BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 8. VITAMINS

8.2. Fat-soluble vitamins

8.2.4. Vitamin E group

Structure and physicochemical properties. The fat-soluble vitamin tocopherol, essential for fetal development in rats, was discovered in 1922. Tocopherols belong to chroman derivatives containing an isoprene chain at position 2. In nature, there are A number of such compounds that differ in the arrangement of methyl groups in the chroman ring, the degree of methylation, and the saturation level of the side chain.

Several natural compounds with vitamin activity are known: α-tocopherol (5,7,8-trimethyltocol), β-tocopherol (5,8-dimethyltocol), γ-tocopherol (7,8-dimethyltocol), δ-tocopherol (8-methyltocol), and several others. The most active is α-tocopherol (Fig. 8.6).

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Fig. 8.6. α-tocopherol (5,7,8-trimethyltocol)

Derivatives with a shorter hydrocarbon chain and unsaturated ones (tocotrienols) also exhibit biological activity. Tocopherols are light-yellow or colorless oily substances. The vitamin is thermostable. Its synthesis occurs exclusively in plants, since The formation of the hydroquinone ring is associated with the METABOLISM of aromatic Amino Acids, which are not synthesized in the animal Organism.

Biochemical Functions. Tocopherols are part of the body's antioxidant defense system against the damaging effects of reactive, free-radical oxygen species and serve as the primary natural fat-soluble antioxidants. It inhibits free-radical reactions within The Cell, thereby preventing the chain reactions of Lipid Peroxidation of Unsaturated Fatty acids in Membrane Lipids. The vitamin is capable of redox transformations. Tocopherols are also able to integrate into the cell membranes of adipose tissue, Liver, and skeletal Muscles.

Requirement and natural occurrence. Tocopherol was discovered as an active substance that prevents Infertility. Rats kept on an artificial diet supplemented only with B-group Vitamins developed infertility. In females, the Placenta was affected, while in males, gonadal atrophy was observed. Females retained The ability to conceive, but normal fetal development ceased after 8-12 days, resulting in embryonic death. In addition, muscular dystrophy was observed, accompanied by a decrease in Muscle levels of Myosin, Glycogen, creatine, potassium, manganese, and phosphates, as well as fatty liver infiltration.

Vitamin deficiency may occur when consuming a predominantly carbohydrate-rich diet with a low fat content. Absorption in the Small Intestine occurs only in the presence of Bile acids and fats. The normal concentration of tocopherols in human Blood Plasma is 0.8-1.5 mg/dL.

The main dietary sources of vitamin E for humans are vegetable oils, as well as lettuce, sprouted grains, and peas. The daily requirement depends on the physiological state of the organism and diet, averaging approximately 5-15 mg.