Vitamin E Content and Composition in Tomato Fruits: Beneficial Roles and Bio-Fortification

Several epidemiological studies have demonstrated that high vitamin E intakes are related to a reduced risk of non-communicable diseases, while other dietary antioxidants are not, suggesting that vitamin E exerts specific healthy functions in addition to its antioxidant role. In this regard, tomato (Solanum lycopersicum), one of the most consumed vegetables of the whole world population, is an important source of both tocopherols and tocotrienols. However, vitamin E content may strongly depend on several biotic and abiotic factors. In this review we will debate the elements affecting the synthesis of tocopherols and tocotrienols in tomato fruit, such as environmental conditions, genotype, fruit maturity level, and the impact of classical processing methods, such as pasteurization and lyophilization on the amount of these compounds. In addition we will analyze the specific vitamin E mechanisms of action in humans and the consequent functional effects derived from its dietary intake. Finally, we will examine the currently available molecular techniques used to increase the content of vitamin E in tomato fruit, starting from the identification of genetic determinants and quantitative trait loci that control the accumulation of these metabolites.     

Tocopherols and Tocotrienols—Bioactive Dietary Compounds; What Is Certain,What Is Doubt?

Tocopherols and tocotrienols are natural compounds of plant origin, available in the nature. They are supplied in various amounts in a diet, mainly from vegetable oils, some oilseeds, and nuts. The main forms in the diet are α- and γ-tocopherol, due to the highest content in food products. Nevertheless, α-tocopherol is the main form of vitamin E with the highest tissue concentration. The α- forms of both tocopherols and tocotrienols are considered as the most metabolically active. Currently, research results indicate also a greater antioxidant potential of tocotrienols than tocopherols. Moreover, the biological role of vitamin E metabolites have received increasing interest. The aim of this review is to update the knowledge of tocopherol and tocotrienol bioactivity, with a particular focus on their bioavailability, distribution, and metabolism determinants in humans. Almost one hundred years after the start of research on α-tocopherol, its biological properties are still under investigation. For several decades, researchers’ interest in the biological importance of other forms of vitamin E has also been growing. Some of the functions, for instance the antioxidant functions of α- and γ-tocopherols, have been confirmed in humans, while others, such as the relationship with metabolic disorders, are still under investigation. Some studies, which analyzed the biological role and mechanisms of tocopherols and tocotrienols over the past few years described new and even unexpected cellular and molecular properties that will be the subject of future research.     

Tocopherol and tocotrienol composition of the seed lipids of a number of species representing the Bulgarian flora

The tocochromanols present in the seed lipids of representatives of the Bulgarian flora (mostly native wild plants and some introduced and/or cultivated plants) have been investigated. The content and composition of tocopherols and tocotrienols in the seed oils of 43 species belonging to 28 different plant families were determined. The results are discussed in view of their potential use as vitamin E concentrates and as sources of antioxidants for the preservation of food lipids.     

Enhancing Vitamin E in Oilseeds: Unraveling Tocopherol and Tocotrienol Biosynthesis

Naturally occurring vitamin E, comprised of four forms each of tocopherols and tocotrienols, are synthesized solely by photosynthetic organisms and function primarily as antioxidants. These different forms vary in their biological availability and in their physiological and chemical activities. Tocopherols and tocotrienols play important roles in the oxidative stability of vegetable oils and in the nutritional quality of crop plants for human and livestock diets. The isolation of genes for nearly all the steps in tocopherol and tocotrienol biosynthesis has facilitated efforts to alter metabolic flux through these pathways in plant cells. Herein we review the recent work done in the field, focusing on branch points and metabolic engineering to enhance and alter vitamin E content and composition in oilseed crops.     

