Carotene: Difference between revisions

Carotene is an orange photosynthetic pigment important for photosynthesis. It is responsible for the orange colour of the carrot and many other fruits and vegetables. It contributes to photosynthesis by transmitting the light energy it absorbs to chlorophyll.

Chemically, carotene is a terpene. It is the dimer of retinol (vitamin A) and comes in two primary forms: α and β-carotene. γ, δ and ε-carotene also exist. Carotene can be stored in the liver and converted to vitamin A as needed.

Carotenemia

Main article: Carotenodermia

Carotenemia or hypercarotenemia is excess carotene, and unlike excess Vitamin A is non-toxic. Although hypercarotenemia is not particularly dangerous, it can lead to a yellowing of the skin (carotenodermia). It is most commonly associated with consumption of an abundance of carrots, but it also can be an medical sign of more dangerous conditions. A randomised trial into the use of beta carotene and Vitamin A for treatment of lung cancer had to be stopped early due to the apparent increase in the incidence of lung cancer^[1].

The two forms

α-carotene

α-carotene

β-carotene

β-carotene can be found in yellow, orange, and green leafy fruits and vegetables. These can be carrots, spinach, lettuce, tomatoes, sweet potatoes, broccoli, cantaloupe, orange, and winter squash. As a rule of thumb, the greater the intensity of the color of the fruit or vegetable, the more beta-carotene it contains.

β-carotene is an anti-oxidant and such can be useful for curbing the excess of damaging free radicals in the body. However, the usefulness of β-carotene as a dietary supplement (i.e. taken as a pill) is still subject to debate^[2]. β-carotene is fat-soluble, so a small amount of fat is needed to absorb it into the body.

Carotenoids

Carotenes are un-oxidized carotenoids. Carotenoids in which some of the double bonds have been oxidized are known as xanthophylls.

Production

Most of the world's synthetic supply comes from a manufacturing complex located in Freeport, Texas and owned by the DSM corporation.

Nomenclature

The two ends of the β-carotene molecule are structurally identical, and are called β-rings. Specifically, the group of nine carbon atoms at each end form a β-ring.

The α-carotene molecule has a β-ring at one end; the other end is called an ε-ring. There are no "α-rings".

These and similar names for the ends of the carotenoid molecules form the basis of a systematic naming scheme, according to which:

• α-carotene is β,ε-carotene;
• β-carotene is β,β-carotene;
• γ-carotene (with one β ring and one uncyclized end that is labelled psi) is β,ψ-carotene;
• δ-carotene (with one ε ring and one uncyclized end) is ε,ψ-carotene;
• ε-carotene is ε,ε-carotene,

References

1. ^ Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease
2. ^ Questions and Answers About Beta Carotene Chemoprevention Trials

External links

• Beta-carotene website by Martha Evens, School of Chemistry, University of Bristol
• Berkeley Wellness Guide to Dietary Supplements
• Beta-caroten on University of Maryland
• Carotenoids on Herbal Phytochemistry