Chemical and physical properties of vitamin E

Vitamin E is the major lipid-soluble component in the cell antioxidant defence system and is exclusively obtained from the diet. The tocopherols are viscous oils at room temperature, insoluble in water but soluble in ethanol and aprotic solvents. Vitamin E is a slightly yellow to amber, practically odorless and tasteless, clear, viscous oil, which darkens on exposure to air or light by oxidation.

Vitamin E is a generic term denoting eight different isomers among which α-tocopherol is the most important and most active.

The melting point of RRR-α-tocopherol is 3 °C. The optical rotations of tocopherols are very small and depend on the nature of the solvent. RRR-α-tocopherol (RRR-α-T), is known to be more bioactive than all-rac-α-tocopherol (all-rac-α-T), a synthetic racemic mixture of 8 stereoisomers.

Tocopherols are easily oxidized and can be destroyed by peroxides ozone and permanganate in a process catalyzed by light and accelerated by polyunsaturated fatty acids and metal salts.

The ultraviolet absorption spectra of tocopherols and tocotrienols in ethanol show an absorption maximum at 292–298 nm, while the infrared spectra show OH (2.8 ± 3.0 µm) and CH (3.4 ± 3.5 µm) stretching and a characteristic band at 8.6 µm.

Vitamin E is a fat-soluble vitamin that consists of a group of tocols and tocotrienols with hydrophobic character, but possessing a hydroxyl substituent that confers an amphipathic character on them.

The interactions between vitamin E and water are hydrophobic in nature; hence, vitamin E is found to be insoluble in water since vitamin E is non-polar and water is polar in nature. Solubility is reported for α-tocopherol in aqueous mixtures containing ethanol at 33 °C. It has very low solubility in pure water owing to hydrophobic repulsion.

α-Tocopherol is fluorescent with an emission maximum about 325 nm in a hydrophobic solution. The bond dissociation energy of α-tocopherol's O–H bond is 77.1 kcal mol−1.31 The pKa values for α-, β-, γ-, and δ-tocopherol in a micellar solution were reported as 13.1, 12.8, 12.7, and 12.6 respectively.

The α-tocopherol are unstable to air and light, particularly when in alkaline media. α-tocopherol acid succinate is insoluble in water, slightly soluble in alkaline solutions, soluble in alcohol, in ether, in acetone and in vegetable oils; very soluble in chloroform.

The partition coefficient of α-tocopherol is 12.2, while that for ascorbic acid is −1.85,30 showing their lipophilic and hydrophilic characters, respectively.
Chemical and physical properties of vitamin E

Tocopherol losses in food

Naturally occurring vitamin E comprises tocopherols and tocotrienols. Processing and storage of foods can result in substantial tocopherol losses. Cooking of porridges of rolled oats and rye meal implies only minor effects on their tocopherol and tocotrienols contents.

Studies of alpha-tocopherol in UHT processed milk suggest that the processing conditions affect the subsequent losses, but that in all cases increased storage temperature led to increased rate of loss.

There was a loss of tocopherol reported in the study of potato chips. After only two weeks’ storage of the chips at room temperature, nearly half of the tocopherol was lost.

The losses were only slightly smaller during storage at freezer temperature.

Deep fat frying of fresh vegetable oil causes losses of about 10% but storage of fried foods, even at low temperature, may cause large losses.  The low content of alpha-tocopherol in frozen foods is surprising and indicates serious degradation even at 12 °C.

Boling of vegetables in water for up 30 minutes results in only minor losses of tocopherol.

Baking of white bread (200 °C, 30 minutes) destroyed of about 5% of the tocopherol in the crumb.

Tocopherol losses during microwave cooking are mainly caused by the effect of high temperature and not by microwaves as such. When sunflower oil was subjected to microwaves discontinuously for 120 min at two constant temperatures: namely 170 °C and less than 40 °C, tocopherol losses were 72% and 21%, respectively.
Tocopherol losses in food

Tocotrienols in palm oil

Vitamin E is one of the major essential vitamins. Since vitamin E is an essential nutrient for protecting the bio-membrane from oxidative damage, people have to take in sufficient amounts of vitamin E to maintain and promote nutritional health.

Vitamin E consists of two subgroups called tocopherols and tocotrienols. Tocotrienols are less common and belong to the vitamin E family and are potent lipid antioxidant. In foods, in which they occur, they are generally only found in small amounts.

Tocotrienols have become a focus of research in recent years because of new findings showing their high efficacy in protecting against heart-related diseases, including lowering of cholesterol and against certain cancers.

The sources with the largest amount of tocotrienols include wheat, barley, rice and most abundantly, the fruit of the palm from which palm oil is extracted.

Palm oil is by far the richest source of tocotrienols.

Palm oil is unique because it contains both tocotrienols and tocopherols unlike other vegetable oils some of which contain mainly alpha-tocopherol as the major tocopherol component.

The tumor protective effect of tocotrienols form palm oil was demonstrated by Komiyama and Yamoka (1993), Nesaretnam (1995), Guthrie (1997) and others.

