Comparison of geranylgeranyl and phytyl substituted methylquinols in the tocopherol synthesis of spinach chloroplasts

Geranylgeranyl substituted methylquinols are shown to be precursors of tocopherol biosynthesis in spinach chloroplasts as well as phytyl substituted ones. The geranylgeranyl substituted quinols are methylated even to a greater extent than the phytyl substituted ones. The connection to the so far known biosynthetic origin of -tocopherol is probably -tocotrienol which is hydrogenated to γ-tocopherol and then further methylated to -tocopherol

α-Tocopherol in plasma and milk from organically managed dairy cows fed natural or synthetic vitamin E or seaweed

The objective was to compare the effects of supplementing lactating dairy cows with synthetic (All-rac), natural (RRR) α-tocopheryl acetate or seaweed with a control on the concentration of α-tocopherol in blood and milk. Twenty four dairy cows in mid lactation, fed an organic feed ration, were randomly allocated to the four treatments in a replicated Latin square design. Plasma and milk α-tocopherol concentrations were higher in RRR and All-rac than in the other treatments and higher in RRR than in All-rac. RRR-α-tocopherol was the predominant steroisomer (> 86%), in both plasma and milk, whereas the remaining part was largely made up by the three synthetic 2R isomers. In cows fed the control, seaweed and RRR, the proportion of RRR-α-tocopherol in plasma and milk constituted more than 97% of the total α-tocopherol. The study demonstrated that dairy cows in mid and late lactation have preferential uptake of RRR-α-tocopherol compared to other stereoisomer

2-Methyl-6-phytylquinol and 2,3-dimethyl-5-phytylquinol as precursors of tocopherol synthesis in spinach chloroplasts

The incorporation of [Me-14C] from SAM-[Me-14C] into precursors indicates the following sequence of tocopherol synthesis in spinach: 2-methyl-6-phytylquinol (6-phytyltoluquinol) (1a) → 2,3-dimethyl-5-phytylquinol (phytylplastoquinol) (2a)→,γ-tocopherol (5a)→-tocopherol (6). 1a is particularly preferred to 2-methyl-5-phytylquinol (1b) and 2-methyl-3-phytylquinol (1c). 1a only forms 2a. 2a is converted to 6 via 5a and, to a lesser extent, 2,5-dimethyl-6-phylquinol (2b) to 6 via β-tocopherol (5b). Trimethylphytylquinol (3) is not an intermediate in the formation of 6. All reactions are independent of light

Tocopherol and plastoquinone synthesis in spinach chloroplasts subfractions

Subfractions isolated from intact purified spinach chloroplasts are able to prenylate the aromatic moiety of -tocopherol and plastoquinone-9 precursors. The biosynthesis of -tocopherol and plastoquinone-9 is a compartmentalized process. The chloroplast envelope membranes are the only site of the enzymatic prenylation in -tocopherol synthesis whereas the thylakoid membrane is also involved in the prenylation and methylation sequence of plastoquinone-9 biosynthesis. A very active kinase which forms phytyl-PP is localized in the stroma. Phytol but not geranylgeraniol is the polyprenol precursor of the side chain of -tocopherol in spinach chloroplasts

Assessment of vitamin E status in patients with systemic inflammatory response syndrome: plasma, plasma corrected for lipids or red blood cell measurements?

<b>Background:</b> There is some evidence that the plasma vitamin E status is perturbed as part of systemic inflammatory response and correcting this with other plasma markers may not lead to reliable results. The aim of the present study was to examine the longitudinal inter-relationships between plasma and red blood cell vitamin α-tocopherol in patients with systemic inflammatory response syndrome. <b>Methods:</b> α-tocopherol concentrations were measured, by HPLC, in plasma and red blood cells in normal subjects (n = 67) and in critically ill patients with systemic inflammatory response syndrome (n = 82) on admission and on follow-up. <b>Results:</b> Plasma α-tocopherol was significantly lower in the critically ill patients compared with the controls (all p < 0.001) with 41% of patients having concentrations below the 95% confidence interval. In contrast, when corrected for cholesterol, α-tocopherol concentrations were significantly higher in the critically ill patients compared with the control group (p < 0.001, 27% above the 95% confidence interval) and when corrected for triglycerides, α-tocopherol concentrations were significantly lower in the critically ill patients compared with the control group (p < 0.001). Red blood cell α-tocopherol corrected for haemoglobin was similar (p = 0.852) in the critically ill patients compared with control subjects. The longitudinal measurements (n = 53) gave similar results. <b>Conclusions:</b> These results indicate that there is a discrepancy between vitamin E measurements in plasma, in plasma corrected for lipids and in red blood cells. Although the value of correcting vitamin E concentrations by lipids is well established in population studies, the present study indicates that such correction is unreliable in the presence of systemic inflammatory response syndrome and that vitamin E status should be assessed using red blood cell α-tocopherol measurement

Influence of soy protein’s structural modifications on their microencapsulation properties: a-tocopherol microparticles preparation

Enzymatic and chemical modifications of soy protein isolate (SPI) were studied in order to improve SPI properties for their use as wall material for a-tocopherol microencapsulation by spray-drying. The structural modifications of SPI by enzymatic hydrolysis and/or N-acylation were carried out in aqueous media without any use of organic solvent neither surfactant. Emulsions from aqueous solutions of native or modified SPI and hydrophobic a-tocopherol, were prepared and spray-dried to produce a-tocopherol microparticles. The effect of protein modifications and the influence of the core/shell ratio on both emulsions and microparticles properties were characterised. The obtained results demonstrated that oil-in-water emulsions prepared with modified proteins had lower droplet size (0.5-0.9 μm) and viscosity (3.6-14.8 mPa×s) compared to those prepared with native proteins (1.1 μm and 15.0 mPa×s respectively). Efficiency of oil retention decreased after protein hydrolysis from 79.7 to 38.9%, but the grafting of hydrophobic chain by acylation improved efficiency of a-tocopherol retention up to 94.8%. Moreover, higher emulsion viscosity, particle size and process efficiency were observed with the increase of a-tocopherol amount

NIRS potential use for the determination of natural resources quality from dehesa (acorn and grass) in Montanera system for Iberian pigs.

