07-VITAMINS 2 Water Soluble AmiJS

8/9/2019 07-VITAMINS 2 Water Soluble AmiJS

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The Water-Soluble Vitamins


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Vitamins are precursors of cofactors


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The B vitamins are: Vitamin B-1 ( Thiamine )

Vitamin B-2, also Vitamin G (Riboflavin )Vitamin B-3, also Vitamin P or Vitamin PP ( Niacin )

Vitamin B-5 ( Pantothenic acid )Vitamin B-6 ( Pyridoxine and Pyridoxamine )Vitamin B-7, also Vitamin H ( Biotin )

Vitamin B-9, also Vitamin M ( Folic acid ) - important for pregnanciesVitamin B-12 ( Cyanocobalamin )

Several other substances which are not human vitamins have been referred to as B vitamins.

These include: Vitamin B-4 ( Adenine )

Vitamin B-7* — more commonly called Vitamin IVitamin B-8 ( Ergadenylic acid )

Vitamin B-10, also Vitamin R ( Pteroylmonoglutamic acid mixed with other B vitamins )Vitamin B-11, also Vitamin S

Vitamin B-13 (Pyrimidinecarboxylic acid or orotic acid, often misspelled erotic acid)Vitamin B-14 — a mixture of B-10 and B-11

Vitamin B-15 ( Pangamic acid )Vitamin B-16

Vitamin B-17 ( Amygdalin )Vitamin B-22, often claimed as an ingredient of Aloe vera extracts

Vitamin B-c, another name for Vitamin B-9 ( Folic acid )


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Overview of Water-Soluble

Vitamins• Dissolve in water• Generally readily excreted• Subject to cooking losses• Function as a coenzyme

• Participate in energy metabolism• 50-90% of B vitamins are absorbed• Marginal deficiency more common


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Enrichment Act of 1941 and 1998

• Many nutrients lost through milling processof grains

• Grain/cereal products are enriched• Thiamin, riboflavin, niacin, folate, iron• Whole grains contain original nutrients• Enriched grains still deficient in B-6,

magnesium and zinc


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Thiamin = Vitamin B1

• Contains sulfur and nitrogen group• Destroyed by alkaline and heat• Coenzyme: Thiamin pyrophosphate (TPP)

C

N

CH

C

CN

HC

NCH

CH

S

H 3 C

CH 2

NH 3

Cl-

+


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Food Sources of Thiamin

• Wide variety of food• White bread, pork, hot dogs, luncheon meat,

cold cereal• Enriched grains/ whole grains• Thiaminase found in raw fish


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Absorption, Transport,

Metabolism of Thiamin• Absorbed in the jejunum by a carrier-

mediated system• Transported by RBC in the blood• Excess quickly excreted in the urine


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Function of Thiamin


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Coenzyme: Thiamin

Pyrophosphate (TPP)

• Synthesis of neurotransmitter• Convert pyruvate to acetyl-CoA

CoA NAD + NADH + H +

Glucose Pyruvate Acetyl-CoA CitricCO 2 Acid Cycle


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RDA(Recommended Dietary

Allowance) For Thiamin• 1.1 mg/day for women• 1.2 mg/day for men• Most exceed RDA in diet• Surplus is rapidly lost in urine; non toxic


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Who is at Risk For Deficiency?

• Poor• Alcoholics• Elderly• Diet consisting of highly processed foods


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Deficiency of Thiamin

• Occurs where rice is the only staple• Dry beriberi

– Weakness, nerve degeneration, irritability, poorarm/leg coordination, loss of nervetransmission

• Wet beriberi – Edema, enlarge heart, heart failure


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Riboflavin = Vitamin B2

• Coenzymes: – Flavin mononucleotide ( FMN )

– Flavin adenine dinucleotide ( FAD )

• Oxidation-reduction reactions• Electron transport chain• Citric Acid Cycle• Catabolism of fatty acids

N

N

NH

NH 3 C

H 3 C

O

O

CH

CH

CH

CH

CH 2 OH

HO

HO

HO

H


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Food Sources of Riboflavin

• Milk/products• Enriched grains• Liver• Oyster

• Brewer’s yeast • Sensitive to uv radiation (sunlight)• Stored in paper, opaque plastic containers


