ABSTRACT
Introduction Carotenoids are naturally occurring pigments found in a wide variety of plants, algae and several lower organisms (1), and more than 600 naturally occurring carotenoids have been isolated and characterized (2). Due to an extensive conjugated polyene chain, carotenoids typically are bright yellow, orange, red, or purple with absorption maxima in the range of 400-500 nm (3). These polyisoprenoid compounds are synthesized by plants and .microorganisms and interact with chlorophyll during photosynthesis to absorb light and transfer energy (4-6). Another result of their conjugated polyene chain is the ability of carotenoids to quench singlet oxygen and free radicals and thereby protect plants from photooxidative damage (5,6). Carotenoids have been classified into two groups, hydrocarbon carotenes and oxygenated xanthophylls (7), and the structures of carotenes and xanthophylls that are common in the human diet are shown in Figure 8.1.