The vitamin E fraction of palm oil, which is rich in tocotrienols, appears to be important in reducing certain tumors because palm oil stripped of the vitamin E does increase tumor yields.
Tocotrienols in palm oil

Selenium and vitamin E complementary roles

Selenium’s principal function is to inhibit the oxidation of lipids (fats) as a component of the intracellular enzymes glutathione peroxidase.

It is a vital antioxidant, especially when combined with vitamin E. It protects the immune system by preventing the formation of free radicals and destroys lipid peroxides that form and are released into cells.

Oxidation is the metabolic process by which fats, carbohydrates and preteens are converted to carbon dioxide, water and energy, burned to produce the energy needed for body functions.

However, oxidation of the body’s structural and functional component is harmful. The body must have a antioxidant defense mechanism to protect it from oxidation-induced damage. Selenium have a closely associated with vitamin E in its mode of function as a major component of this mechanism.

Glutathione peroxides occurs mainly in the cytosol and reduces peroxides before they can attack cell membranes, whereas vitamin E acts within the membrane itself as a second line of defense.

Selenium deficiency and vitamin E deficiency are so interrelated that it is usual to refer to the diverse group of disorders ascribed to their deficiencies as vitamin E-selenium deficiency.
Selenium and vitamin E complementary roles

Vitamin E Sources and Functions

It was discovered in 1922 in vegetable oil given the name ‘tocopherol’. Vitamin E, of which there are four different forms, is fat soluble.

The four have the same name except with the prefixes alpha-, beta-, gamma-, and delta-, (the first four letters of the Greek alphabet).

Only alpha-tocopherol contributes toward meeting the human vitamin E requirement and it is the most common form of vitamin E in food.

It is our body’s major fat soluble antioxidant. It protects vulnerable polyunsaturated lipids in cell membranes, in blood and elsewhere throughout the body.

The richest dietary sources of vitamin E are the vegetable oils. Safflower and olive oil contain the highest proportion of alpha-tocopherol, followed by soybean oil.

Curiously enough, these oils are also the richest sources of polyunsaturated fatty acids, which vitamin E protects from oxidation.

Nuts and seeds such as sunflower seeds, are among the best food sources.

In western diet, vitamins E intake derives mainly from fats and oils contained in margarine, mayonnaise, salad dressing and desserts, and increasingly also from fortified food (e.g., breakfast cereals, milk, fruit juices).

Vitamin E helps reduce oxidation of lipid membranes and the unsaturated fatty acids and prevents the breakdown of other nutrients by oxygen.

Some scientists compare the function of vitamin E on the cell membrane to a lightening and nullifying the damage that occurs of lightening strikes. This function of vitamin E is also performed and enhanced by other antioxidants, such as vitamin C, beta-carotene, glutathione (L-cysteine), coenzyme Q and the mineral selenium.

In fact, there is a direct recycling process for vitamin E that requires the immediate presence of beta-carotene, vitamin C, flavonoids, and coenzyme Q to work.

Observational studies have suggested that high intake of antioxidant including vitamins E, may lower the risk of some chronic disease, especially heart disease.

Different forms of vitamin E, other than alpha-tocopherol, have immuno-regulatory functions,

Alpha-tocopherol is the most common form of vitamin E in plasma and tissues and the most extensively studied for its beneficial effect on immune function, probably because it is the exclusively component in most vitamin E supplements.
Vitamin E Sources and Functions

Vitamin E Deficiency

Vitamin E was discovered in 1922, but not until 1983 that vitamin E was demonstrated to be dietary essential for human beings.

Vitamin E deficiency was first describe in children with fat malabsorption syndromes, principally abetalipoproteinemia, cystic fibrosis, and cholestatic liver disease.

They have been reports of vitamin E deficiency symptoms in person with protein calories malnutrition.

The frequency of human vitamin E deficiency is very rare, deficiency is usually associated with disease of fat malababsorption such as cystic fibrosis.

In individual at risk, it is clear that vitamin E supplements should be recommended to prevent deficiency symptoms.

Without vitamin E, the red blood cells break open and spill their contents, probably due to oxidation of the polyunsaturated fatty acids in their membranes.

The classic sign of vitamins E deficiency, known as erythrocyte hemolysis, is seen in premature infants, born before the transfer of vitamin E from the mother to the infant that takes place in the last week of pregnancy.

The primary human vitamin E deficiency symptoms is a peripheral neuropathy characterized by the degeneration of the large caliber axons in the sensory neurons.

Other vitamin E deficiency symptoms observed in humans include spinocerebellar ataxia, skeletal myopathy, and pigmented retinopathy.

Prolonged vitamin E deficiency also can causes neuromuscular dysfunction involving the spinal cord and retina of the eye.
Vitamin E Deficiency

Vitamin E

Vitamin E is present in human tissues and it is necessary for normal metabolism. It is found to be widely distributed in foods.

Much of the vitamin E in the diet comes from vegetable oils and products made from them, such as margarine and salad dressings. Wheat germ oil is especially rich in vitamin E.

