1. CAROTENOIDS

The amazing variety of colors of living organisms brings not only aesthetic pleasure, but also indicates the high biological significance of pigments.

Some of the most striking natural pigments in terms of beauty and biological activity are carotenoids. These are fat-soluble compounds synthesized by plants, algae, bacteria and fungi (Sandmann, 2001). Their research began back in 1831, when Wackenroder isolated the yellow pigment β-carotene in crystalline form from carrots, and in 1837 Berzelius isolated yellow pigments from autumn leaves and called xanthophylls. 100 years later, in 1933, 15 different carotenoids were already known, about 80 in 1947, and over the next twenty years this value exceeded 300. Currently, the group of carotenoids includes about 700 pigments. In nature, these substances determine the color of falling leaves, the color of flowers (daffodils, marigolds) and fruits (citrus fruits, peppers, tomatoes, carrots, pumpkin), insects ( ladybug), bird feathers (flamingo, ibis, canary) and marine organisms(shrimp, salmon). These pigments provide a variety of colors: from yellow to dark red, and when combined with proteins they can produce green and blue colors.

In plants they are secondary metabolites and are divided into two groups: oxidized xanthophylls such as lutein, zeaxanthin, violaxanthin and carotenoid hydrocarbons such as β- and α-carotenes and lycopene.

Among the known plant pigments, carotenoids are the most common and are characterized by structural diversity and wide range biological action. In higher plants, carotenoids are synthesized and localized in cellular plastids, where they are associated in light-sensitive complexes, participating in the process of photosynthesis and protecting plants from oxidative stress caused by excess light.

Of the 700 known carotenoids, 40 are constantly present in human food; only β-carotene, alpha-carotene and cryptoxanthins have provitamin (A) activity in mammals.

Carotenoids are considered to be one of the most powerful singlet oxygen scavengers. It is the antioxidant properties of these compounds that largely determine their biological activity. Although carotenoids are present in many traditional foods, the richest human sources are brightly colored vegetables, fruits and juices, with yellow-orange vegetables and fruits providing the bulk of β- and α-carotene intake. orange fruits are sources of α-cryptoxanthin, dark green vegetables - lutein, peppers - capsanthin and capsorubin, and tomatoes and their processed products - lycopene Johnson, 2002.

According to the level of accumulation of carotenoids among vegetable crops The leaders are spinach, rich in lutein and zeaxanthin, as well as representatives of the genus Capsicum, containing capsanthin and capsorubin in fruits.

Among exogenous factors, the accumulation of carotenoids is significantly influenced by growing temperature, light intensity, length of the photoperiod and the use of fertilizers. It is known that in the shade the content of lutein and β-carotene in plants is lower than in the light, and in the summer grown kale has higher concentrations of these carotenoids than when grown in winter period. As they grow, the content of carotenoids in the leaves increases and decreases at the aging stage, that is, the amount of carotenoids in the plant also depends on the time of harvest. Experimental studies confirm that organic farming provides the greatest accumulation of red and yellow pigments in sweet pepper fruits (Table 2).

Due to their antioxidant properties, carotenoids attract Special attention in the fight to prevent chronic diseases such as cancer, cardiovascular disease, diabetes and osteoporosis.

Table 2. Carotenoid content in fruits of sweet peppers of the Almuden variety under the use of organic fertilizers, traditional and integrated technologies (mg/kg fresh weight) (Perez-Lopez et al, 1999)

Carotenoid	Organic farming	Integrated farming	Traditional farming
General content	3231	2493	1829
Red faction*	2038	1542	1088
Yellow faction	1193

