Vitamin E and K - Vitamin E Function Antioxidant Protects...

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Vitamin E • Function – Antioxidant Protects cell membranes from free radicals From: Insel, Turner and Ross; Nutrition, 2nd Edition
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Vitamin E is a generic term used for a family of chemically- similar compounds sharing the tocopherol and tocotrienol structures. Vitamin E is a fat-soluble vitamin. Vitamin E ( α -tocopherol)
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α -tocopherol γ -tocopherol
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Type R1 R2 R3 α -Tocotrienol Me Me Me ß Tocotrienol Me H Me γ Tocotrienol Me Me H δ Tocotrienol Me H H Tocotrienol α -Tocopherol R1 R3 R2
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Tocopherols are able to interrupt free radical chain reactions by capturing the free radical; this imparts antioxidant properties. The hydroxyl group on the aromatic ring is responsible for the antioxidant properties. The hydrogen from this group is donated to the free radical, resulting in a relatively stable free radical form of the vitamin. Resonance stabilized radical
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The antioxidant network showing the interaction between vitamin E, vitamin C and thiol redox cycles, as well as their cellular localization. ROS and products of lipid peroxidation present in the cytosol or cell membrane may be detoxified by this system. ROO, peroxyl radical; RO, alkoxyl radical. FROM: Antioxidants and polyunsaturated fatty acids (2009) M E van Meeteren, C E Teunissen, C D Dijkstra and E A F van Tol. European Journal of Clinical Nutrition 59, 1347-1361.
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Vitamin E protects membrane lipids from oxidation Because of its lipophilic properties vitamin E is able to scavenge free radicals that are generated in membranes and lipoproteins. The high content of unsaturated fatty acids in membranes makes them good targets for free radical oxidation. Uncontrolled free radical oxidation of membrane lipids damages membrane integrity. Vitamin E prevents propagation of free radical reactions in membranes.
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Vitamin E absorption and transport Vitamin E is absorbed from the lumen of the small intestine into enterocytes by passive diffusion.
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