Some compositional properties of seeds and oils of eightAmaranthus species

Grain of 21Amaranthus accessions (eight species) was analyzed for crude fat, fatty acid profiles (FAP), and vitamin E (tocopherols and tocotrienols). Contents of (1→3), (1→4) β-glucan were determined in 12 accessions (four species), and trypsin inhibitor activity (TIA) in 20 accessions (six species). FAP and vitamin E profiles were compared to those of barley, buckwheat, corn, lupin, oat, and wheat oils. Crude fat content ranged from 5.2 to 7.7%, and of the oils examined, amaranth oil was most similar in FAP to corn and buckwheat oils. Amaranth was higher than all but wheat and lupin in tocopherol content but was virtually devoid of tocotrienols, which have been shown to have hypocholesterolemic activity. Amaranth grain did not contain (1→3), (1→4) β-glucans and was low in trypsin inhibitor activity (≤4.3 trypsin units inhibited/mg). Any hypocholesterolemic effects of dietary amaranth are apparently due to substances other than (1→3), (1→4) β-glucans or tocotrienols.     

Distribution of tocopherols and tocotrienols to rat ocular tissues after topical ophthalmic administration

With increasing evidence suggesting the involvement of oxidative stress in various disorders and diseases, the role of antioxidants in vivo has received much attention. Chemically, tocopherols and tocotrienols are closely related; however, it has been observed that they have widely varying degrees of biological effectiveness. The present study has been carried out in an attempt to deepen our understanding of whether there is a significant difference in distribution between tocopherol and tocotrienol homologs to rat eye tissues. Rats were administered 5 μl of pure tocopherol or tocotrienol to each eye once a day for 4 d. Various tissues of the eyes were separated and analyzed for tocopherol and tocotrienol concentrations. The concentration of α-tocotrienol increased markedly in every tissue to which it was administered; however, no significant increase was observed in the case of α-tocopherol. The intraocular penetration of γ-tocopherol and γ-tocotrienol did not differ significantly. Additionally, a significant increase in total vitamin E concentration was observed in ocular tissues, including crystalline lens, neural retina, and eye cup, with topical administration using a relatively small amount (5 μL) of vitamin E, whereas no significant increase was observed when the same amount of vitamin E was administered orally. Topical administration of tocotrienols is thus an effective way to increase ocular tissue vitamin E concentration.     

Tocopherol and tocotrienol homologs in parenteral lipid emulsions

Parenteral lipid emulsions, which are made of oils from plant and fish sources, contain different types of tocopherols and tocotrienols (vitamin E homologs). The amount and types of vitamin E homologs in various lipid emulsions vary considerably and are not completely known. The objective of this analysis was to develop a quantitative method to determine levels of all vitamin E homologs in various lipid emulsions. An HPLC system was used to measure vitamin E homologs using a Pinnacle DB Silica normal phase column and an isocratic, n‐hexane:1,4 dioxane (98:2) mobile phase. An optimized protocol was used to report vitamin E homolog concentrations in soybean oil‐based (Intralipid®, Ivelip®, Lipofundin^® N, Liposyn^® III, and Liposyn^® II), medium‐ and long‐chain fatty acid‐based (Lipofundin^® , MCT and Structolipid®), olive oil‐based (ClinOleic® ), and fish oil‐based (Omegaven®) and mixture of these oils‐based (SMOFlipid®, Lipidem®) commercial parenteral lipid emulsions. Total content of all vitamin E homologs varied greatly between different emulsions, ranging from 57.9 to 383.9 µg/mL. Tocopherols (α, β, γ, δ) were the predominant vitamin E homologs for all emulsions, with tocotrienol content < 0.3%. In all of the soybean emulsions, except for Lipofundin® N, the predominant vitamin E homolog was γ‐tocopherol, which ranged from 57–156 µg/mL. ClinOleic® predominantly contained α‐tocopherol (32 µg/mL), whereas α‐tocopherol content in Omegaven® was higher than most of the other lipid emulsions (230 µg/mL). Practical applications: The information on the types and quantity of vitamin E homologs in various lipid emulsions will be extremely useful to physicians and healthcare personnel in selecting appropriate lipid emulsions that are exclusively used in patients with inadequate gastrointestinal function, including hospitalized and critically ill patients. Some emulsions may require vitamin E supplementation in order to meet minimal human requirements. Vitamin E homologs (tocopherols and tocotrienols) contain a chromanol ring and a hydrophobic side chain.     