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Absorption, Transport, &

Metabolism of Riboflavin• HCl in the stomach release riboflavin from

its bound forms

• Absorption – Active or facilitated transport during low to

moderate intake – Passive absorption during high intake – Increase with intake

• Transported by a protein carrier in the blood


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Functions of Riboflavin

• Accepts electronsElectron Transport Chain

FAD FADH 2

Succinate FumarateCitric Acid Cycle

• Participates in beta oxidation• FMN shuttles hydrogen ions and electrons to into

the electron transport chain


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RDA for Riboflavin

• 1.1 mg/day for women• 1.3 mg/day for men• Average intake is above RDA• Toxicity not documented


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– Rare – Low milk/dairy intake

– Alcoholics – Long term phenobarbital use


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Deficiency of Riboflavin

• Ariboflavinosis – Glossitis, cheilosis, seborrheic dermatitis,

stomatitis, eye disorder, throat disorder,nervous system disorder

• Occurs within 2 months

• Usually in combination with otherdeficiencies


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Glossitis (Fig. 10-4)


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Niacin

• Nicotinic acid (niacin) & nicotinamide(niacinamide)

• Coenzyme – Nicotinamide adenine dinucleotide ( NAD ) – Nicotinamide adenine dinucleotide phosphate

(NADP )• Oxidation-reduction reaction• Metabolic reactions


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Food Sources of Niacin

• Mushrooms• Enriched grains• Beef, chicken, turkey, fish• Heat stable; little cooking loss


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Absorption, Transport and

Storage of Niacin• Readily absorbed from the stomach and

small intestine• Absorption: active transport and passive

diffusion

• Transported from the liver to all of thetissues where it is converted to thecoenzymes


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Functions of Niacin• NAD and NADP participates in 200+ reactions in the body

2 NAD + 2NADH + H +

Glucose Pyruvate

NAD + NADH + H + Pyruvate Lactate

NAD + NADH + H + Isocitrate Alpha-ketogluterate

NAD+

NADH + H+

Alpha-ketogluterate Succinyl CoA

NAD + NADH + H + Malate Oxaloacetate

• Electron transport chain

Citric AcidCycle


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RDA for Niacin

• 14 mg/day for women• 16 mg/day for men• 18 mg/day pregnant/ breast feeding women


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Deficiency of Niacin• Pellagra

– Occurs in 50-60 days – Decrease appetite & weight

• Prevented with an adequate protein diet• Enrichment Act of 1941• Only dietary deficiency disease to reach epidemic

proportions in the U.S.• Who is at risk?

– (Untreated) corn as main staple, poor diet,Hartnup disease (semacam pellagra), alcoholics


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Dermatitis of Pellegra (Fig. 10-5)


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Niacin as a Medicine

• 75-100 x RDA can lower LDL and TG andincrease HDL

• Slow/ reverse progression ofatheroscelerosis with diet and exercise

• Toxicity effects – Flushing of skin, itching, nausea, liver damage


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Pantothenic Acid

• Part of Coenzyme-A• Essential for metabolism of CHO, fat,

protein

Glucose

Fatty acids Acetyl-CoA Amino Acids

Alcohol

H 3 C CHC C

HN

H 2C

H 2C C

O

OH

CH 3

CH 2 OH

HO

O


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Food Sources of Pantothenic acid

• Meat, milk• Mushroom

• Liver• Peanut• Adequate Intake = 5 mg/day

Adenosin 2’,3’ -fosfat – Pyrofosfat – Panthothenat – Beta-merkapto etil amina

(= Coenzim A )


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Deficiency of Pantothenic

Acid• Rare• Burning foot syndrome, listlessness,

fatigue, headache, sleep disturbance,nausea, abdominal distress

• Alcoholics at risk• Usually in combination with other

deficiencies


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Biotin = Vitamin B7 = Vitamin H• Free and bound form• Biocytin (protein bound form)

• Biotinidase in small intestine• Metabolism of CHO, fat, protein (C

skeleton)

• DNA synthesis• Co- enzyme R

HN NH

CHH 2 C

S

O

CH 2

H 2C

CH 2

H 2C

C

OH

O


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Food Sources of Biotin

• Cauliflower, yolk, liver, peanuts, cheese• Intestinal synthesis of biotin• Biotin content only available for a small number

of foods• Unsure as to bioavailablity of synthesized biotin• We excrete more than we consume

• Avidin inhibits absorption – > a dozen of raw eggs a day to cause this effect


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Functions of Biotin• Assists in the addition of CO 2 to substances• Carboxylation of acetyl-CoA to form

malonyl-CoA for the elongation of a fattyacid chain

• Addition of CO 2 to pyruvate to yieldoxaloacetate

• Breaks down leucine• Allows 3 essential amino acids to be

oxidized for energy


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Biotin Needs

• Adequate Intake is 30 ug/day for adults• This may overestimate the amount needed for

adults• No Upper Limit for biotin

• Biotin-enzim + HCO 3 - +ATP CO 2-Biotin-enzim + ADP + Pi


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• Rare• High intake of raw egg white diet (avidin-

biotin)• Alcoholics• Biotinidase deficiency

• Anticonvulsant drug use• Signs & symptoms: skin rash, hair loss,convulsion, neurological disorders,impaired growth in children


