Theme XVII: Plant pigments

Carotene

Carotene. Characterization, types and functions. Carotenoids. Lycopene, crocetin, crocin, phylloxanthins, xanthophyll. Structure. β-carotene, β-ionone.

Carotene C40H56, is one of the most important groups of carotenoids, natural pigments which owe their color to a large number of unsaturated carbon atoms, arranged successively. They are also known as polyenic pigments.

Carotene is mainly in three forms, α, β, γ. It gives carrots their color and is associated with the chlorophyll in green leaves.

The most important is the β-carotene and is formed by four isoprene groups and two cycles equal to those of β-ionone.

β-carotene

β-ionone

The carotene is converted in the organism into vitamin A, by what is known as provitamin A.

Other carotenoids are lycopene (C40H56) composed of 8 isoprene moieties with 13  double bonds found in tomatoes; and the crocetin, a diacid in a linear chain of 16 carbon atoms with 7 double bonds and 4 groups methyl forming diester gentiobiose disaccharide (α-D-glucose-6-β-D-glucoside) is the crocin pigment of saffron.

By oxidation of carotene other pigments are formed, the phylloxanthins. The most important is the xanthophyll (C40H56O2) yellow color and can be found along with chlorophyll and carotene in green leaves.

Carotene has great importance for human health because of its medicinal properties such as reducing the chances of heart attacks, functions as a soluble antioxidant and increases the efficiency of the immune system. It’s used as ultraviolet protector. Taken orally, has been proved that can reduce the likelihood of incidence of some cancers.

See also