*red fraction = capsorubin + capsanthin and isomers

Yellow fraction = β-carotene + β-cryptoxanthin + zeaxanthin + violaxanthin

The most important biological function of carotenoids in the human body is provitamin (A) activity. Carotenoids with such activity 1) support the differentiation of healthy epithelial cells, 2) normalize reproductive functions and 3) vision. Vitamin A is a component of the visual pigment rhodopsin, which explains the important role of β-carotene, α-carotene and cryptoxanthins in maintaining vision. In particular, a lack of vitamin A in food can lead to the development of so-called “night blindness”, characterized by a significant decrease in the sensitivity of the retina at dusk, and in severe cases to the development of so-called “tubular” vision, when the light-sensitive cells of the peripheral part of the retina stop working . Lutein and zeaxanthin are two of the 7 carotenoids found in blood plasma and are the only carotenoids found in the retina and lens. In the retina, lutein and zeaxanthin are responsible for yellow pigmentation and are called macular pigments. This area occupies only 2% of the entire surface of the retina and consists exclusively of cone cells responsible for color vision. It has been suggested that macular pigments are involved in photoprotection, and reduced levels of lutein and zeaxanthin may be associated with retinal damage. Increasing the amount of these pigments can be achieved by increasing the consumption of antioxidants, vegetables and fruits, food carotenoids, normalizing body mass index and quitting smoking. Many of these factors are also associated with a reduced risk of age-related macular degeneration, suggesting a cause-and-effect relationship. Research shows that increasing the proportions of lutein and zeaxanthin, as well as lycopene, reduces the risk of macular degeneration. It should be especially noted that high levels of consumption various vegetables Supplementing the body with a variety of carotenoids reduces the risk of eye disease more powerfully than consuming individual carotenoids.

In general, data from epidemiological studies suggest a positive relationship between high levels of carotenoid intake and a low risk of chronic, cardiovascular diseases, some forms of cancer, and the level of immunity.

Studies of the anticarcinogenic effect of carotenoids have revealed a protective effect of β-carotene against lung cancer in non-smokers and especially in men. Consuming high doses of carotenoids reduces the risk of some types of lymphoma, but does not affect the risk of developing bladder cancer. Lycopene may prevent prostate cancer.

Risk reduction cardiovascular diseases under the influence of carotenoids is due to the protection of low-density lipoproteins from peroxidation and a decrease in the intensity of oxidative stress in places where atherosclerotic plaques are localized. Cohort studies have established the protective role of dietary carotenoids against cardiovascular disease in Italy, Japan, Europe and Costa Rica.There is a number of studies confirming the protective effect of lycopene in preventing cardiovascular diseases. Epidemiological studies on 662 patients and 717 healthy people from 10 different European countries showed a dose-dependent relationship between lycopene intake and the risk of myocardial infarction. When comparing the levels of lycopene consumption in Lithuania and Sweden, an increase in the risk of development and mortality from coronary heart disease was shown in conditions of insufficient lycopene consumption. As it turned out, lycopene in tomatoes, sauces, ketchups, tomato juice significantly reduces the level of oxidized forms of low-density lipoproteins and reduces cholesterol levels in the blood, thereby reducing the risk of cardiovascular diseases.

Prevention of cancer with the consumption of high doses of carotenoids is associated with the ability of the latter to inhibit cell proliferation, their transformation and modulate the expression of determinant genes. Oxidized carotenoids (such as β-cryptoxanthin and lutein) as well as non-oxidized forms (such as β-carotene and lycopene) are associated with a reduced risk of cancer. Studies on cell cultures have shown that, in addition to β-carotene, some other carotenoids may exhibit anticarcinogenic activity, and in some cases the activity is higher than β-carotene (for example, capsanthin, α-carotene, lutein, zeaxanthin, etc.).

About 90% of all carotenoids in food and the human body are represented by β- and α-carotene, lycopene, lutein and cryptoxanthin. Lycopene is one of the main carotenoids in the Mediterranean diet and provides up to 50% of all carotenoids in the human body. Among vegetables, tomato is the main source of lycopene, and tomato-based products (ketchup, tomato paste, sauces) provide a person with 85% of all lycopene coming from food. The anti-carcinogenic properties of lycopene have been confirmed by epidemiological studies, studies in vitro and on laboratory animals, as well as on humans.

The main mechanisms of the anticarcinogenic effect of lycopene are believed to be participation in the deactivation of reactive oxygen species, regulation of the detoxification system, influence on cell proliferation, induction of cellular interactions, inhibition of the cell cycle and modulation of signal transduction.

In general, about 10-30% of lycopene is absorbed by humans. Positive influence The level of lycopene absorption is influenced by the presence of fat-soluble compounds, including other carotenoids. Surprisingly, the spatial configuration of the central double bond of the lycopene molecule determines the intensity of its absorption. It has been shown that cislicopene, formed during heat treatment tomato, is absorbed more efficiently than the trans isomer of raw fruit. Cis isomers are also formed in the body of humans and animals when trans forms are consumed.

