Vit E 6 pp - Vitamin E: History Vitamin E Evans & Bishop...

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Vitamin E Spring 2011 Vitamin E: History • Evans & Bishop discovered – wheat germ oil cured reproductive failure in rats fed rancid fat • Evans isolated vitamin E from wheat germ and named the factor “tocopherol” from Greek “tokos” meaning “offspring” and “pherein” meaning to “bear” Chemical Forms of Vitamin E • Vitamin E name includes 8 different forms • 4 tocophenols and 4 tocotrienols • tocotrienols differ from tocopherols –Unsaturated side chain Form that Meets Human Requirement • Food and Nutrition Board defined -tocopherol as only form that meets human vitamin E requirement –only -tocopherol shown to reverse deficiency symptoms Naturally-Occurring Stereoisomer in food is RRR - -tocopherol carbons at the 2, 4, 8 position in R position
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Synthetic Vitamin E • Chemically synthesized -tocopherol is not identical to naturally occurring form in food • Chemical synthesis produces 8 different stereoisomers – mixture of 8 stereoisomers referred to as mixture of 8 stereoisomers referred to as all-rac - -tocopherol – Only 4 of these are biologically active- stereoisomers- must be 2 R forms RR SR RS SS Biologically Active Forms Synthetic Vitamin E • Chemically synthesized -tocopherol Only half of the stereoisomers in al • Only half of the stereoisomers in all- rac- - tocopherol meet human requirement Blood tocopherol response to labeled (d3 and d6) dose of 150 mg each of d3 RRR - -andd6 all rac - -tocopherol Vitamin E: Food Sources •Ma jo r sou r ce s – Vegetable oils –Margarine – Mayonnaise –Wheat germ – Nuts, seeds
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Stability of Vitamin E • Oxidized easily –light, heat, or metals destruction • Esterification of synthetic form –prevents oxidation/extends shelf life Vitamin E Absorption • Vitamin E absorbed along with fats as component of micelles into intestinal cells – all chemical forms are incorporated into chylomicrons inside intestinal cells • Fat malabsorption can result in vit E deficiency – Cystic fibrosis (pancreatic lipase deficiency) – Cholestasis (decreased bile production) – Celiac disease Vitamin E Transport • Unlike other fat-soluble vitamins, vitamin E does not have a specific transport protein • Transported as a component of plasma lipoproteins • Chylomicron remnants transport to live • Chylomicron remnants transport to liver • Liver exports -tocopherol into plasma as component of VLDL – secretion of -tocopherol into plasma under control of -tocopherol transfer protein ( -TPP) • genetic defect in synthesis of -TPP leads to vitamin E deficiency -Tocopherol Transfer Protein -tocopherol transfer protein ( -TPP) involved in transfer of -tocopherol from liver to lipoproteins • Vitamin E forms are not interconvertible because their plasma concentrations are
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This note was uploaded on 12/09/2011 for the course HUN 4445 taught by Professor Sitren during the Spring '08 term at University of Florida.

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Vit E 6 pp - Vitamin E: History Vitamin E Evans & Bishop...

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