Apocarotenoids animals

Apocarotenoids also act as chemoattractants, repellants, and growth effectors in plants and cyanobacteria. They attract pollinators to plants through the use of color similar to full-length carotenoids. Their aromas are thought to be attractants for animals and insects to facilitate in seed dispersal and pollination. Small volatile apocarotenoids lure pollinators and levels of apocarotenoids... 

Davies (1976) has reviewed the new system of nomenclature of carotenoids. Figure 1 shows the basic structure and numbering system for (3-, a-, and y-carotenes and for cryptoxanthin, the major carotenoids contributing to the vitamin A activity in animal and human foods. Apocarotenoids are compounds that have been shortened by removal of at least one end of the molecule beyond a designated location. In general, they have less biological activity than P-carotene (see Table I). 

On the basis of structure alone, Simpson and Chichester (1981) estimate that 50-60 carotenoids and apocarotenoid compounds could have provitamin A activity. Only a few of the identified carotenoids, however, have both vitamin A activity and occur in significant amounts in natural foods as commonly eaten by vertebrate animals (Bauemfeind, 1972). Of these, p-carotene has by far the most provitamin A activity. The a- and y-carotenoids and cryptoxanthin (3-hy-droxy-P-carotene), also found in substantial amounts in commonly consumed foods, have about one-half the activity of the P form. Table I contains a list of the provitamin A activity found in the most important mammalian food sources of carotenoids. Table II lists vitamin A-inactive carotenoids commonly found in food. 

The basic and most important biologically active apocarotenoid in animal tissues is aU-trans-retinol also known as axeroftol or vitamin Aj (5-1). Retinol is an isoprenoid with 20 carbon atoms and five conjugated double bonds in the molecule, more precisely a diterpenic ahcychc alcohol with the so- called fl-ionone ring and a side chain of four conjugated double bonds attached to C-6. It is one of 16 possible stereoisomers. 

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