Vitamin E Flashcards
what is the active form
alpha tocopherol
2 types of vitamers and subcategories
tocoPHEROLS and tocoTRIENOLS
each as alpha, beta, gamma, delta
how is a-T transported
in plasma VLDL using specific a-T transfer protein (a-TTP), transported with LDL
notable feature of structures
OH end is polar and allows it to donate e- to free radical
Tocotrienols – tri because three double bonds
Tocotrienols are unsaturated fats, more mobile in a membrane
natural form (sterochemistry) of a-T
RRR
a-TTP and RRR a-T
binding affinity = 100% = very specific
how is natural E wrote on supplements? synthetic?
natural= RRR= d
synthetic= dl
biological active steriosomers
only carbon 2 R
RRR, RSR, RRS, RSS
biologically inactive stereoisomers
SSS, SSR, SRS, SRR
synthetic activity vs natural
synthetic (dl) has all 8 isomers, but only half are active
natural (d) has 4 active
2 functions of vitamin E
protect PUFAs (polyunsaturated fatty acids)
prevents LDL cholesterol oxidation
E mechanism of antioxidant
donate H+ in lipid bilayer (present as EH tocopherol, inserted between phospholipids using lipophilic tail)
effective against lipid peroxidases
EH + LOO (lipid peroxyl radical) -> LOOH (lipid hydroperoxide) + E radical
GSH needed to change LOOH to LOH (lipid alcohol)
Vit C regenerates E radical -> EH
food sources of E
wheat germ oil
sunflower oil
almosnds
hazlenuts
sunflower seeds
Vitamin E deficiency causes
- genetic defects in lipoprotein synthesis (impairs E transport)
- premature birth (may need supplements)
- Fat malabsorption syndrome
a. biliary cirrhosis
b. cystic fibrosis
c. short bowel syndrome
d. chronic pancreatitis
e. wt loss surgery
E is fat-soluble vitamin
Vitamin E deficiency symptoms humans
lose muscle = skeletal myopathy
blindness =retinopathy
reduced RBC half-life (cell membranes damaged)
immunological impairment
Vitamin E deficiency Symptoms in animals
reproductive failure, more muscle damage than humans
Vitamin E UL set from
animal data
how much would cause hemorrhage **bc E interferes with Vitamin K, no clotting
what is Vitamin E UL
1g d-aT natural or synthetic in supplements or fortified foods
**does not include natural Vitamin E in foods
RDA for Vitamin E
15mg d-aT
why are vitamin E radicals stable
delocalized e- is stable throughout ring structure
Lipid peroxidation initiation step
LH + OH radical = Lipid radical + H20
Lipid peroxidation propagation
Lipid radical + O2 = LOO radical
LOO radical + new LH = LOOH + new L radical
Lipid peroxidation termination
LOO radical + EH = LOOH + E radical
LOOH + 2 GSH = LOH + H2O + GSSG
lipid peroxidation regeneration
AH + E radical = A radical + EH
A radical + 2 GSH = AH + GSSG
GSSG + NADPH = 2 GSH + NADP+
Vitamin E EAR based on
= 12mg a-T
RBC hemolysis test, time for hemolysis if RBCs in dilute H2O2 is less if a person is deficient – membrane role
how to assess E status reasoning
E stored in adipose
travels with lipoproteins: chylomircons, VLDL, LDL, and HDL
PLASMA LEVELS of a-T = E transported with LDL
E functional test to assess
test RBC for hemolyze
add H2O2 to cells and count time for RBC to hemolysis
faster rate of hemolysis = low E bc cell membranes are weakened quickly and lack protection against oxidation
% of Vitamin E absorbed
50%
