Carotenoids

Carotenoids are natural fat-soluble pigments found in certain plants. Carotenoids provide the bright red, orange, or yellow coloration of many vegetables, serve as antioxidants, and can be a source for vitamin A activity. There are more than 600 known natural carotenoids, all of them synthesized only in plants. Carotenoids may be classified as hydrocarbon carotenes or xanthophylls, which are oxygenated derivatives of carotenes. Representative examples of carotenes include β-carotene, alpha-carotene, and lycopene. Examples of xanthophylls include lutein, astaxanthin, canthaxanthin, zeaxanthin, and capsorubin. Lycopene, lutein, zeaxanthin, phytoene, phytofluene and beta-carotene belong to this family. Carotenoids are antioxidants. They play an important role in health maintenance by helping to reduce the impact and minimize the oxidative damage caused by surplus free radicals.

Carotenoids are characterized by a large (35-40 carbon atoms) polyene chain, sometimes terminated by rings. Carotenoids where some of the double bonds have been oxidized such as lutein and zeaxanthin, are known as xanthophylls; the un-oxidized carotenoids such as alpha-carotene, beta-carotene and lycopene are known as carotenes. Probably the most well-known carotenoid is the one that gives this group its name, carotene, found in carrots and responsible for their bright orange colour. Carotenoids are a highly colored (red, orange, and yellow) group of fat-soluble plant pigments. All organisms, whether bacteria or plants, rely on the sun for energy contain carotenoids.

Their color, ranging from pale yellow, through bright orange, to deep red, is directly linked to their structure: The double carbon-carbon bonds interact with each other in a process called conjugation. As the number of double bonds increases, the wavelength of the absorbed light increases, giving the compound an increasingly red appearance.

Carotenoids are fat-soluble compounds formerly called lipochromes. Their nutraceutical significance is attributed to their well documented antioxidant properties. Their antioxidant effects enable these compounds to play a crucial role in protecting organisms against damage during photosynthesis, the process of converting sunlight into chemical energy. In photosynthetic organisms, carotenoids play a vital role in the photosynthetic reaction centre. They either participate in the energy-transfer process, or protect the reaction center from auto-oxidation. In non-photosynthetic organisms, carotenoids have been linked to oxidation-preventing mechanisms.

Health benefits of carotenoids

Carotenoids are very important for health. The health benefits of carotenoids in the human diet are becoming increasingly apparent. There've been studies suggest that some carotenoids can offer protection against some cancers, macular eye disease and cardiovascular problems. A higher dietary intake of carotenoids offers protection against developing certain cancers (e.g., lung, skin, uterine, cervix, gastrointestinal tract), macular degeneration, cataracts, and other health conditions linked to oxidative or free radical damage. In addition to being antioxidants, carotenoids also help to rejuventate the body by promoting the growth of healthy cells and inhibiting the growth of unhealthy ones. The beneficial actions of carotenoids are optimal when a variety of carotenoids are consumed together, rather than alone.

Carotenoids are converted to vitamin A mainly in the intestine and liver. About 10% of dietary carotenoids are converted to vitamin A in the body and contribute 25% of our total vitamin A. Of the 600 carotenoids that have been identified, about 30 to 50 are believed to have vitamin A activity. Carotenoids the body converts to vitamin A are referred to as "provitamin A" carotenoids. The most well known of this group are beta-carotene and alpha-carotene. Many carotenoids are antioxidants that protect cells against free radicals by neutralizing them before they cause oxidative damage.

As antioxidants, carotenoids protect cells from damage by unstable oxygen molecules called free radicals. Lycopene and beta-carotene, taken along with vitamins C and E, may help protect the body against the effects of chemotherapy or radiation.

All carotenoids help to prevent heart disease and heart attack by inhibiting the formation of harmful LDL cholesterol. Because they are very soluble in fat and very insoluble in water, carotenoids circulate in lipoproteins along with cholesterol and other fats. Carotenoids are able to absorb light in the visible range of the spectrum. By filtering out the sun's harmful ultraviolet (UV) rays and by keeping free radicals from damaging the retina, carotenoid may help to protect against macular degeneration. Reducing the amount of blue light that reaches the structures of the eye that are critical to vision may protect them from light-induced oxidative damage.

Major carotenoids

Beta-carotene

Beta-carotene is one of the orange dyes found in most green leaves, and in carrots. Carotene is a terpene, an orange photosynthetic pigment, important for photosynthesis. Carotenes are hydrocarbons and most are found in yellow, orange, and red vegetables. Beta-carotene is made up of eight isoprene units, which are cyclised at each end. Beta-carotene is the most potent precursor to vitamin A. Beta-carotene is considered a conditionally essential nutrient. Beta-carotene becomes an essential nutrient when the dietary intake of retinol (vitamin A) is inadequate.

Lycopene

Lycopene is a carotenoid responsible for the red color of the tomato, watermelon and pink grapefruit. It has a unique long chain molecular structure containing 13 double bonds, more than any other carotenoid. This configuration is responsible for lycopene's special ability to neutralize free radicals. It is a very potent anti-oxidant, detoxifier, and helps inhibit the production of cholesterol. Lycopene is more than twice as powerful as beta-carotene at quenching free radicals.

