chapter  23
Pages 73

Carotenoids are of widespread occurrence as natural

pigments in plants and animals; they contribute the

natural yellow, orange, and red colors of many plants

as well as being used extensively as nontoxic natural or

nature-identical colorants in foodstuffs (1). Their name

is derived from -carotene, the main representative of their group, which was first isolated from

carrots (Daucus carota) by Wackenroder in 1831 (2).

Carotenoids are isoprenoid polyenes which are formed

by head-to-tail linkage of C5 isoprene units, except for

one tail-to-tail linkage in the center of the molecule,

which makes it symmetrical (3). The C40 carotenoids

can be divided into carotenes, which are hydrocarbons

(e.g., -carotene, Fig. 1a) and their oxygenated derivates, the xanthophylls (e.g., zeaxanthin, Fig. 1b).

Fruit xanthophylls are often acylated with fatty acids

(4). Besides the C40 carotenoids there are also apocar-

otenoids, a degraded form with less than 40 carbon

atoms in the skeleton, and higher carotenoids where

the carbon skeleton contains 45 or 50 carbon atoms,

respectively (5). The characteristic absorption spectrum of each

carotenoid is determined by the chromophore, a

series of conjugated double bounds. Usually the

spectrum shows three absorption bands, which are

affected by the length of the chromophore, the nature

of the double bound and the taking out of conjunction