Vitamin E in foods: Determination of tocols and tocotrienols

A method is described for the analysis of foods for the forms of vitamin E. Detailed procedures are given for extraction, saponification and partial purification by thin layer chromatography. The individual tocopherols (both tocols and tocotrienols) are identified and estimated as their trimethylsilyl ethers by gas liquid chromatography on SE-30 or Apiezon L at 235 C. Retention ratios are also given for separations on OV-17. Response factors relative to didecyl pimelate as an internal standard and overall recoveries were determined for α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol, β-tocotrienol and α-tocotrienol. Sample sizes depended on tocopherol content and were usually chosen to contain 3–50 μg of the individual tocopherols. Data for a number of seeds and oils are given. The greatest variety of forms was found in barley, which contains all the forms listed above, plus γ-tocotrienol.     

High performance liquid chromatography of the tocols in corn grain

A sensitive and selective method was developed for analyzing the tocol isomers in corn grain by high performance liquid chromatography (HPLC) with fluorescence detection. The relative proportions and the total amounts of the tocol isomers (α-tocopherol, α-tocotrienol, γ-tocopherol and γ-tocortrienol) varied greatly among the 15 corn inbreds that were examined. Although γ-tocopherol has traditionally been considered to be the predominant vitamin E isomer in corn, inbreds with equal or higher levels of α-tocopherol have been discovered. No tocotrienols were found in corn germ oil, only α-and γ-tocopherols. Analysis of the tocopherols of the germ oils of inbreds and their reciprocal crosses indicated that the proportions of the α- and γ-isomers and the total amount of the tocopherols are heritable. Presented at the 74th AOCS annual meeting, Chicago, 1983.     

Vitamin E und Haltbarkeit von Pflanzenölen

Vitamin E and stability of vegetable oils. The main occurrence of vitamin E basing on its synthesis and its lipophilic character are vegetable oils, seeds, nuts and cereals. The most important task of tocopherols are their antioxidative capacity in food lipids. The antioxidative potential of tocotrienols in comparison to their corresponding tocopherols is lower. According to the chemical structure γ- and δ-tocopherol are more effective than α-tocopherol. An improvement of the antioxidative capacity is possible by controlled adding to tocopherol compounds as well as by the use of synergists like ascorbylpalmitate. For this improvement the composition of fatty acids, the tocopherol content in native oil and the circumstances of the oxidation should always be considered.     

Dietary fat composition and tocopherol requirement: I. Lack of correlation between nutritional indices and results of in vitro peroxide hemolysis tests

In general, the native tocopherols in polyunsaturated vegetable oils such as cottonseed oil, corn oil and their lightly hydrogenated products include sufficient vitamin E for growth, reproduction, lactation and normal lipid metabolism in the rat. The administration of vitamin E to animals fed diets deficient in essential fatty acids (e.g., a hydrogenated coconut oil or a fat-free diet) does not stimulate growth or reproductive performance per se, although testes development in the male rats is improved and some improvement in lipid metabolism is also noted. Hemolysis of the erythrocytes in vitro by hydrogen peroxide is increased in animals on diets rich (30%) in polyunsaturated vegetable oils or on diets providing no essential fatty acids at all. However, the conditions of the in vitro hemolysis test are not related to those in vivo and the in vitro test is not a measure of erythrocyte fragility. In addition, the in vitro hemolysis test does not necessarily reflect plasma tocopherol levels nor an abnormal nutritional state as a result of subsistence on high linoleate, low tocopherol intake, but rather measures the susceptibility to oxidation of a labile biological substrate and indicates the effective balance between potentially oxidizable lipids (polyunsaturates) in the stroma of the red blood cell and the antioxidant present (tocopherol or vitamin E). The labile lipid substrate may be either of exogenous origin (diet) or may be formed endogenously through tissue synthesis (as a result of an essential fatty acid deficiency). It is concluded that the in vitro hemolysis test may not be a valid indicator of vitamin E nutriture unless it is used in conjunction with other nutritional tests.     