Lutein and zeaxanthin

Lutein is a carotenoid pigment found in many green vegetables, and is usually derived from marigold flower petals. Lutein and zeaxanthin belong to the xanthophyll family of carotenoids and are the two major components of the macular pigment of the retina. kale and broccoli. Zeaxanthin is a stereoisomer of lutein, differing only in the location of a double bond in one of the hydroxyl groups. Lutein is found in high concentrations in the eye, and has been shown to protect against blindness caused by macular degeneration. Lutein and zeaxanthin, which are naturally present in the macula of the human retina, filter out potentially phototoxic blue light and near-ultraviolet radiation from the macula.

Dietary sources of carotenoids

Carotenoids are naturally present in edible leaves, flowers, and fruits, and are readily obtained from flowers (i.e. marigold), berries, and root tissue (i.e. carrots). In general, the greater the intensity of color, the higher the level of carotenoids. Hydrocarbon carotenes, such as β-carotene and lycopene, are typically present in an uncombined free form, which is entrapped within chloroplast bodies within plant cells. Xanthophylls, such as lutein, are abundant in a number of yellow or orange fruits and vegetables such as peaches, mango, papaya, prunes, acorn squash, and oranges. Food sources of lutein and zeaxanthin, include corn, egg yolks and green vegetables and fruits, such as broccoli, green beans, green peas, brussel sprouts, cabbage, kale, collard greens, spinach, lettuce, kiwi and honeydew.

Lutein and zeaxanthin are also found in nettles, algae and the petals of many yellow flowers. Lycopene is found in raw (unprocessed) tomatoes is contained within a matrix. The richest sources of beta-carotene are yellow, orange, and green leafy fruits and vegetables (such as carrots, spinach, lettuce, tomatoes, sweet potatoes, broccoli, cantaloupe, and winter squash). Generally, the free forms of carotenoids are present in the chlorplasts of green plants such as alfalfa, spinach, kale and leafy green plant materials. The free form of the carotinoids provides better adsorption when consumed in foods or as a supplement.

Astaxanthin belongs to a group of pigments (colouring agents) called carotenoids. It is the principal pigment that gives salmonids their pink colour. It is produced for addition into fish feed in the latter part of the production cycle to ensure a good flesh colour. Astaxanthin is in the class of phytonutrients known as carotenoids, the best known carotenoid is beta-carotene. Astaxanthin is similar in structure with beta-carotene. Other carotenoids include lutein and lycopene. Astaxanthin is another significant and potent carotenoid. Astaxanthin isolated from crustacean wastes or produced synthetically. Astaxanthin can also be farmed from unicellular green alga called Haematococcus pluvialis or certain types of yeast and then prepared for commercial use.

Astaxanthin is the major carotenoid responsible for the pink-red pigmentation of fish and shrimps. Asthaxanthin is an important element of the feed chain of wild and farmed salmon and shrimp. This microalgae is part of the diet of fish or crustaceans and is responsible of the pink coloration in their flesh, through the ingestion of astaxanthin. Astaxanthin benefits fish and shellfish in several ways, including protection against oxidation of essential polyunsaturated fatty acids, protection against the effects of ultra violet light, enhanced immune response and improved reproduction.

A powerful antioxidant

Astaxanthin performs all three of the key antioxidant tasks including quenching, scavenging, and trapping free radicals, and enhances the activity of other antioxidant nutrients. Astaxanthin provides a greater protection of the cellular membranes than β-carotene, vitamin C and vitamin E. Astaxanthin neutralises free radicals as it traps them inside its structure. Astaxanthin traps more kinds of free radicals, including singlet and triplet oxygen. Its antioxidant activity is far higher than vitamin E and β-carotene.

It also may protect against UVA light, a wavelength of ultraviolet light that can cause sunburn and skin cancer. It stabilizes free radicals by adding them to its long double-bonded chain, rather than sacrificing an atom or electron. And it is absorbed by the mucosa in the small intestine and transported to the liver where it binds with a lipoprotein and is efficiently transported throughout the body.

Health benefits of astaxanthin

Astaxanthin has been claimed to be ten times more effective than beta carotene and 100 times more effective than vitamin E in preventing lipid peroxidation. Astaxanthin protects the cellular and mitochondrial membranes and the ocular tissues against the photo-oxidative damage to DNA, involved in AMD pathogenesis. Carotenoids can help protect the retina from oxidative damage. The free radical scavenging activity of astaxanthin protects lipids from peroxidation and reduces oxidative damage of LDL-cholesterol (thereby reducing arterial plaque formation), cells, cell membranes, mitochondrial membranes.

Astaxanthin increases strength and endurance. Astaxanthin is one of those important carotenoids and might be beneficial for nerve damage associated with age-related macular degeneration. Astaxanthin may easily cross the blood brain barrier and could have antioxidant effects in the brain. Astaxanthin might exert beneficial effects in protection against hypertension and stroke, and could improve memory in vascular dementia. Astaxanthin has a peculiar chemical structure. Astaxanthin enhances the cellular membranes stability as it locates crosswise inside them.