Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: February 12, 2002
Publication Date: N/A
Technical Abstract: Carotenoids are synthesized in the plastids of a plant cell and typically contain forty carbon atoms derived from eight-subunits of the five-carbon compound, isoprene. Larger and smaller carotenoids do occur. Two categories of carotenoids occur in nature. These are the carotenes which contain only carbon and hydrogen, and xanthophylls (also termed oxycarotenoids) which contain carbon, hydrogen, and oxygen atoms. Each carotenoid has its own distinctive color and a few are colorless. Their chemical structure makes carotenoids very insoluble in water but they are fat-soluble. Therefore they are usually associated with cell membranes and lipids, the primary water-insoluble component of cells. Some plant carotenoids occur as crystals in a protein matrix and in some animals carotenoids occur with proteins. The chlorophylls drive photosynthesis and in this process potentially harmful oxidizing compounds are generated. The carotenoids occur in photosynthetic tissues along with chlorophyll to protect them from photooxidative damage. In fact, this protection is essential for photosynthesis. Beyond their important role as a source of vitamin A for humans, dietary carotenoids, including those which are not provitamin A carotenoids, have been implicated as protecting against certain forms of cancer and cardiovascular disease. Two carotenoids which appear to impart health benefits are lycopene and lutein. Poultry, fish, and mammalian food animal diets also are frequently supplemented with natural or synthetic carotenoids to not only provide a dietary vitamin A source but primarily to color meat and animal products and make them more appealing for consumers.