Antioxidant effects of α‐ and <sub>γ</sub>‐carboxyethyl‐6‐hydroxychromans

Yoshida, Yasuyuki; Niki, Etsuo

doi:10.1002/biof.5520160305

Cited by 20 publications

(13 citation statements)

References 32 publications

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“…Recently, CEHCs have been reported to have potential health benefits (22-25) as well as antioxidant functions (26,27). These latter functions are questionable because of the extremely low CEHC concentrations in human plasma (14,15,18,22).…”

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confidence: 99%

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Leonard

Gumpricht

Devereaux

et al. 2005

Journal of Lipid Research

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Vitamin E is a term encompassing a group of lipid-soluble, chain-breaking antioxidants that include ␣ -, ␤ -, ␥ -, and ␦ -tocopherol and the corresponding tocotrienols (1). Vitamin E differs from other fat-soluble vitamins in that it is not accumulated in the liver to toxic levels during times of excess intake (1). A high rate of vitamin E metabolism and/or excretion may be important in preventing adverse effects (2), but this hypothesis has not yet been tested. Tocopherols and tocotrienols are not only excreted directly but can be metabolized in the liver by hepatocytes (3-5); other tissues involved in vitamin E metabolism have not been specifically identified.␣ -and ␥ -tocopherols are converted to their respective carboxyethyl hydroxychroman (CEHC) derivatives, ␣ -CEHC [2,5,7,8-tetramethyl-2-(2 Ј -carboxyethyl)-6-hydroxychroman] and ␥ -CEHC [2,7,8-trimethyl-2-(2 Ј -carboxyethyl)-6-hydroxychroman] ( Fig. 1 ). The specific steps involved in vitamin E metabolism have been identified in vitro using HepG2 cells. These steps initially involve -oxidation by cytochrome P450 enzymes followed by ␤ -oxidative degradation (3, 4, 6).To evaluate in vivo metabolism of tocopherols, metabolite concentrations have been measured in human urine (5, 7-13), human plasma (5,(13)(14)(15)(16)(17)(18)(19), and rat bile (20,21). Recently, CEHCs have been reported to have potential health benefits (22-25) as well as antioxidant functions (26,27). These latter functions are questionable because of the extremely low CEHC concentrations in human plasma (14,15,18,22). There have also been discussions of the use of metabolite concentrations found in urine and plasma as indicators of vitamin E status (7,8,14,28,29), but, as this area is still fairly new and evolving, there is no clear evidence to support the use of metabolites as vitamin E status indicators.To our knowledge, there are no reports on tissue metabolite concentrations. Based on tissue culture studies of metabolite formation by hepatocytes (3-5), it is likely that CEHCs are produced in the liver. Therefore, we have deAbbreviations: CEHC, carboxyethyl hydroxychroman; LC-MS, liquid chromatography-mass spectrometry; MDR1, multidrug resistance protein-1; m/z , mass-to-charge ratio; SXR, steroid and xenobiotic receptor; UGT1A1, UDP-glucuronosyltransferase-1A1.

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confidence: 99%

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Leonard

Gumpricht

Devereaux

et al. 2005

Journal of Lipid Research

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“…Although this example illustrates the difference between apparent and membrane concentrations of TQ and Toc, the value of this formula is limited since the lipid volume and the partition coefficients are very rough approximations. For example, Yoshida and Niki reported a log P OW values for a-Toc of 3.36 [84], whereas all theoretical calculations predict values of 9 and above [85,86].…”

Section: Tq and Toc As Modulators Of Mitochondrial Electron Transfermentioning

confidence: 88%

Tocopheryl quinones and mitochondria

Gille

Staniek

Rosenau

et al. 2010

Molecular Nutrition Food Res

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In the past, the role of tocopherols and tocopheryl hydroquinones as antioxidants in mitochondria has been examined. However, structural properties of tocopherols and tocopheryl quinones (arrangement of polar/apolar moieties) have also been recognized as being crucial for the selective transport of RRR-alpha-congeners compared with other tocopherols in the cell, suggesting that these properties might be generally important for the binding of vitamin E-related compounds to proteins and enzymes in mitochondria. Therefore, direct modulation of mitochondrial activities, such as bioenergetics, production of reactive oxygen species and apoptosis, not exclusively related to the redox activity of these compounds is increasingly studied. This overview focuses on the influence of alpha-/gamma-tocopheryl quinones and their parent alpha-/gamma-tocopherols on mitochondrial functions, including formation of tocopheryl quinones, their analytical aspects, their potential as alternative substrates and their inhibitory activity for some mitochondrial functions. It is shown that the understanding of how tocopheryl quinones and tocopherols interfere with mitochondrial functions on the molecular level is still incomplete and that a better comprehension requires further research activities.

