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Carotenoids

Carotenoids are natural pigments that are responsible for many of the yellow, orange, and red colors seen in living organisms. Carotenoids are widely distributed in nature and perform a number of important biological functions, including protecting organisms from photo-oxidative damage. The carotenoids include carotene, lycopene, bixin, zeaxanthin, cryptoxanthin, lutein, canthaxanthin, beta-carotenal. Carotenoids are lipids universally found in the photosynthetic tissue of higher plants, algae and photosynthetic bacteria. They are found spasmodically distributed in flowers, fruits, roots of higher plants and fungi and bacteria. Carotenoids are tetraterpenoids, consisting of eight isoprenoid residues and can be regarded as being synthesized by the tail to tail dimerization of two 20 carbon units each themselves produced by head to tail condensation of four isoprenoid units. Hydrocarbon carotenoids are termed carotenes and oxygenated carotenoids are known as xanthophylls. Oxygenated carotenoids are widespread in nature and occur, inter alia, in corn (zeaxanthin), in green beans (lutein), in capsicum (capsanthin), in egg yolks (lutein) and in crabs and salmon (astaxanthin), in which case they give the characteristic coloration to these foods. Beta-carotene is probably the best known of the carotenoids. The carotenoid class of substances is classified into two main groups, carotenes and xanthophylls. In contrast to the carotenes, which are purely polyene hydrocarbons, for example beta-carotene or lycopene, in the xanthophylls, oxygen functions, such as hydroxyl, epoxy and/or oxo groups also occur. In the human body carotenoids provide powerful antioxidant action. Antioxidants help form the body's defense against free radicals, which develop as a result of normal metabolism as well as from exposure to pollution and other environmental hazards. Typical representatives of this group are, inter alia, astaxanthin, canthaxanthin, lutein and zeaxanthin. Carotenoids possess significant nutritional value, carotenes and cryptoxanthin being considered as a provitamin A precursor for the formation of retinal and Vitamin A in humans. Vitamin A, an essential vitamin, for life is not synthesized in the animal cell. An especially important member of the carotenoid class of compounds is beta-carotene. Beta-carotene is not only useful as a colorant (typically yellow, orange and especially red in color) but also provides a valuable source of vitamin A. For this reason, beta-carotene is often included in foods and beverages as a colorant, especially where vitamin A fortification is needed or desired. Extracted or enriched carotenoids can be used as nutraceuticals, dietary supplements, or pharmaceuticals. The nutraceuticals industry employs liquid organic solvents to extract carotenoids and lipids from natural substrates.

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