vitamin A It is a class of compounds composed of β - ionone ring and Saturated monohydric alcohol The hydroxyl group of the active twenty carbon unsaturated hydrocarbon can be esterified or converted into aldehyde or acid, and can also exist as free alcohol. Vitamin A includes vitamin A one (Retinol) and vitamin A two (dehydroretinol). The difference between the two is that C in the violet ring of vitamin A2 three And C four There is a double bond between; The molecular formula of vitamin A is C twenty H thirty o， vitamin A two The molecular formula is C twenty H twenty-eight o。 [1] Vitamin A is insoluble in water, but soluble in fat and organic solvents. Vitamin A is a yellowish flake crystal with a melting point of 64 ℃ two Melting point 17~19 ℃, usually golden yellow oil, vitamin A one There are conjugated double bonds in the structure, belonging to isoprene There are many cis and trans stereoisomers. Vitamin A in food one It is mainly of all trans structure, with the highest bioavailability and vitamin A two Its biological potency is only vitamin A one 40%. Vitamin A mainly exists in the liver of animals, and retinol and its esters are the main forms. There is no vitamin A in plants and fungi, but there are Carotene After entering the human body, it can be metabolized into vitamin A and has vitamin A activity, which is usually called Pro vitamin A (The compounds in natural foods that can be converted into vitamins in the human body are called provitamins). Among the provitamin A, β - carotene has the highest conversion efficiency. One molecule of β - carotene can be converted into two molecules of vitamin A after hydrolysis. [1] Vitamin A is quite stable to heat in the absence of oxygen. It will not be damaged by general thermal processing methods, and will not decompose even if heated to 120~130 ℃. Vitamin A is relatively stable in alkaline and freezing environments, but unstable to acids. Heat treatment (such as cooking, tank storage and processing), light, acidification, hypochlorite or dilute iodine solution can convert all trans carotenoids into cis isomers, causing the loss of vitamin A activity. Because there are many unsaturated double bonds in the molecule, vitamin A and carotenoids are sensitive to oxygen, oxidants and lipoxygenase. High temperature, light (especially ultraviolet light) and metal ions can accelerate their oxidative decomposition. The oxidative degradation of vitamin A and carotenoids in food is similar to Unsaturated fatty acid The oxidative degradation of fat is caused by direct peroxidation or indirect free radicals produced in the process of fat oxidation. [1] 1. Enhance the participation of retinal photosensitivity Rhodopsin The synthesis of rhodopsin is reduced when lacking, and the sensitivity to weak light is reduced, and the vision is blurred under weak light, which is called night blindness. [2] 2. Maintain the integrity and function of epithelial tissue structure and participate in glycoprotein synthesis. In case of lack, it can cause epithelial dryness, hyperplasia and keratinization, such as sebaceous gland keratinization, and papules; Keratinization of lacrimal gland cells, reduction of tear secretion and dry eyes are called xerophthalmia. [2]
3. Promote the normal growth and development of the body, promote the differentiation of bone cells, and maintain Osteoblast and Osteoclast Balance between; Promote the synthesis of proteins, mucopolysaccharides and steroids, and tissue growth and development will be poor in case of lack. [2] 4. Others
promote Phagocyte and lymphocyte Function, promoting cell factor Release, enhance the immunity of the body; Effectively inhibit the activity of oxygen free radicals, protect cells from damage, and have certain cancer prevention effects. [2] vitamin D It is a class containing Cyclopentane phenanthrene Structural sterols. Six kinds of vitamin D have been identified, namely vitamin D two Vitamin D three Vitamin D four vitamin D five Vitamin D six And vitamin D seven , the most important of which is vitamin D two ( Ergocalciferol , gerocalciferol) and vitamin D three ( Cholecalciferol , cholecalciferol), their structures are very similar, vitamin D two Specific vitamin D three There is one more double bond and methyl group on the branch chain. vitamin D two The molecular formula is C twenty-eight H forty-four O， vitamin D three The molecular formula is C twenty-seven H forty-four O。 [1] Vitamin D is white crystal, insoluble in water, soluble in fat and organic solvents, odorless, tasteless, and has little impact on the color and flavor of food. Vitamin D only exists in animals, in the form of esters. Plants and yeast do not contain vitamin D, but Ergosterol It is converted into Vitamin D2 7-dehydrocholesterol in human and animal skin can be converted into vitamin D after ultraviolet irradiation three 。 [1] Vitamin D is very stable, general processing and storage conditions will not cause loss, vitamin D has strong heat resistance, and disinfection, boiling and autoclaving have no effect on its activity. Frozen storage also has little effect on vitamin D in milk and butter, but vitamin D will be rapidly damaged when exposed to light, oxygen and acid, and needs to be stored in airtight sealed containers. The photolysis mechanism of vitamin D may be direct Photochemical reaction Or the automatic oxidation of fat induced by light is indirectly involved in the reaction. Vitamin D is prone to oxidation mainly because there are unsaturated double bonds in the molecule. When the fat is oxidized and rancid, vitamin D in it will also be destroyed. Excess radiation of vitamin D can form a small amount of toxic compounds. [1] Vitamin D has no physiological activity and needs to be converted into 25 hydroxyvitamin D in the liver first two It is then converted into 1,25-dihydroxyvitamin D in the kidney to be active. Its main role is to participate in calcium and phosphorus metabolism: ① promote the absorption of calcium and phosphorus in the small intestine and renal tubules, and maintain normal and stable blood calcium and phosphorus concentrations. ② stay Parathyroid hormone With the cooperation of calcitonin, it can promote bone calcium into the blood and maintain the balance of blood calcium and phosphorus. ③ Promote calcium deposition in the new bone formation site, promote growth and bone calcification, and promote sound teeth. In case of deficiency, the absorption of calcium and phosphorus is reduced, showing hypocalcemia, hypophosphatemia, hand and foot convulsions and convulsions; The osteogenesis process is blocked, and even the bone salt is dissolved again, causing rickets in children and rickets in adults Osteomalacia 。 [2] Vitamin E is a kind of tocopherol and Tocotrienol (tocotrienols). Both tocopherol and tocotrienol are derivatives of 6-hydroxybenzodihydropyran. There are double bonds at 3 ', 7' and 11 'of the side chain of tocotrienol, and other parts are identical to the structure of tocotrienol. There are 8 kinds of vitamin E that have been confirmed. Their difference lies in the number and position of methyl groups in the ring structure. The most important one is the derivatives of 4 kinds of tocopherol, namely, a-tocopherol, β - tocopherol, γ - tocopherol δ - tocopherol. A-tocopherol naturally present in food biological activity Largest, the so-called vitamin E generally refers to a-tocopherol. [1] Vitamin E is a light yellow to yellowish brown viscous liquid, odorless, tasteless, insoluble in water, soluble in fat and organic solvents. Vitamin E is not easy to be destroyed by acid, alkali and heat, and is stable even when heated to 200 ℃ under anaerobic conditions; It is quite stable to white light, but sensitive to ultraviolet light. Its color gradually darkens, and it is sensitive to oxygen. It is easy to be oxidized to quinone structure and presents dark red 2+ 、Cu 2+ Etc.) can accelerate the oxidation reaction. [1]
Vitamin E is an excellent natural antioxidants , capture free radicals by providing phenol hydroxyl hydrogen protons and electrons. Unesterified a-tocopherol reacts with peroxide free radicals to generate hydroperoxides and relatively stable a-tocopherol free radicals. Tocopherol free radicals generate dimers or trimers through self polymerization, which stops the free radical chain reaction and prevents the automatic oxidation of unsaturated fatty acids. In meat curing, nitrite The synthesis of nitrosamines with amino substances is carried out through the free radical mechanism. Vitamin E can eliminate free radicals, thus preventing the formation of nitrosamines. The content of vitamin E in animal feed will affect the antioxidant capacity of slaughtered animal meat, thus affecting its eating quality. [1] 1. Antioxidation can inhibit the oxidation of unsaturated fatty acids and reduce Lipid peroxide It can prevent aging, cancer and prevent atherosclerosis effect. [2] 2. Maintain and promote reproductive function Gonadotropin Increase secretion, promote sperm production and movement, increase follicle growth and progesterone secretion. [2] 3. Participate in multiple enzyme activities to enhance microsome Mixed functional oxidase Activity, inhibition Deoxyribonucleic acid It can also protect sulfhydryl containing enzymes. [2] 4. Others maintain the normal permeability of capillaries, increase blood flow, repair scars after vascular wall damage, inhibit platelet aggregation, and prevent Thrombosis ； Maintain the normal structure and function of skeletal muscle, myocardium and smooth muscle. [2] vitamin K It is the general name of a series of 2-methyl-1,4-naphthoquinone derivatives. Natural vitamin K has vitamin K one (Phylloquinone) and vitamin K two (polyisopentenylmethylnaphthoquinone), vitamin K three (2-methyltheaquinone, menadione) is artificially synthesized. The difference between these derivatives is that they have or do not have terpenoid branched chains at position 3. vitamin K one The molecular formula is C thirty-one H forty-six O two , Vitamin K two The molecular formula is C forty-one H fifty-six O two , Vitamin K three The molecular formula is C forty-one H fifty-six O two 。 vitamin K one It mainly exists in plant tissue, vitamin K two It is a metabolite of many bacteria, vitamin K one and Vitamin K2 They are insoluble in water, soluble in fat and organic solvents, odorless or almost odorless. vitamin K one It is a yellow viscous oily liquid, and its alcohol solution can be crystallized when it is cooled. The melting point is - 20 ℃, and vitamin K two It is yellow crystal with melting point of 53.5~54.5 ℃. vitamin K three Easily soluble in water, yellow crystal, with activity higher than vitamin K one And vitamin K two High. [1] Vitamin K is quite stable to heat and insoluble in water, so it has little loss during normal food processing and cooking. Some reducing agents can reduce the naphthoquinone structure of vitamin K to hydroquinone structure, but they still have biological activity. Vitamin K is easily damaged by alkali, oxidant and light (especially ultraviolet light). Vitamin K is reductive and can quench free radicals (with β - carotene vitamin E The same) can protect other ingredients (such as lipids) in food from oxidation, and reduce the generation of nitrosamines during meat curing. [1] 1. It can promote the liver to synthesize four coagulation factors, prothrombin and transformation acceleration factor, Antihemophilic factor Promote blood coagulation. The prothrombin precursor in the liver has no coagulation effect. Only by transforming the precursor into prothrombin under the action of vitamin K can coagulation be promoted. In preventing Hemorrhagic disease of newborn , prevent internal bleeding and Hemorrhoid bleeding It plays an important role in reducing massive bleeding in women's physiological period and promoting normal blood coagulation. [3] 2. It can enhance intestinal peristalsis and secretion function, and delay Glucocorticoid It is decomposed in the liver and has the effect similar to hydrocortisone. Long term injection of vitamin K can enhance the endocrine activity of thyroid gland. [3] 3. It can relax visceral smooth muscle, relieve renal colic, biliary colic, and urinary bleeding. Its injection is often used clinically to treat hematuria, urinary stones, and gallstones, which can relieve spasm and pain. [3]