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Vitamin B-6: Pyridoxal,

Pyridoxine, Pyridoxamine• Main coenzyme form: pyridoxal phosphate

(PLP )

• Activate enzymes needed for metabolism ofCHO, fat , protein

• Transamination

• Synthesis of hemoglobin and oxygen binding and white blood cells

• Synthesis of neurotransmitters


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Food Sources of Vitamin B-6

• Meat, fish, poultry• Whole grains (not enriched back)

• Banana, Spinach, Avocado, potato• Heat and alkaline sensitive

N

CH 2 OH

CH 2 OH

HO

H 3 C

Piridoksin

N

CH 2 OH

C

HO

H 3 C

OH

Piridoksal

Oksidasi


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Absorption and Metabolism of

Vitamin B-6• Absorbed passively• All three forms of B-6 are phosphorylated

in the liver• Binds to albumin for transport in the blood• B-6 is stored in the liver and muscle tissue• Excess is excreted in urine


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Functions of Vitamin B-6• Participates in 100+ enzymatic reactions• Decarboxylation of amino acid (decarboxylase)• Transamination reaction (transaminase)

• Structural rearrangement of amino acids(racemase)

• RBC synthesis• CHO metabolism• Lipid metabolism• Neurotransmitter Synthesis• Conversion of tryptophan to niacin


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RDA for Vitamin B-6

• 1.3 mg/day for adults• 1.7 mg/day for men over 50• 1.5 mg/day for women over 50• Daily Value set at 2 mg• Average intake is more than the RDA


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Deficiency of Vitamin B-6

• Microcytic hypochromic anemia• Seborrheic dermatitis• Convulsion, depression, confusion

• Reduce immune response• Peripheral nerve damage• Who is at r i sk?

– Elderly – Alcoholics

• Alcohol decreases absorption• Destroy the coenzyme form


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B-6 As A Medicine?

• PMS (Premenstrual Syndrome) – B-6 to increase the level of serotonin

– Improve depression – Not a reliable treatment

• Carpal tunnel syndrome

• Toxicity potential• Can lead to irreversible nerve damage with

> 200 mg/day


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Folate (Folic acid, Folacin)

• Consists of pteridine group, para-aminobenzoic acid (PABA), and glutamicacid

• Coenzyme form: tetrahydorfolic acid(THFA )


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Food Sources of Folate

• Liver• Fortified breakfast cereals• Grains, legumes• Foliage vegetables• Susceptible to heat, oxidation, ultraviolet

light


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Absorption, Metabolism of Folate

• Absorbed in the monoglutamate form with helpof folate conjugase• Actively absorbed during low to moderate

intake• Passively absorbed during high intake• Delivered to the liver where it is changed back

to the polyglutamate form• Mostly stored in the liver• Excreted in the urine and bile (enterohepatic

circulation)


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Functions of Folate

• DNA synthesis – Transfer of single carbon units

– Synthesis of adenine and guanine – Anticancer drug methotrexate

• Homocysteine metabolism

• Neurotransmitter formation


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RDA for Folate

• 400 ug/day for adults• Daily Value is set at 400 ug


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Deficiency of Folate

• Similar signs and symptoms of vitamin B-12 deficiency

• Pregnant women• Alcoholics

– Interferes with the enterohepatic circulation of

bile/folate

M l bl i A i


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Megaloblastic Anemia (Fig. 10-7)


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Neural Tube Defects

• Spina bifida• Anencephaly

• Importance of folate before and during pregnancy


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Toxicity of Folate

• Epilepsy• Skin, respiratory disorder• FDA limits nonprescription supplements to

400 ug per tablet for non-pregnant adults• OTC Prenatal supplement contains 800 ug• Excess can mask vitamin B-12 deficiency


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Vitamin B-12

• Cyanocobalamin. methlcobalamin,5-deoxyadenosylcobalamin• Contains cobalt• Folate metabolism• Maintenance of the myelin sheaths• Rearrange 3-carbon chain fatty acids so can

enter the Citric Acid Cycle


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Vitamin B12 =Cyanocobalamine


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Food Sources of Vitamin B-12