In addition to blood serum, lycopene accumulates in significant quantities in the testicles, adrenal gland, prostate and mammary glands, as well as the liver.

The anti-carcinogenic properties of tomato lycopene are manifested against cancer of the prostate, breast, cervix, ovary, liver, lungs, gastrointestinal tract, and pancreas.

Due to their antioxidant properties, carotenoids are able to protect the body from other pathological conditions associated with oxidative stress. Epidemiological studies show that β-carotene and lycopene, together with vitamins C and E, significantly reduce the risk of osteoporosis. This fact seems especially important in the prevention of osteoporosis in women during menopause, which is characterized by a significant decrease in antioxidant protection.

The positive effect of lycopene in reducing systolic pressure in hypertensive patients, who are characterized by the development of oxidative stress, has been established.

Male infertility is known to be associated with the formation of a significant amount of reactive oxygen species in sperm, while in healthy men no reactive oxygen species were detected in the seed. Considering that the content of lycopene in the semen of infertile men is lower than that of healthy individuals, an attempt was made to correct the supply of lycopene. Consumption of 8 mg of lycopene per day by such patients for a year significantly increased sperm motility, improved their morphology and ensured 5% of cases of conception.

The role of lycopene in the development of neurodegenerative diseases such as Alzheimer's disease is currently being investigated. Thanks to high level oxygen uptake, high lipid concentrations and low antioxidant capacity, the human brain is highly vulnerable to the effects of oxidants. It has been shown that lycopene is present in low concentrations in nervous tissue, and its concentration is reduced in Parkinson's disease and vascular dementia. In Japan, the protective effect of tomato lycopene against the occurrence and development of emphysema has been established. It is expected that the protective effect of lycopene may occur in patients with diabetes, skin diseases, rheumatoid arthritis, periodontal diseases and inflammatory processes. The antioxidant properties of lycopene also open up wide possibilities for its use in the pharmaceutical, food and cosmetic industries.

Lycopene is still not considered an essential nutrient, and therefore optimal levels consumption is not approved. However, based on data from studies of the protective effect of lycopene, it can be stated that daily consumption to combat oxidative stress and prevent chronic diseases should be 5-7 mg (Levin, 2008). In the presence of diseases such as cancer or cardiovascular disease, it is advisable to increase lycopene intake levels to 35-75 mg. Actual lycopene intake levels are 3-16.2 mg/day in the US, 25.2 mg in Canada, 1.3 mg in Germany, 1.1 mg in the UK, and 0.7 mg in Finland.

Carotenoids
Biological effect	Disease Prevention
Provitamin activity	Night blindness
Deactivation of reactive oxygen species	Cataract
Regulating the detoxification system	Osteoporosis
Effect on cell proliferation	Cancer
Induction of Cellular Communications	HIV
Inhibition of disease cell cycle	Cardiovascular diseases
Modulation of signal transmission	Rheumatoid arthritis
Maintaining immunity	Skin diseases
Participation in the metabolism of drugs	Protection against other inflammatory diseases

2. FLAVONOIDS

The biodiversity of nature is inexhaustible.

Another group of antioxidants, polyphenols, constitute an even larger group of natural compounds (more than 8000 of them are known) (Ross & Kasum, 2002).

Bioflavonoids. Brief information

Bioflavonodes or vitamin P. Vitamin P (from the Latin “paprika” - pepper and “permeabilitus” - permeability) belongs to the family of bioflavonoids. This is a very diverse group of plant polyphenolic compounds that affect vascular permeability in a similar way to vitamin C.

Sources: lemons, buckwheat, chokeberry, black currant, tea leaves, rose hips, onions, cabbage, apples.

Daily requirement for humans has not been precisely established.

Biological role consists in stabilizing the intercellular matrix of connective tissue and reducing capillary permeability.