The chemistry and antioxidant properties of tocopherols and tocotrienols

This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action. Despite the general agreement that α-tocopherol is the most efficient antioxidant and vitamin E homologuein vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectivenessin vitro, especially when compared to γ-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherolsin vivo andin vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (α-, β-, γ-, and δ-) in relation to their interactions with the important chemical species involved in lipid peroxidation, specifically trace metal ions, singlet oxygen, nitrogen oxides, and antioxidant synergists. Although literature reports related to the chemistry of the tocotrienols are quite meager, they also were included in the discussion in virtue of their structural and functional resemblance to the tocopherols.     

Serum homocysteine, folate and vitamin B12 in venezuelan elderly

The anatomical and physiological changes of aging make elderly people a vulnerable group to malnutrition and specific deficiencies of nutrients such as vitamin B12 and folate. This study was aimed to establish relationships among serum vitamin B12, folate, homocysteine concentrations and dietary intake and adequacy. Fifty five male and female elderly (60 and more years), free-living, were assessed. Measurements were: serum vitamin B12 and folate by radioimmunoanalysis (RIA), homocysteine by polarized fluorescence immunoassay, nutrient intake by three 24 hours recalls and food frequency questionnaire. Nutritional status was determined by Body Mass Index (BMI). Serum vitamin B12 and folate were at normal range (423,3+/-227,6 pmol/l and 6,4 +/- 4,5 mg/ml), but 17,5% of elderly had B12 deficiency and 12% had folate deficiency. Serum homocysteine was higher than reference values (15,8+/-4,4 mmol/l), but 47,5% showed concentrations above 15 mmol/L, male population showed higher mean value (p: 0,01). Nutrient intake was inadequate by deficiency. BMI indicated 11,8% of undernutrition, 29,4% of overweight and 20,6% of obesity A negative and inverse correlation between homocysteine and serum folate was found. Results suggest a biochemical deficiency of B12 and folate that is expressed as elevated homocysteine levels. These finding represent a high cardiovascular risk factor for this elderly group.     

Simultaneous Determination of Retinol Esters and Tocochromanols in Foods Using Nitro-Column HPLC

All food components with vitamin A and E activity, i.e. all-trans retinol. its cis isomers and their esters as well as the four tocopherols. the four tocotrienols, and α-tocopheryl acetate, were separated by HPLC using a nitro-column and a three-step gradient elution with n-hexane and terα-butylmethylether mixtures. β-carotene and the retinol isomers were determined with an UV/Vis detector, all other compounds with a fluorescence detector connected in series. Fats, oils, and lipid extracts from foods can he injected onto the HPLC column without any clean-up.     

Supplementation of tocotrienol‐rich fraction increases interferon‐gamma production in ovalbumin‐immunized mice

Palm oil is a rich source of vitamin E. The tocotrienol‐rich fraction (TRF) extracted from palm oil contain 70% tocotrienols and 30% tocopherols. The effect of TRF supplementation on the immune modulation was evaluated in 6‐wk‐old female BALB/c mice immunized with ovalbumin (OVA) adjuvanted with alum. Mice in control and experimental groups were immunized subcutaneously (s.c.) on days 14 and 28 with a single dose of 50 µg OVA. The mice in the experimental group were orally gavaged daily with 1 mg of TRF from palm oil while those in the control group received carrier oil. The results show that mice in the experimental group produced significantly (p<0.05) higher levels of interferon‐gamma (IFN‐γ) compared to the control group. There was no significant (p>0.05) difference in the levels of interleukin‐4 (IL‐4) produced between the control and experimental animals. Lymphocyte proliferation in response to mitogen or OVA stimulation was significantly (p<0.05) higher in splenocytes derived from the TRF supplemented mice compared to control mice. These findings show that daily supplementation of palm TRF can induce a strong cell‐mediated immune response, i.e., T‐helper‐1 (Th1) response, which would be beneficial to fight viral infections and cancer.     

