CAROTENOIDS IN LAND PLANTS 



Chemical and spectrographic data on fruit carotenoids are recorded 

 in Table 4 and their qualitative distribution in different species in 

 Table 5. 



Ripening of Fruit 



There is complete agreement amongst numerous workers that the 

 carotenoid content of fruit increases considerably with maturation; 

 for example, the carotene content of red peppers is more than thirty 

 times greater than that of the green peppers ; i s e, i s ? similar results 

 have been obtained with orange rind, i s s, 1 9 o orange pulp, ^ * ' orange 

 juice, ^^* pumpkins (squashes),^ ^^ rose hips (R. spaldingii,^** R. 

 cinnamomea and R. rugosa)^ ^ ^ ^ tomatoes, ^ * * mangoes 1 » a- 1 » • and a 

 number of citrus fruits.^*' 



There does, however, exist one early report that banana skins main- 

 tain a constant carotenoid content during ripening.^** 



Rind or peel of fruit very often is the region of the highest con- 

 centration of carotenoids ; 1 « s, 1 » 7- 2 1 fQj. example, apple peel has a 

 concentration five times greater than that of the flesh, * ^ ^ whilst 50-75 

 per cent, of the total carotenoids of oranges exists in the rind. ^ ^ ' 



The fact that accumulation of carotenoids in maturing fruit is 

 accompanied by a commensurate disappearance of chlorophylls has 

 given rise to considerable speculation on the possibility of the con- 

 version of chlorophylls into carotenoids. This will be dealt with later 

 (see p. 66) for at the moment it is only important to consider the qualita- 

 tive changes occurring in the carotenoid distribution during matura- 

 tion. The overall picture indicates an increase in total carotenoids and 

 an increase in the carotene : xanthophyll ratio (t.e.y the preferential 

 formation of carotenes, especially noticeable in mangoes) ^*'* and an 

 increase in the amount of xanthophylls present as esters. 



Kuhn and Brockmann^'^ showed that the carotenoid distribution 

 in the green sepals of P. alkekengi is very similar to that in green leaves 

 (xanthophylls : carotenes, 3:1). On ripening, artificially in the pre- 

 sence of Oj, lutein (xanthophyll) disappears, carotene increases and 

 physalien appears. 



There is relatively a much higher concentration of carotenes than 

 of xanthophylls in mature orange peel.^^* The lycopene : carotene 

 ratio changes in ripening rose hips.**** However, in the case of 

 Pyracantha angustifolia berries, ripening produced a considerable 

 increase in all pigments except p-carotene which remains at almost the 

 same level ; • ' in ripening palms the a : p-carotene ratio remains 

 constant. ^ * * 



39 