Close interest in bioflavonoids has arisen recently due to epidemiological studies that have revealed the protective effect of vegetables and fruits containing bioflavonoids on the development of socially significant chronic non-infectious diseases: cardiovascular and malignant. Numerous experiments have shown that flavonoids:

1. have antioxidant properties;
2. prevent the development of atherosclerotic damage to arterial walls by suppressing processes within cellular lipid peroxidation;
3. inhibit platelet aggregation;
4. prevent oxidative damage to nucleic acids and prevent the development of carcinogenesis processes. It is believed that flavonoids also have antiallergic, anti-inflammatory (inhibit COX 1 and COX 2), antiviral and antiproliferative effects.

Clinical manifestation of hypovitaminosis Vitamin P deficiency is characterized by increased bleeding gums and pinpoint subcutaneous hemorrhages, general weakness, fatigue and pain in the extremities.

Drugs plant origin containing flavonoids have found widespread clinical use in the treatment of liver diseases: these can be simple infusions medicinal plants, such as sandy immortelle flowers or concentrated extracts - flamin (dry sandy immortelle concentrate), conviflavin (from the Far Eastern lily of the valley herb). The complex preparation silymarin (contains a mixture of milk thistle bioflavonoids) has a hepatotropic and antitoxic effect and is used for toxic liver damage.

So, Flavonoids are the largest class of plant polyphenols. Polyphenols are a class of chemical compounds characterized by the presence of more than one phenolic groups per molecule. Phenols- organic compounds of the aromatic series, in the molecules of which the hydroxyl groups OH− are bonded to the carbon atoms of the aromatic ring.

These are the most common in flora antioxidants. Alone flavonoids(hydroxy derivatives flavone ) are capable of exerting anti-inflammatory, antiviral, hormonal, antimutagenic effects, protecting against cancer and exhibiting other great amount properties beneficial to humans. It has been established that all natural polyphenols in vegetables have an anticarcinogenic effect.

Action of flavonoids:

• Anti-inflammatory
• Anticarcinogenic (protection against lung and breast cancer)
• Antiviral
• Antioxidant
• Cardioprotective
• Hormonal
• Antiulcer
• Antidiarrheal
• Antispasmodic
• Improved memory, learning and cognition
• Neuroprotective
• Reducing the risk of osteoporosis

The role of flavonoids in maintaining human health is enormous. Epidemiological studies indicate that consumption of fruits and vegetables is associated with a reduced risk of developing chronic diseases, including cardiovascular disease and cancer. It is assumed that flavonoids and other polyphenols are the most important biologically active compounds that determine the positive effects of vegetables and fruits on human health.

Epidemiological studies confirm the protective effect of flavonoids against cancer and cardiovascular diseases (Ghosh & Scheepens, 2009). A significant difference was found in the mortality of populations with high (China) and low (North America, Europe) consumption of flavonoids. Only 2 of 7 large-scale studies did not find a significant protective effect, and both studies were conducted in Europeans with low flavonoid intake. 14 of 19 studies showed an inverse correlation between breast cancer incidence and blood flavonoid levels. Consumption of foods rich in flavonoids is associated with lower rates of heart disease, heart attacks, cancer and other chronic diseases. An inverse correlation has been shown between flavonoid intake and the risk of stroke, lung and colorectal cancer (Trichopoulos, 2003; Hirvonen et al, 2001). Because these chronic diseases are associated with increased oxidative stress and flavonoids are potent antioxidants in vitro, it is hypothesized that dietary flavonoids exert beneficial effects by enhancing antioxidant defenses. The antioxidant activity of flavonoids is manifested in an increase in the antioxidant status of plasma, a protective effect against vitamin E, erythrocyte membranes and low-density lipoproteins, as well as protection of PUFAs of erythrocyte membranes from peroxidation.

The results of numerous studies suggest that flavonoids exhibit antiallergenic, antiviral, anti-inflammatory and vasodilatory activities in humans. Flavonoids, including quercetin And taxifolin, have a beneficial effect on the gastrointestinal tract, exhibiting antiulcer, antispasmodic and antidiarrheal activity. It has been shown that the consumption of vegetables and fruits with high content polyphenols reduces the risk of occurrence and development of osteoporosis.

It has been established that quercetin protects against HIV infection and prevents the oxidation of high-density lipoproteins, thus reducing the risk of cardiovascular diseases. Consuming a significant amount of foods containing quercetin (onions, grapefruit, apples) reduces the risk of developing lung cancer.

