carotenoid intake in the diet : i «- 1 ^ this similarity is carried over into 

 the body fat ^ "■ ^ i and, in general, milk ; 2 1- a ? q^ the average about 

 25 per cent, of the total carotenoids of human milk is made up of a- 

 and p-carotenes, 2 7- 3 2 ^md of this fraction 35-40 per cent, is a- 

 carotene. ®2 With and his collaborators consider that lycopene is not 

 transferred to the milk 28-30 b^t the recent work of Kon and Mawson 2 ' 

 makes this conclusion improbable ; further more, lycopene ic present 

 in human fat ^ ' and blood. ^ * The values obtained for the carotenoid 

 distribution in human milk in war-time Britain are given in Table 41. 

 Kon and Mawson found that although considerable variations occurred 

 from mother to mother the values obtained during a single complete 

 lactation were very constant. It should be noted that although the 

 milk carotenoids generally reflect the blood carotenoids, as stated 

 above, Kon and Mawson's studies revealed some small but important 

 variations. The unknown pigment referred to in Table 41 , separates on 

 chromatography with vitamin A from which it could not be separated ; it 

 had an absorption spectrum with maxima in hexane at 450 and 476 m(x. 



♦p^obulin has recently been reported as the carrier.*** 

 230 



