CAROTENE

From Big Medical Encyclopedia

CAROTENE (Latin carota carrots) — the yellow-orange vegetable pigment turning as a result of enzymatic transformation to vitamin A (Retinolum); has oxidizing properties, and also is the growth-promoting factor necessary for animals and the person.

In a human body carotene is laid in a liver, heart, adrenal glands, testicles, ovaries, nervous tissue, a placenta. Accumulation To. in different bodies tells about participation it in a metabolism of these bodies. Assume that To. has antihistaminic properties (solution oxidized To. shows antihistaminic action in concentration 1:20 000), stimulates activity of gonads, promotes manifestation of effect of adrenaline, synthesis flying fat to - t in a liver, suppresses effect of pepsin, trypsin, acetylcholine, cathepsine, increases activity of a succinatedehydrogenase and increases the speed of glycolysis.

Those treat the category of karotin carotinoids (see) which represent «pure» hydrocarbons, i.e. contain in the structure only H and S atoms, unlike carotinoids which structure, in addition to H and S atoms, includes oxygen atoms. The cyclic remains which are on one or on both ends of C40 skeleton are a part of a molecule of karotin. Such carotinoids carry the name of cyclic; them β-carotene, a cleavage product is a typical example to-rogo and vitamin A is.

In a blood plasma of the person contents To. depends on its receipt with food and usually fluctuates within 80 — 230 mkg of %. In placental blood concentration To. can reach 96 mkg of %, in umbilical blood — 90 mkg of %. Content To. in blood sharply goes down (to 8 — 30 mkg of %) at many diseases (to a spr, eczema, a hyperthyroidism) and at childbirth. To. contains also in colostrum, and its concentration quickly decreases at transformation of colostrum into milk, Concentration To. in milk always below, than in blood, the Increased consumption To, conducts to an intensive xanthopathy (yellow coloring) owing to adjournment To. in epidermis (aurantiaz; a pseudoicterus, or the xanthemia which is followed by a carotenemia). Carotenemia (see) has no harmful effect on a human body though often accompanies a myxedema (see. Hypothyroidism ). At patients with a diabetes mellitus the xanthopathy is caused by the increased content To. in blood. Children acquire To. it is worse, than adults. Assimilation To, children is broken at pneumonia, sepsis, etc. Stay at big heights leads to reduction of contents To. in a blood plasma of the person.

To. it is for the first time allocated in 1831. It is synthesized in 1950 shveyts. researcher Karrer (R. Karrer). Transformation To. into vitamin A it was experimentally proved in 1929 — 1930. Theoretically two molecules of vitamin A by accession of two water molecules can be formed of each molecule of β-carotene. It is proved that in a human body, rats, a Guinea pig, a rabbit, a cow, a pig, hens and fishes To. can turn into vitamin A. However the mechanism of this transformation is investigated a little. It is supposed that this process proceeds with the participation of enzyme of a carotenase. Practically from one molecule of beta carotene two molecules of Retinolum are impossible. Requirement in To. mammals have enough, than in vitamin A. Many researchers consider that process of transformation To. in vitamin A hydrolytic decomposition of the central double bond in a molecule of p-carotene, then beta oxidation since a final double bond before formation of a retinaldegid and recovery includes to Retinolum (see).

Changes in structure of the cyclic remains at not changed C40 skeleton lead to formation of isomers K. — α, β, γ, δ, ε, (see. Isomerism ). Feature To., as well as other carotinoids, a large number of double bonds in their molecules is that is the reason of their easy oxidability oxygen of air and causes elektronoaktseptorny and electron-donor properties of carotinoids; participation is explained by it To. in biol, oxidation-reduction processes: Important feature To. the easy stereoisomerization and education a trance - and cis-isomers is. The phenomenon cis-a trance isomerism derivative To. — vitamin A — is the cornerstone of the photochemical reactions happening in a retina of an eye (see. Rhodopsins ).

Vegetable products contain preferential p-carotene. At the higher plants most of all To. contain green leaves. The richest sources To. leaves of spinach (6 — 7 mg of % for dry weight) are. Cabbage lettuce contains 12,5 mg of %, and a sorrel — to 5 mg of % To. for wet weight. From root crops it is richest To. red carrots (6 — 25 mg of % for wet weight). It is a lot of To. contains in pumpkin: in Vitamin pumpkin of its 17,65 mg of % for wet weight.

In plants To. forms a complex with proteins which represent an important factor of chemical stabilization by K. Ferment oxidizing To. in plants, the lipoksidaaa is, apparently. Moisture of the cut-off plants and solar radiation destroy by K. Bystraya drying (e.g., lyophilic) and drying in a shadow, and also keep use of antioxidizers To. in plants. Among the bacteria synthesizing To., Mycobacterium phlei producing ai beta karotiny and some other carotinoids can be an example.

The highest animals, the person and, apparently, all invertebrates are deprived of ability to form K. U of some protests To. it is concentrated in eye spots. Tissues of animals usually contain a little To. However cows are capable to accumulate selectively p-carotene in a fatty tissue, in milk (apprx. 0,5 mg/l), concentration is especially high To. at cows in yellow (6 mg of %) and red (120 mg of %) bodies of ovaries.

At parenteral administration to the person To. does not turn into vitamin A and collapses. Its transformation into vitamin A in intestines depends on intake of fat and protein with food and existence of enough bile and an active lipase. Vitamins E and With and other natural antioxidants protect To. from destruction in intestines. To. it is non-toxical.

How to lay down. drug K. vitamin A is appointed according to the same indications, as (see. Retinolum ); at the same time it is considered that its activity is twice less, than vitamin A. With the advent of a large number of different forms of medicines of vitamin A the need for various drugs K decreased.


Bibliography: Leutsky K. M. Vitamin A, Chernivtsi, 1959.

K. M. Leutsky.

Яндекс.Метрика