Vitamin E natural Vitamin E natural compoundscompounds

Alpha-Tocopherol a.k.a. Vitamin E

Vitamin E• Vitamin E is a famil of tocopherols and

corresponding tocotrienols izomers.• They are formed from chroman ring and hydrofobic

fytyl side chain. • The highest biological activity has -tokoferol.

Vitamin E as an antioxidant

O

R3

R2

HO

R1

Chromane Head

Phythyl Tail

R1 R2 R3 CH 3 CH 3 CH 3 CH 3 H CH 3 H CH 3 CH 3 H H CH 3

.

OCH3

CH3

CH3

O

CH3

(CH2)3CH(CH2)3CH(CH2)3CH(CH3)2

CH3 CH3

R + TOH RH + TO

Vitamin E as antioxidant• Stops free radical reactions (peroxyl radicals ROO , oxygen radicals

HO, lipoperoxid radicals LOO). Chroman ring with OH group → uptake radicals.

Oxidativedamage

Freeradicals Quenched

radical

Vitamin E FunctionVitamin E Function

Absorption and Transport

• Dependent on ability to absorb fat• Absorbed into lymphatic system• Component of chylomicrons• Alpha-tocopherol is major tocopherol in

plasma• Positive association between serum lipid and

tocopherol levels• Normal range is 0.5-1.6 mg/dl

E-Facts• Plays a role in immune function, DNA repair, other

metabolic processes, and in protecting other antioxidants

• U.S. RDA : 15 mg (22.5 IU) per day

• Typical Western diet provides 14 mg (21 IU) of Vit E

• Upper allowable intake (prior to Meta-Analysis): 1000mg (1500 IU)

2005 Annals of Int Med: “Meta-Analysis: High-Dosage Vitamin E Supplementation

May Increase All-Cause Mortality” • Three previous meta-analyses that did

not consider the dose-dependent effect of vitamin E concluded that vitamin E was neither beneficial nor harmful.

• New Conclusion based on 19 randomized controlled trials: High-dosage (>=400 IU/d) vitamin E supplements may increase all-cause mortality and should be avoided.

Health Hopes of Vitamin E

• Heart Disease: Mixed results

• Cancer: Promising but not conclusive– Breast cancer: two opposing studies– Colon and G.I. cancer: probably no benefit– Prostate and bladder cancer: possible benefit

• Alzheimer’s: theoretical but not well studied

Vitamin E & Cataracts• 1998: “Antioxidant vitamins and nuclear opacities:

the longitudinal study of cataract”– Cataract risk reduced by ½ in Vit E supplement users– 764 participant observational study (low significance)

However,

• 1997: “Long-term supplementation with alpha-tocopherol and beta-carotene and age-related cataract”– No benefit to Middle-aged male smokers taking vitamin

E supplements on the incidence of cataract formation