CAROTENOIDS 



melons, ^*^ and 1:8m European peaches. ^'"^ On the other hand, 

 Hunter and his colleagues ^ * ^' ^ * * found only small amounts of 

 lycopene in red palm oil. According to Brockman ^^^ the apricot 

 contains only 2-3 mg. per cent, (wet wt.) of lycopene compared with 

 50-80 mg. per cent, of ^-carotene. It is interesting to note at this point 

 that whilst apricots contain only carotenes, ^^^ xanthophylls pre- 

 dominate in peaches. ^ ^ •- 



(v) ^-carotene. Winterstein ^ * * gave the name S-carotene to a 

 fraction obtained from the fruit hulls of Gonocaryum pyriforme. It 

 also occurs in traces in ordinary tomatoes ^ * ^ {Ly coper sicum esculentum)^ 

 but crosses of L. esculentum and L. pimpinellifolium can contain up to 

 40 (jLg. of S-carotene/g. fruit. ^ * * From such crosses Porter and 

 Murphey ^ * ' have recently been able to isolate S-carotene in crystalline 

 form (Table 4). It contains eleven double bonds ten of which are 

 conjugated, one closed ring (which cannot have the p-ionone con- 

 figuration because the pigment has no Vitamin A activity) and one open 

 ring. Winterstein had previously suggested the following structure for 

 S-carotene. This cannot be completely reconciled with the findings 

 of Porter and Murphey ^ * ', although it may well be near the truth. 



(vi) Z,- carotene. A carotenoid, first isolated from carrots by Strain 

 in 1939 1*^ {see p. 54) and which, although not yet prepared in a 

 completely pure state, has been well characterized chromatographic- 

 ally, 1 * ». 1 6 spectroscopically ^ ^ ^ and chemically, ^ ^ ^ jg ^-carotene. 

 The suggestions'^'' that because of the similarity in the position of 

 their visible absorption bands ^-carotene and aurochrome (Karrer 

 and Jucker s ^ ^' s '^ ') are probably identical, has been disproved by 

 carrying out mixed chromatograms with the two pigments. Auro- 

 chrome is much more tightly absorbed than is ^-carotene, ^ ' ^ which 

 has now been shown to be in all probability 5 : 6, 7 : 8, 5' : 6', 7' : 8- 

 octahydrolycopene^^^ and to have no vitamin A activity. ^^^ 



26 