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“…Yoshida and Niki (13) indicated that CEHC scavenged aqueous radicals but inhibited lipid peroxidation within membranes less efficiently than the corresponding ␣-Toc and ␥-Toc. Furthermore, the present study showed that ␣-Toc and CEHC might act as coantioxidants with the oxidation of LDL.…”

Section: Discussionmentioning

confidence: 99%

“…Vitamin C can also prevent the pro-oxidative activity of ␣-Toc by reducing the ␣-tocopheroxyl radical to ␣-Toc, thereby acting as a coantioxidant and regenerate ␣-Toc (7). Yoshida and Niki (13) indicated that CEHC inhibited lipid peroxidation within the membranes less efficiently than the corresponding ␣-Toc and ␥-Toc. However, the present study showed that CEHC might have the potential to delay the oxidation of LDL as a water soluble antioxidant (such as vitamin C, uric acid, sesame lignans, or tea catechin).…”

Section: Discussionmentioning

confidence: 99%

The Coantioxidative Effects of Carboxyethyl-6-Hydroxychromans and .ALPHA.-Tocopherol

Uto‐Kondo

Kiyose

Ohmori

et al. 2007

J Nutr Sci Vitaminol

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Summary ␣ -Tocopherol ( ␣ -Toc) is abundant in LDL and thought to prevent the oxidation of LDL together with various water-soluble antioxidants. Recently, it was reported that ␣ -Toc and ␥ -Toc metabolites, ␣ -carboxyethyl-6-hydroxychromans (CEHC) and ␥ -CEHC, are watersoluble antioxidants. In this study, we investigated the interaction between ␣ -Toc and CEHC against 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals and LDL oxidation. We administered 600 mg of ␣ -Toc to healthy male volunteers to obtain LDL including high levels of ␣ -Toc before antioxidant administration. The ␣ -Toc content of their LDL was increased after consumption at 24 h (18.3 g/mL) above the level before consumption (6.6 g/mL). The lag time of LDL at 24 h after ␣ -Toc consumption ( ␣ -Toc rich LDL) with ␣ -CEHC (98.5 Ϯ 8.2 min) or ␥ -CEHC (101.3 Ϯ 9.0 min) was longer than that of only ␣ -Toc-rich LDL (78.1 Ϯ 9.0 min). Furthermore, we examined the interaction of LDL with CEHC and ␣ -Toc in vitro (5-20 g/mL). The lag times of 5 and 10 g/mL ␣ -Toc were 65.5 Ϯ 18.9 min and 69.5 Ϯ 15.5 min, and that of 20 g/mL ␣ -Toc (83.5 Ϯ 20.2 min) was longer than the control value (55.7 Ϯ 14.1 min). The lag time of 20 g/mL ␣ -Toc with ␣ -CEHC (98.7 Ϯ 25.7 min) or ␥ -CEHC (100.6 Ϯ 25.3 min) was longer than that of only ␣ -Toc (83.5 Ϯ 20.2 min). These results suggest that CEHC has the potential to delay the oxidation of LDL, while enhancing the antioxidative activity of ␣ -Toc both in vitro and ex vivo.

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Antioxidant effects of α‐ and _γ‐carboxyethyl‐6‐hydroxychromans

Cited by 20 publications

References 32 publications

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Tocopheryl quinones and mitochondria

The Coantioxidative Effects of Carboxyethyl-6-Hydroxychromans and .ALPHA.-Tocopherol

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Antioxidant effects of α‐ and γ‐carboxyethyl‐6‐hydroxychromans

Cited by 20 publications

References 32 publications

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Quantitation of rat liver vitamin E metabolites by LC-MS during high-dose vitamin E administration

Tocopheryl quinones and mitochondria

The Coantioxidative Effects of Carboxyethyl-6-Hydroxychromans and .ALPHA.-Tocopherol

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Antioxidant effects of α‐ and _γ‐carboxyethyl‐6‐hydroxychromans