I LYCOPENE 117 



residue is dried at 40-50°, finely ground and continuously extracted with carbon 

 disulphide. The solvent is removed by distillation, finally under reduced pressure 

 at 40° in an atmosphere of dry carbon dioxide, which is passed in through a capillary. 

 The dark reddish brown paste which remains is diluted with 3 1 ethanol when 

 crystallisation immediately sets in. After a short time the crystalline mass is filtered 

 and the residue washed with cold petroleum ether. The crude lycopene can be 

 purified either by dissolution in carbon disulphide and precipitation with ethanol, 

 or bv recrystalUsation from a large volume of petroleum ether (b.p. 50-80°, 4-5 1 

 per 1 g of lycopene). For analysis, the material is first crystallised from petroleum 

 ether, any sparingly soluble components being rejected, and then recrystallised from 

 carbon disulphide, or a mixture of carbon disulphide and ethanol, without further 

 fractionation. Using this procedure, 11 g of once recr\'stallised lycopene can be 

 obtained from 75 kg of preserves, whereas Willstatter and Escher obtained 

 2.7 g of pigment from 135 kg of fresh tomatoes. Thus 1 kg of fresh fruit yields 0.02 g 

 of lycopene, while 1 kg of preserves yields 0.15 g of lycopene. Some commercial 

 preserves contain acidic materials which have a deleterious effect during the iso- 

 lation of Ivcopene. By addition of potassium carbonate to the tomato puree, Kuhn 

 and Grundmann^ were able to improve the yield of lycopene considerably. From 

 1 kg of preserves they obtained 0.2G5 g of pigment. 



According to Zechmeister and vox Cholxoky^, lycopene can also be isolated 

 from Tamils communis berries. 



Chemical Constitution 

 CH, CH, CH3 CH3 



C ' CH3 CH3 CH3 CH3 c 



y I I I I \ 



•CH CH-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CH CH 



CHj C-CH3 H3C-C CHj 



\^ / Lycopene \ y^ 



CH2 CH2 



Willstatter and Escher^*' recognised that lycopene is an isomer of caro- 

 tene and determined the correct empirical formula, C40H56. The constitution 

 of the pigment was elucidated by Karrer and his co-workers^. The results 

 of these investigations can be briefly summarised as follows. 



The deep red colour of lycopene suggested the presence of numerous double 

 bonds. Karrer and Rose Widmer^^ found that 13 mols of hydrogen were 

 absorbed during the catalytic hydrogenation of the pigment. The empirical 

 formula of perhydrolycopene was C40H82, which showed that lycopene must 

 have an open-chain structure (cf. the corresponding discussion of carotene). 

 According to Pummerer, Rebmann and Reindel^^^ lycopene absorbs 13 

 mols of iodine chloride, thus confirming the presence of thirteen ethylenic 

 bonds. Karrer and Bachmann^^ ^nd Karrer, Helfenstein, Pieper and 

 Wettstein^* found that ozonisation affords considerable quantities of acetone. 

 One mol of the pigment gave 1.6 mols of ketone, suggesting the presence of 

 References p. id^-iyo. 