• Synthesized by bacteria, fungi and algae • (Stored primarily in the liver)

• Animal products• Organ meat• Seafood

• Eggs• Hot dogs• Milk

Absorption of Vitamin B 12 (Fi 10 10)


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Absorption of Vitamin B-12 (Fig. 10-10)


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Therapy for Ineffective

Absorption

• Many factors can disrupt this process

• Monthly injections of vitamin B-12• Vitamin B-12 nasal gel• Megadoses of vitamin B-12 to allow for

passive diffusion


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Functions of Vitamin B-12

• Helps convert methylmalonyl CoA tosuccinyl CoA (citric acid cycle)

• RBC formation• Nerve functions

– Maintains myelin sheath

• Megalobalstic anemia

Vitamin B 12 and Homocysteine


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Vitamin B-12 and Homocysteine(Fig. 10-11)


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RDA for Vitamin B-12

• 2.4 ug/ day for adults and elderlyadults

• Average intake exceeds RDA

• B-12 stored in the liver• Non-toxic


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• Vegans• Breastfed infants of vegan moms

• Elderly• Individuals with AIDS or HIV


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Deficiency of Vitamin B-12• Pernicious anemia

– Never degeneration, weakness – Tingling/numbness in the extremities (parasthesia)

– Paralysis and death – Looks like folate deficiency

• Usually due to decreased absorption ability• Achlorhydria especially in elderly• Injection of B-12 needed• Takes ~20 years on a deficient diet to see

nerve destruction


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Non-B Vitamin

• Controversial other dietary compounds• Still under scientific investigation

• May be “conditionally” essential • Supplements NOT necessary• Widespread in foods


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Non-B Vitamin

• Choline – Contains N 2; made from methionine – Used to make lecithin & acetylcholine

– Adequate Intake (AI) established 1998• Men=550 mg/day; Women=425 mg/day

• Inositol – Part of cell membrane structure

• Carnitine

– Transports long-chain fatty acids

Vi i I


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Vitamin Imposters

• Not essential for humans; essential onlyfor bacteria or other forms of life• PABA (para-aminobenzoic acid) • Vitamin P (hesperidin)-a bioflavonoid• Ubiquinone (Coenzyme Q 10 )

• Pyrroloquinoline quinone (methoxatin)• Orotic acid• Lipoic acid

Vi i I


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Vitamin Imposters

• Vitamin O (oxygenated salt water)• Vitamin B 15 (Pangamic acid)

• Vitamin B 17 (Laetrile) – Alleged “cancer cure” – Potentially dangerous

• Vitamin B 5 – Simply another name for Pantothenic Acid


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Vitamin C

• Ascorbic acid (reduced form),dehydroascorbic acid (oxidized form)• Synthesized by most animals (not by

human)

• Absorbed by a specific energy dependanttransport system

• Passive transport if intake is high• Decrease absorption with high intakes• Excess excreted

CHOH

H

O

CH 2 OH

HOOH

Ascorbic Acid= Vitamin C


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Food Sources of Vitamin C

• Citrus fruits• Potatoes

• Green peppers• Cauliflower• Broccoli

• Strawberries• Romaine lettuce• Spinach

• Easily lost throughcooking

• Sensitive to heat• Sensitive to iron,

copper, oxygen


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Functions of Vitamin C

• Reducing agent (antioxidant)• Iron absorption

• Synthesis of carnitine, tryptophan toserotonin, thyroxine, cortiscosteroids,aldosterone, cholesterol to bile acids

• Immune functions• Cancer prevention?• Collagen synthesis


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N

N

CH 3

N

OH

C

O

HNO 3

Nicotine Nicotinic acid

N

C

O

Nicotinamide

HN 2

Collagen Synthesis (Fig 10-12)


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Collagen Synthesis (Fig. 10-12)


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Antioxidant

• Can donate and accept hydrogen atomsreadily

• Water-soluble intracellular andextracellular antioxidant

• Must be constantly enzymatically

regenerated• Needs are higher for smokers


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RDA for Vitamin C

• 90 mg/day for male adults• 75 mg/day for female adults

• +35 mg/day for smokers• Average intake ~72 mg/day• Fairly nontoxic (at


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Deficiency of Vitamin C• Scurvy

– Deficient for 20-40 days – Fatigue, pinpoint hemorrhages – Bleeding gums and joints. Hemorrhages – Associated with poverty

• Rebound scurvy – immediate halt to excess vitamin C

supplements• Who is at risk?

– Infants, elderly men

Documents

07-VITAMINS 2 Water Soluble AmiJS