Carotenoids
- 15.11.2015
- English Articles
- Anna Westphal
- Volker Böhm
Peer-reviewed | Manuscript received: January 19, 2015 | Revision accepted: June 03, 2015
Properties, distribution, bioavailability, metabolism and health effects
Chemistry and structure of carotenoids
Carotenoids are fat-soluble colouring compounds widely spread in nature, having various biological functions in plant and also animal organisms. This is mainly due to their chemical structure. Carotenoids belong to the natural poly- unsaturated isoprenoids. Often consisting of eight isoprene units, they form a basic structure of 40 carbon atoms. Thus, many carotenoids belong to the tetraterpenes. At the ends of the carbon chain various functional groups can be located, resulting in the enormous variety of more than 750 carotenoids known today [1]. According to their structure, they are distinguished in oxygen- free carotenes and oxygen-containing xanthophylls (• Figure 1).
The best known carotene is β-carotene, which had been first extracted from carrot juice in 1831 by the German pharmacist and chemist Heinrich Wilhelm Ferdinand Wackenroder at Jena University [2].
Properties
The long polyene structure of carotenoids is responsible for the characteristic colours and the antioxidant properties of this group of compounds. Due to the long chain of conjugated double bonds, blue and green parts of the visible light spectrum are absorbed. Carotenoids do not only give their colour to blossoms, fruits and vegetables, but are also responsible for the strong colours of bird feathers, tropical fishes and shellfishes [1]. By food intake, carotenoids are enriched in various tissues of the animal, like muscles, feathers or beak (• Figure 2).
Summary
As colouring pigments in many fruits and vegetables like tomatoes, carrots, kale, mango or oranges, carotenoids are part of our daily diet. While the secondary plant compounds do not deliver essential nutrients to humans, numerous health-promoting effects are reported. One of the main functions is the provitamin A activity of some carotenoids. Due to their antioxidant potential, carotenoids are connected with a reduced risk of cardiovascular diseases, some kinds of cancer and age-related macular degeneration. Although the data published so far do not allow a recommended intake level, it is suggested to ensure a sufficient supply of carotenoids by eating high amounts of fruits and vegetables.
Keywords: secondary plant compounds, food additives, colouring compounds, antioxidant potential, bioavailability, isoprenoids, carotenoids