NIRS technology has been used as an alternative to conventional methods to determinate the content of nutrients of acorns and grass from dehesa ecosystem. Dry matter (DM), crude fat (CF), crude protein (CP), starch, total phenolic compounds (TP), α-tocopherol, γ-tocopherol, fatty acids, neutral detergent fiber (NDF), total antioxidant activity (TAA) and total energy (TE) were determined by conventional methods for later development of NIRS predictive equations. The NIR spectrum of each sample was collected and for all studied parameters, a predictive model was obtained and external validated. Good prediction equations were obtained for moisture, crude fat, crude protein, total energy and γ-tocopherol in acorns samples, with high coefficients of correlation (1-VR) and low standard error of prediction (SEP) (1-VR=0.81, SEP=2.62; 1-VR=0.92, SEP=0.54; 1-VR=0.86, SEP=0.47; 1-VR=0.84, SEP=0.2; 1-VR=0.88, SEP=5.4, respectively) and crude protein, NDF, α-tocopherol and linolenic acid content in grass samples (1-VR=0.9, SEP=1.99; 1-VR=0.87, SEP=4.13; 1-VR=0.76, SEP=10.9; 1-VR=0.82, SEP=0.6, respectively). Therefore, these prediction models could be used to determinate the nutritional composition of Montanera natural resources

Contents of α-tocopherol and β-carotene in grasses and legumes harvested at different maturities

Concentrations of α-tocopherol and β-carotene in forage species at various maturities were studied in Scandinavia. Red clover (RC)/timothy (TI), RC/meadow fescue (MF), and birdsfoot trefoil (BT)/TI mixtures were grown in Skara and Umeå, Sweden. RC/TI,RC/perennial ryegrass (PR), white clover/PR and BT/TI were grown in Foulum, Denmark. Forages in Sweden were cut one week before heading (BH), at heading and one week after heading of TI. The regrowth was cut six and eight weeks after each harvest in the spring growth cycle. In Denmark, one first harvest and three regrowths were taken. Results from Skara and Foulum are presented. Highest concentrations of α-tocopherol and β-carotene (mg kg-1 DM) in legumes were found in BT grown in Skara (49.8 and 69.6 in spring growth cycle,48.1 and 79.8 in regrowth) and in Foulum (81.3 and 89.2). MF had more α-tocopherol and β-carotene than TI in the spring growth cycle (73.5 and 54.2 vs. 46.9 and 43.0 mg kg-1 DM). Highest concentrations of vitamins in the regrowth were found six weeks after BH with 71.8 and 104.8 mg α-tocopherol and 99.6 and 73.1 mg β-carotene kg-1 DM in legumes and grasses,respectively

Oxidative stress stimulates alpha-tocopherol transfer protein in human trophoblast tumor cells BeWo

alpha-Tocopherol transfer protein (alpha-TTP) has been identified as the major intracellular transport protein for the antioxidant vitamin E (alpha-Tocopherol). Expression of alpha-TTP on the reproductive system has been described both in mouse uterus and lately in the human placenta. The aim of this study was to clarify if placental expression of alpha-TTP can be modified by substances causing oxidative reactions. The human choriocarcinoma cell line BeWo was, therefore, treated with two known pro-oxidants. alpha-TTP expression was determined with immunocytochemistry and evaluated by applying a semiquantitative score. The presence of pro-oxidants in BeWo cells induced alpha-TTP expression. We thus hypothesize that stimulation of alpha-TTP expression by oxidative stress, as this was induced by pro-oxidants, could be part of an antioxidant process occurring in the placenta in the aim of enhancing the supply of alpha-Tocopherol. This process could occur both in normal pregnancies, as well as in pregnancy disorders presented with intensified oxidative stress. In that view, this model is proposed for further oxidative stress studies on trophoblast and placenta, on the grounds of clarifying the role of alpha-Tocopherol in pregnancy physiology and pathophysiology

Localization and synthesis of prenylquinones in isolated outer and inner envelope membranes from spinach chloroplasts

The prenylquinone content and biosynthetic capabilities of membrane fractions enriched in outer and inner envelope membranes from spinach chloroplasts were analyzed. Both envelope membranes contain prenylquinones, and in almost similar amounts (on a protein basis). However, the outer envelope membrane contains more -tocopherol than the inner one although this prenylquinone is the major one in both fractions. On the contrary, plastoquinone-9 is present in higher amounts in the inner envelope membrane than in the outer one. In addition, it has been demonstrated that all the enzymes involved in the last steps of -tocopherol and plastoquinone-9 biosynthesis i.e., homogentisate decarboxylase polyprenyltransferase, S-adenosyl-methionine: methyl-6-phytylquinol methyltransferase, S-adenosyl-methionine: -tocopherol methyltransferase, homogentisate decarboxylase solanesyltransferase, S-adenosyl-methionine:methyl-6-solanesylquinol methyltransferase, and possibly 2,3-dimethylphytylquinol cyclase, are localized on the inner envelope membrane. These results demonstrate that the inner membrane of the chloroplast envelope plays a key role in chloroplast biogenesis, and especially for the synthesis of the two major plastid prenylquinones