CAROTENOIDS 



There still remains to be identified the pigment designated " Un- 

 identified II " by Porter and Zscheile^** and which disappeared in 

 advanced generations of the selections containing it ; it appears to 

 contain 8 conjugated double bonds ^ * * and its spectrum is recorded in 



Table 4. 



16 



500 



Wavelength (mfi) 



Fig. 9. — ^The absorption spectrum In hexane of (o) Prolycopene, (b) Pro-y-carotene, 

 (c) Pro-tetrahydroiycopene and (d) Tetrahydrolycopene (Neurosporene). 

 {From Zechmeister, L (1944) Chem. Rev., 34, 267 (o & b), Porter, J. W., and 

 Zscheile, F.P. {1946) Arch. Blochem., 10, 537. (c), and Haxo, F. {1949) Arch. 

 Blochem., 20, 400. (d).) 

 Note. — ^The E values for (c) are only relative. 



(viii) cis-tsomers of the carotenes have been observed in the fruit 

 of tomatoes, i * ». 1 4 e, 1 5 2 tj^g palms Butia capitata and B. eriospatha, ^ • * 

 mangoes, 1 •^ ^' ^ ** ' peaches, papayas, guavas, apricots, v^^ater melons, 

 bananas, pineapples, grapes, musk melons, oranges ^ "^ *• ^ ' * and 

 Pyracantha angustifolia. ^ ^ ^' ^ ^ ^ The most important are neo-^-y 

 P-carotenes B and U^*', prolycopene, ^ *•» ^ **• ^ • • pro-y-carotene^'' 

 and protetrahydrolycopene. ^ * ' The p-carotene isomers have already 

 been discussed (p. 8). Prolycopene and pro-y-carotene are stable 

 pigments which contain, respectively, 5 or 7 and 4 or 5 of their double 



30 