Comparison of serum concentration and dietary intake of alpha-tocopherol in a sample of urban and rural Costa Rican adolescents

Results from several studies have suggested that vitamin E intake could inhibit the progression of atherosclerotic lesions. Therefore, this study was designed to evaluate Costa Rican adolescents' serum alpha-tocopherol levels and their correlation with Body Mass Index (BMI) and the dietary intake of vitamin E and saturated and polyunsaturated fat. Ninety-five healthy, non-smoking adolescents and non-vitamin supplement users (aged 13-18) from urban and rural areas in San José, Costa Rica, were included in this study. Serum levels of lipid adjusted alpha-tocopherol were significantly higher in rural adolescents compared with urban youngsters (4.192 mumol/mmol +/- 0.831 and 3.486 mumol/mmol +/- 0.996, respectively). Likewise, reported mean daily 1000 kcal adjusted-vitamin E intake was higher in rural adolescents than in urban youngsters (9.2 +/- 3.7 mg. 16.0 +/- 8.7 mg). An important correlation was observed between intake of energy from saturated fat and adjusted-alpha-tocopherol serum levels (r = 0.430). Contrariwise, they correlated poorly with dietary alpha-tocopherol (r = 0.273), suggesting that serum is not a good biomarket of intake for alpha-tocopherol. Additionally, our results showed a negative relationship between BMI and adjusted-serum vitamin E levels (beta = 0.189; CI 95% -0.153, -0.013). The analysis of vitamin E intake showed that over 25% of adolescents have inadequate intake of the nutrient. This study suggests that nutritionists and pediatricians should encourage alpha-tocopherol intake and monitor the food sources of the nutrient and the adolescents' body weight as part of the strategies aimed at developing a healthy lifestyle.     

The nutritional reputation of palm oil

The high saturated fatty acid content of palm oil and hence its potential to raise circulating levels of cholesterol has given this tropical oil a bad nutritional reputation. Three considerations suggest that this reputation may soon need to be re‐evaluated. First, the need of the edible oil industry to find alternatives to partially hydrogenated oils has led to the reintroduction of palm oil. What evidence there is suggests that replacement of partially hydrogenated oils with palm oil leads to a rise in HDL‐cholesterol levels an effect which would be expected to lead to a fall in the risk of developing heart disease. Second, palm oil is a very rich source of tocotrienols the neglected part of the vitamin E complex. If beneficial effects of tocotrienols on health were to be demonstrated then this would inevitably improve the nutritional reputation of palm oil. Third, red palm oil is the richest and most available vegetable source of provitamin A carotenoids known and it has been shown that this oil can improve vitamin A status in populations which are deficient in this vitamin.     

Vergleich der Vitamin- und Antioxidans-Wirkung der verschiedenen Tocopherole bei den wichtigsten Pflanzenölen

Comparison of Vitamin Activity and Antioxidant Activity of Various Tocopherols from Important Vegetable Oils Unsaponifiables of most vegetable oils contain tocopherols in varying amounts and ratios. All these tocopherols do not have the same action. It is known that vitamin E activity is in the decreasing order for α-, β-, γ- and δ-tocopherols whereas antioxidant activity increases in the same order. Accordingly, an oil which is rich in vitamin E is not necessarily the most stable one. The tocopherols occuring most commonly are α- and γ-tocopherols. Influence of various refining steps on the tocopherol content is discussed briefly.     

Characterization of Oil Extracted from Buriti Fruit (Mauritia flexuosa) Grown in the Brazilian Amazon Region

Five samples of buriti oil from industrial and artisanal suppliers were characterized in terms of nutritional quality parameters (nutraceutical levels) and acidity. As a first screening, each sample was analyzed by titration, spectrophotometry and an HPLC method, and the results were compared. As expected, artisanal samples showed lower acidity and higher levels of carotenes and tocols (tocopherols and tocotrienols). A blend of industrial and artisanal samples in suitable proportions was completely characterized in terms of analytical and physico-chemical properties, i.e., fatty acid composition, iodine value, partial and total acylglycerol contents, refractive index (40 °C), saponification value, unsaponifiable matter, acidity (expressed as % of oleic acid), peroxide value, phosphorus content, oil stability index, tocol and carotene concentrations. The results of the present study showed that buriti oil is a valuable source of monounsaturated fatty acids, and vitamins A and E. No previous work in the literature has analyzed buriti oil to this extent. The chromatographic method using HPLC was effective in qualifying and quantifying tocopherols, tocotrienols and carotenes.