Wide range of biological effects of plants of the genus Allium(Table 1) is associated not only with the presence of sulfur-containing compounds, but also with a high concentration of flavonoids. Consumption of onions inhibits the growth of tumors and microbial cells, reduces the risk of cancer, deactivates free radicals and protects against cardiovascular diseases. High antioxidant activity of all onion crops has been established (Kim & Kim, 2006; Corzo-Martinez et al, 2007).

Table 1. Biological effects of plants of the genus Allium

Biological effect	Total number of works	Number of human studies
Cardioprotective
Antimicrobial
Anti-carcinogenic
Antioxidant
Hypoglycemic
Anti-inflammatory

So nine epidemiological studies in different parts globe(China, Italy, Argentina, USA, etc.) clearly showed a significant reduction in the risk of gastrointestinal cancer with increasing garlic consumption (You et al, 1989; Buiatti et al, 1989). The latest observation is related to the ability of garlic to reduce nitrite levels in gastrointestinal tract(precursors of carcinogenic nitrosamines) and bacteriostatic effect against Helicobacter pylory, causing the development of ulcers and stomach cancer (Lanzotti, 2006). The protective effect of allyl di- and trisulfides of plants of the genus has been shown Allium for liver cancer caused by aflatoxin.

Carotenoids are a large class of natural pigments necessary for the normal functioning of most biological organisms. These substances, numbering more than 600 varieties, are among the most abundant organic compounds on the planet. However, most higher mammals, including humans, cannot synthesize carotenoids in their own bodies, so it is extremely important to obtain sufficient doses of these substances from the outside. Before answering the question: “carotenoids - what are they?” Information on sources of carotenoids should be consulted.

Sources of carotenoids

The first representatives of this class of pigments were discovered back in 19th century in tissue analysis carrots and pumpkins. Exactly from English name carrots ( carrot- carot) and the name of the entire group of substances was formed.

“Almost all vegetables and fruits that are yellow, orange and red are sources of carotenoids.”

Very soon it was discovered that many plants and some animals that are yellow and red in color accumulate significant amounts of carotenoids in their bodies. The following products are suitable for replenishing these compounds in the body:

But when eaten raw vegetables and fruits on average only 1% is absorbed mass of carotenoids contained in them. Preliminary thermal(cook, fry) and mechanical(cut, grate) a processing that destroys the cell walls of plant tissues. It is also recommended to consume such foods together with fats (for example, sunflower oil), which will increase digestibility useful substances by 25%.

However, it is worth considering that not all yellow-red pigments are equally useful. Often their effectiveness may differ 1000 times. Therefore, for those who want to maintain youth and health, it is extremely important to know which carotenoids are the most beneficial? and how best to use them.

Comparison of carotenoids

All carotenoids have a complex effect on the human body:

• Counteracting the formation of free radicals (antioxidation);
• Stimulation of the endocrine system;
• Strengthening cell membranes;
• Source of vitamin A (provitamin);
• Improving calcium absorption;
• Stimulation of immunity and more.

On this moment there are only fragmentary research, analyzing the effectiveness of parts of carotenoids relative to each other. In particular, the antioxidant properties of these substances are being intensively studied.

A significant part of the experiments indicate that the most beneficial among them is Astaxanthin, a pigment maximum content which is located in salmon fish and some microorganisms. In a number of experiments, this compound is tens and hundreds of times superior to its competitors, but its concentration in natural products is extremely low. Fortunately, modern pharmacology has found a way out of this situation.

“Only a small portion of the carotenoids it contains can be absorbed from food.”

Dietary supplements based on carotenoids

The digestibility of this group of substances can be increased by creating highly concentrated preparations based on natural raw materials. And while extracting carotenoids from carrots or oranges is quite simple, in the case of astaxanthin, scientists had to rack their brains.

Since the optimal source for obtaining one of the most powerful antioxidants is microalgae

The review article by V.G. Ladygin and G.N. Shirshikova outlines modern ideas about the functions of carotenoids - yellow, red and orange pigments - in plants. Carotenoids play a very important role in the functioning of the molecular machinery of photosynthesis. They perform three main functions: photoprotective (protect chlorophyll and other vulnerable components of photosystems from light “overexcitation”), light-harvesting (which allows plants to use light energy in the blue region of the spectrum - a task that chlorophyll cannot cope with without the help of carotenoids) and structural ( serve as necessary structural elements, “building blocks” of photosystems).

