Naturally Occurring cis and Polycis Carotenoids
As we have seen, the overwhelming majority of plant carotenoids possess the all-trans configuration. To what extent the more energy-rich cis carotenoids appear in plants and animals is a question of biological and genetical interest. The relative scarcity of cis carotenoids in living tissue indicates the presence of some directing and protective mechanism that forms and preserves the all-trans configuration, even when the pigment is exposed to strong sunlight and heat; similar conditions cause trans → cis rearrangements in extracts. After a cis carotenoid has been formed, its configuration is likewise protected in the plant.
KeywordsNone None Ripe Berry Petroleum Ether Solution Central Double Bond Pigment Zone
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