Lec 10: Vitamin E

Vitamin

organic micronutrient needed for cell function and metabolism, 13 essential vitamins

Fat-soluble vitamins

A, D, E, K

Water-soluble vitamins

folate, thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, vitamin B12, and vitamin C

Vitamin E discovery

1992, necessary for reproductive ability in rodents

Vitamin E activity and sources

antioxidant, nuts, seeds, green leaf vegetables

Vitamin E structure

Compounds made up of eight fat-soluble compounds, four tocopherols and four tocotrienols, chromane (head, benzene: pyran, furan)and phytyl tail (fatty tail) are key structural components

Tocopherol vs tocotrienol structure

tocopherol: saturated phytyl tail (NO DOUBLE BONDS) and tocotrienol has an unsaturated tail (CONTAINS DOUBLE BONDS).

Tocopherol is less flexible

Tocopherol exists in ... forms

four, alpha, beta, gamma, and delta

Tocopherol forms differ based on

the number and position of the methyl groups on the chromanol head (the heterocyclic compound that acts as the parent nucleus of the tocopherols)

alpha-tocopherol structure

chromanol head is fully methylated and the phytyl tail is saturated

Physiochemical properties of vitamin E

1. tocopherols are viscous oils at room temp

2. Insoluble in water but soluble in ethanol and aprotic solvents (DMF, DMSO, acetone, don't give hydrogens)

3. slightly yellow/amber, odorless, clear, viscous oil

4. Exist as a powder in encapsulated form

partition coefficient

Lipid solubility measure, disbursement in oil/water aka concentration in organic phase/ concentration in aqueous phase, serves as a measure of how compounds partition between oil/water. HIGH PC=LIPID SOLUBLE, LOW PC= WATER SOLUBLE

Sources of vitamin E

seeds, fruits, green leafy vegetables

alpha-tocopherol can be extracted from and is only synthesized in

purified or concentrated vegetables and pant extracts, only synthesized in plants and photosynthetic organisms

Vitamin E extraction pathway

1. Oil extraction: seeds are pressed or solvent extracted

2. Degumming: removes phospholipids and free fatty acids

3. Deodorization: produces deodorizer distillate

4. Saponification: removes fatty acids using alkali

Vitamin E solvent extraction

tocopherols are separated using organic solvents, distillation and chromatographic separation are HIGHER-PURITY methods

Lipid digestion: goal of fat digestion

dismantle triglycerides (monoglycerides, fatty acids, and glycerol), but fats are hydrophobic and digestive enzymes are hydrophilic

Phases of lipid digestion

1. Lingual lipase

2. Gastric lipase

3. Bile

4. Pancreatic lipase

5. Phospholipase A2

6. Hepatic lipase

7. Endothelial lipase

8. Lipoprotein lipase

Lipid digestion in the mouth/stomach

Mouth: lingual lipase

Stomach: muscle contractions and gastric lipase

Lipid digestion in the small intestine

Cholecystokinin (CCK): gallbladder releases bile, bile acts as emulsifier

Pancreatic lipase, hydrolysis: triglycerides and phospholipids, bile routes

Impacts blood cholesterol levels

Emulsification of Fat by Bile

1. Fat and watery GI juice do not mix

2. Gallbladder secrets bile when the fat enters the small intestine

3. Bile breaks down large fat molecules into small droplets that are hydrophilic

4. After bile emulsification, the hydrophilic droplets are digested by hydrophilic lipase

Hydrolysis of a Triglyceride

Triglyceride ---> monoglyceride + two fatty acids

Enterohepatic Circulation of Bile

1. Liver makes bile from cholesterol

2. Gallbladder stores bile

3. In the small intestine bule emulsifies fats

4. Bile is then reabsorbed into the blood and the process starts again OR in the colon, the bile trapped by soluble fibers is excreted

Micelle formation

formed in the lumen of the small intestine, complex of lipid materials (but soluble in water), contains bile salts, phospholipids, and cholesterol. Combines with 2-monoglycerides, free fatty acids, and fat-soluble vitamins to form mixed micelles

Lipid Absorption

1. Directly into the bloodstream (glycerol and short/medium chain fatty acids)

2. Lymphatic system (micelles diffuse into intestinal cells, reassembly of triglycerides, packed with proteins-chylomicrons, bypass liver at first)