Carotenoids are a widespread class of pigments found in bacteria, unicellular eukaryotes, fungi, plants and animals. Unlike a number of other pigments, such as heme (which colors the blood and muscles of mammals red) or chlorophyll (responsible for the green color of plants), carotenoid molecules do not contain metals. They consist only of carbon, hydrogen and oxygen, and their ability to “work” with light quanta is determined by a system of conjugated double bonds between carbon atoms arranged in a chain. Double bonds separated by one single bond are called conjugated.

Carotenoids absorb light with a wavelength of 280–550 nm (these are green, blue, violet, ultraviolet regions of the spectrum). The more conjugated double bonds there are in a molecule, the longer the wavelength of light absorbed. The color of the pigment changes accordingly. Carotenoids with 3–5 conjugated double bonds are colorless and absorb light in the ultraviolet region. Zeta-carotene with seven bonds is yellow, neurosporin with nine bonds is orange, and lycopene with 11 bonds is orange-red.

The functions of carotenoids in living nature are not limited to working with light; sometimes they play an important role in metabolism (remember, for example, vitamin A, a derivative of beta-carotene). And yet, their main functions (whether in the visual organs of animals or in chloroplasts - the organelles of plant photosynthesis) are inextricably linked with light. The article by Ladygin and Shirshikova examines the role of carotenoids in chloroplasts - plant cell organelles that originate from symbiotic cyanobacteria. The main function of chloroplasts is photosynthesis, that is, the production of organic matter from carbon dioxide using the energy of sunlight. The membranes of chloroplasts contain protein-pigment complexes - photosystems I and II, which include various proteins, as well as pigments - chlorophylls and carotenoids.

Chlorophyll, the main photosynthetic pigment, itself is capable of absorbing and using light only in the red region of the spectrum (650–710 nm). Carotenoids absorb blue-green light and transfer its energy to chlorophylls. This function of carotenoids is light-gathering- is especially important for algae, since blue-green light penetrates much deeper into the water column than red light.

The second function of carotenoids in chloroplasts is light-protective. They protect photosystems from light “overloads”, which can lead to overexcitation and malfunction of photosystems. Carotenoids serve as a kind of “emergency valves” that allow you to release excess energy and convert it into heat. Carotenoids cope with this task in several ways. different ways: simply “filtering” the incoming light, absorbing excess light energy, or removing energy from overexcited chlorophyll. Carotenoids can also “quench” reactive oxygen species, that is, they serve as antioxidants.

One of the ways in which carotenoids “shed” excess energy when exposed to excess light is through cyclic chemical reactions, during which some carotenoids are converted into others. The most common of these reactions is called the violaxanthin cycle. In strong light, the carotenoid violaxanthin is converted to zeaxanthin, releasing oxygen. When light levels decrease, zeaxanthin is converted back to violaxanthin and oxygen is absorbed. Both reactions - direct and reverse - are catalyzed by enzymes whose genes are located in the chloroplast chromosome, and not in the central (nuclear) genome of the plant cell.

The third function of carotenoids is structural. Carotenoids are essential structural components of photosynthetic membranes of chloroplasts. It has been experimentally shown that without carotenoids, photosystems become unstable. Carotenoid molecules occupy strictly defined positions in photosystems, and without them the entire structure simply falls apart.

The authors note that much has become known about carotenoids in recent years, but a number of details remain to be elucidated. In particular, the evolutionary origin of carotenoids, as well as biochemical and photochemical reactions with their participation, is not yet fully understood. It is unclear to what extent carotenoids can be used in phylogenetics, that is, to reconstruct the paths of evolutionary development of organisms. In many older studies, sets of carotenoids characteristic of a particular group of organisms were used as an important taxonomic character. It is not entirely clear how reliable such signs are, especially considering that the same carotenoids can be found, for example, in plant chloroplasts and in the eyes of mammals.

Carotenoids are lipophilic pigments that are localized in chloroplasts and chromoplasts in plants. They are synthesized by all organisms that carry out oxygenic photosynthesis: cyanobacteria, algae, and higher plants. In addition, many mushrooms synthesize and accumulate carotenoids; for example, chanterelles contain significant amounts of (3-carotene and canthaxanthin. Animals, for the most part, are not able to synthesize carotenoids. Therefore, they obtain the carotenoids they need for normal metabolism from plants.