The name originated in the early 192ss, Evans and Scoot Bishop describe a ‘substance X’ present in getable oil that was essential to maintain rat fertility.

Deficiency of vitamin E in man has not been reported and so there is no recommended daily intake.

Vitamin E, however plays an important role in the body as an antioxidant by protecting substances such as unsaturated fatty acids, carotene and ascorbic acid, which are easily oxidized.

Vitamin E is an essentially naturally occurring fat-soluble nutrient that is involved in several biological processes such as immunity, protection against tissue damage (hear, nerve, etc) reproduction, growth and development.

One of the few generally recognized uses for vitamin E is in the treatment of hemolytic anemia in premature babies.

There were also a studies indicate that vitamin E may slow the aging process and prevent premature aging by prolonging the useful life of our cells, thus maintaining the function of our organs.
Vitamin E

Vitamin E and Cancer

The essentiality of vitamin E for humans was recognized in the late 1960s in connection with studies on premature infants in which hemolytic anemia was associated with vitamin E deficiency.

Vitamin E is considered to be most effective antioxidant more effective, for example, than beta carotene at relatively higher oxygen partial pressure, and is more selectively distributed to the nuclear fraction as compared with other sub-cellular fractions.

The fact that that high dosage of vitamin E is not toxic, therefore many research is focused on anti-cancerous properties of vitamin E.

The later study being made is the relation of vitamin E to the new growth, or division, of cells necessary to keep the tissues in healthy repair.

In one study, when cancer tissue was placed in a vitamin-E-rich blood serum, the cancer tissue did not grow. When a blood serum lacking vitamin E as used in a similar test, the cancer cells divide normally in the presence of vitamin E.

Many studies have also found that high levels of vitamin E in the body are associated with a lower risk of cancer, whereas low level are associated with a greater risk.

These trends have been indentified with breast cancer, cervical cancer and cervical dysplasia, colon cancer, lung cancer, and throat cancer.
Vitamin E and Cancer

Vitamin E

Vitamin E
Vitamin E, of which there are four different forms (the tocopherols), is fat soluble.

The four have the same name except with the prefixes alpha-, beta-, gamma-, and delta-, ( the first four letters of the Greek alphabet). The four compounds are closely related, with some difference in the molecular weight and in the position and number of certain molecular constituents.

This vitamin is an antioxidant that serves to prevent the oxidation of some body components, such as unsaturated fatty acids, and is necessary for reproduction.

Almost all foods contain some vitamin E, although corn oil, cottonseed oil, margarine, and peanut oil are especially good sources of this vitamin.

While the symptoms for vitamin E deficiency in humans are not clearly established , experiments with various animals have shown that vitamin E deficiency has an adverse effect on reproduction with apparent irreversible injury to the germinal epithelium.

Other symptoms noted in animal studies include injury to the central nervous system, growth retardation, muscular dystrophy, and interference with normal heart action.
Vitamin E

Vitamin E and Palm Oil

Vitamin E and Palm Oil
Palm oil is a good source of Vitamin E. A fat-soluble vitamin, Vitamin E is an essential micronutrient for humans and consists of two series of compounds - tocopherols and tocotrienols.

Both are characterized by a side chain which is saturated in the tocopherols , but unsaturated in the tocotrienols.

Although tocopherols occur in several vegetable oils, palm oil represents one of the richest, natural sources of tocotrienols, which are also present in rice bran and barley.

The Vitamin E in palm oil is a mixture of different tocopherols (18-22%) and tocotrienols (78-82%). Alpha and gamma tocopherol each account for about 35% of total tocopherols, while gamma tocopherol accounts for about 10%.

Amongst the tocotrienols, the major ones are gamma tocotrienol (46%), alpha tocotrienol (22%) and delta tocotrienol (12%).

Recently, palm oil-derived tocotrienols have been extensively studied for their antioxidant capabilities, anti-cancer properties (for which there is strong supportive scientific evidence), as well as their ability to influence cholesterol metabolism.

Although some of the earlier studies suggested that supplementation with tocotrienols lowered cholesterol by affecting endogenous synthesis, a recent study noted no effect. This may in part be due to the fact that it is not yet resolved which of the tocotrienol isomers are involved.
Vitamin E and Palm Oil

Vitamin E

Vitamin E
Vitamin E is a fat-soluble vitamin that exists in eight different forms. Each form has its own biological activity, the measure of potency or functional use in the body.

Alpha-tocopherol is the most active form of vitamin E in humans, and is a powerful biological antioxidant.

Antioxidants such as vitamin E act to protect your cells against the effects of free radicals, which are potentially damaging by-products of the body's metabolism.

Free radicals can cause cell damage that may contribute to the development of cardiovascular disease and cancer. Studies are underway to determine whether vitamin E might help prevent or delay the development of those chronic diseases.

Vegetable oils, nuts, and green leafy vegetables are the main dietary sources of vitamin E. Fortified cereals are also an important source of vitamin E in the United States.

Vitamin E