Structure and biosynthesis of carotenoids

Most carotenoids - tetraterpenoids built from eight isoprene units - have a carbon chain consisting of 40 carbon atoms. In many carotenoids, the carbon polyisoprene chain cyclizes at the ends, forming several types of ionone rings. More than 600 carotenoids are known. They differ in the location of their light absorption peaks, which, however, are always within the range of 400-550 nm (violet-green). Carotenoids are divided into carotenes, consisting only of carbon and hydrogen atoms, and xanthophylls, which also contain oxygen atoms in the form of hydroxy, methoxy, epoxy or keto groups.

Carotenes are usually orange in color. The most common are a- and (3-carotenes (Fig. 57). A-carotene has (3- and -ionone rings, and (3-carotene) has two (3-ionone rings. Many plants contain lycopene - carotene has a bright -red in color, without ionone rings. Lycopene is an intermediate in the synthesis of carotenoids, including a- and (3-carotenes.

Xanthophylls vary in color from pale yellow to dark red, although they get their name from the Greek word xanthos, meaning yellow. For example, astaxanthin (Fig. 57) gives a bright scarlet color to the petals of adonis, and capsanthin and capsorbin color the fruits of pepper Capsicum in dark red color. The most common yellow pigments among xanthophylls are lutein, zeaxanthin and violaxanthin. Canthaxanthin and astaxanthin (Fig. 57) are widely known for their antioxidant properties.

Apocarotenoids, the products of oxidative cleavage of the carbon chain of carotenoids, are of great functional importance. In plants, the studied apocarotenoids are 8"-apocarotinal, as well as phytohormones: abscisic acid and strigolactone. Animals and humans need retinal, retinol and retinoic acid - retinoids, collectively called vitamin A (Fig. 57).

Rice. 57.

In plants, the synthesis of carotenoids occurs in plastids, where these pigments usually remain: in green leaves these are chloroplasts, and in fruits, flower petals, and roots - chromoplasts. First, geranylgeranyl diphosphate is synthesized from prenyl C5 blocks with the participation of isopentenyltransferase - geranylgeranyl diphosphate synthase (Fig. 58). The two molecules of geranylgeranyl diphosphate are then joined tail to tail by phytoene synthase. Next, colorless phytoene is desaturated and converted into the red pigment lycopene with a system of conjugated double bonds. Lycopene, under the influence of specific cyclases, can be converted into a- or (3-carotene. Carotenes, in turn, serve as precursors of xanthophylls, into which they are converted using various oxygenases: hydroxylases, epoxidases and others. In addition, the carbon chain of carotenoids can

Encyclopedia "Biology"

Carotenoids

Natural pigments of yellow, orange or red color, synthesized by bacteria, fungi and green plants. They are divided into carotenes and xanthophylls. Carotenes, by chemical nature, are unsaturated hydrocarbons, the molecules of which are built from 40 carbon atoms. Spinach leaves, carrot roots, and rose hips are rich in carotenes. Animals usually do not synthesize carotenes and obtain them from food, accumulating them in adipose tissue. egg yolk, milk, etc. Vitamin A is formed from carotene (provitamin A) in the animal body. Xanthophylls are oxidized derivatives of carotenes (alcohols, aldehydes, etc.). Contained in various plant organs and in the cells of many microorganisms. Carotenoids serve as additional pigments during photosynthesis, participate in photodependent reactions of plants (for example, in tropisms), and color (together with other pigments) the autumn foliage of plants.

encyclopedic Dictionary

Carotenoids

(from Latin carota - carrot and Greek eidos - species), a group of natural pigments of yellow or orange color. By chemical nature - isoprenoids; unsaturated hydrocarbons (carotenes) or their oxidized derivatives (xanthophylls). They are synthesized by some microorganisms and all plants, in the cells of which they participate in photosynthesis and processes associated with light absorption (phototaxis, phototropism, etc.). They determine the color of fruits, autumn leaves, and colonies of a number of microbes. In the body of animals and humans, vitamin A is formed from carotenes supplied with food.