vitamins 2553 chatchawin

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Vitamins

Vitamins

Medical Biochemistry Approach

Lecturer:

Chatchawin PETCHLERT, Ph.D.

Head, Department of Biochemistry

Deputy Head, Department of Biotechnology

Department of Biochemistry

Faculty of Science, Burapha University



VitaminsDepartment of Biochemistry


o Chemical structure

o Classification: Fat-soluble & water-soluble vitamins

o General functions

o Synthesis vitamin A, D, E & K

o Specific functions

o A, D, E & K

o B-group & C

o Anti-oxidative action: -carotene, vitamin E, C

o Requirements

o Cow¶s milk & vitamins

o Check your knowledge





VitaminsVitamins : organic, essential nutrients required in

small amounts to perform specific functions that

promote growth, reproduction, or the maintenance of

health and life.

VITAMINVITAMIN

VITAVITA(life)(life)

AMINEAMINE(containing nitrogen)(containing nitrogen)





A retinol phototransduction

D cholecalciferol bone remodeling

E E-tocopherol antioxidant

K phytylmenaquinone

multiprenylmenaquinonecoagulation

bone remodeling

B1 thiamin carbohydrate metabolism

B2 riboflavin redox, respiration

B3niacin redox

B6 pyridoxine pyridoxamine

pyridoxal

AA metabolismglycogenolysis

B5 pantothenic acid TCA, FA and cholesterol

B7 biotin gluconeogenesis, TCA, FA, AA

B12 cobalamin 1C&H metabolism

B9 folic acid 1C metabolism

C ascorbic acid hydroxylation



Vitamin-Like Substances

Choline Acetyl choline, Phospholipids

Carnitine Fatty acyl group transfer

Bioflavonoids Antioxidants

Lipoic acid TCA acyl group transfer

Coenzyme Q Electron transport

Inositol Phospholipids

p-Aminobenzoic acid Folate component







Vitamins : Overview First recognized that there were substances in foods that were

³vital to life´ in the early 1900s.

Vit. A deficiency can cause blindness; a lack of the B vitamin ±

niacin can cause dementia; and a lack of vit. D can retard bone

growth.

Vit. C not only prevents the deficiency disease scurvy, but also

seems to protect against certain types of cancer. Vit. E seems to help protect against some facets of CVD.

Vit. B folate helps to prevent birth defects.





Vitamins : OverviewVitamins differ from CHOs, fats, and proteins in the following

ways:

Structure. Vitamins are individual units; they are not linked together

(as are molecules of glucose or amino acids).

F unction. Vitamins do not yield usable energy when broken down;

they assist the enzymes that release energy from CHOs, fats, and

proteins. F ood contents. The amounts of vitamins people ingest daily from

foods and the amounts they require are measured in Qg or mg, rather

than g.





Vitamins : Functions Essential for many processes in the body

Vitamins play a role in digestion & utilization of

² Protein

² Fat

² Carbohydrates

Vitamins are components of enzymes (coenzyme particularly water-

soluble vitamins)





Vitamins : BioavailabilityBioavailability: the rate at and the extent to which a nutrient is absorbed and

used.

Precursors: substances that precede others; with regard to vitamins, compounds

that can be converted into active vitamins; also known as provitamins.provitamins.

Determining the bioavailability of a vitamin is a more complex task

because it depends on many factors, including:

efficiency of digestion and transit time through the GI tract.

previous nutrient intake and nutrition status.

other foods consumed at the same time that may inhibit or enhance the

absorption of individual vitamins and minerals.

method of food preparation (raw, cooked, or , processed).

source of the nutrient (synthetic, fortified, or naturally occurring).





Minimizing vitamin losses To slow the degradation of vitamins, refrigerate (most) fruits and vegetables.

To minimize the oxidation of vitamins, store fruits and vegetables that have been cut

in airtight wrappers and juices that have been opened in closed containers (and

refrigerated them).

To prevent losses during washing, rinse fruits and vegetables before cutting.

To minimize losses during cooking, use a microwave oven or steam vegetables in a

small amount of water. Add vegetables after water has come to a boil. Use the cooking

water in mixed dishes such as casseroles and soups. Avoid high temperatures and

long cooking times.





WaterWater--Soluble Vitamins:Soluble Vitamins:B Vitamins and Vitamin CB Vitamins and Vitamin C

FatFat--Soluble Vitamins:Soluble Vitamins:Vitamins A, D, E, and KVitamins A, D, E, and K

Absorption Directly into the blood First into the lymph, then the

blood

Transport Travel freely Many require protein carriers

Storage Circulate freely in water-filled

parts of the body

Stored in the cells associated

with fat

Excretion Kidneys detect and remove

excess in urine

Less readily excreted; tend to

remain in fat-storage sites

Toxicity Possible to reach toxic levels

when consumed from

supplements

Likely to reach toxic levels when

consumed from supplements

Requirements Needed in frequent doses

(perhaps 1 - 3 days)

Needed in periodic doses

(perhaps weeks or even months)





FatFat--SolubleSoluble

VitaminsVitamins





Vitamin A Vit. A was the first fat-soluble vitamin

to be recognized.

Precursors are carotenoids such as

F-carotene.

Different forms of vit. A are active in

the body: retinol, retinal, and retinoic

acid.

A special transport protein, retinol-

binding protein (RBP), picks up vit. A

from the liver, where it is stored, and

carries it in the blood.





Worldwide data of VAD in 2008





Forms of Vitamin A





Roles of Vitamins A Promoting vision

Participating in protein synthesis and cell

differentiation (and thereby maintaining the

health of epithelial tissues and skin)

Supporting reproduction and growth





Recommendation RD A : 900 Qg RAE/day (male)

700 Qg RAE/day (female)

1 Qg RAE = 1 Qg retinol= 2 Qg F-carotene (supplement)

= 12 Qg F-carotene (diet)

= 24 Qg of other vit. A precursor carotenoids

1 IU retinol = 0.3 Qg retinol or 0.3 Qg RAE

1 IU F-carotene (suppl.) = 0.5 IU retinol or 0.15 Qg RAE1 IU F-carotene (diet) = 0.165 IU retinol or 0.05 Qg RAE

1 IU other vit. A precursor carotenoids = 0.025 Qg RAE

Retinol activity equivalents (RAE): a measure of vit. A activity; the amount

of retinol that the body will derive from a food containing preformed retinol or

its precursor F-carotene.





Deficiency Disease and SymptomsHypovitaminosis A

Night blindness, corneal drying (xerosis), triangular gray spots on

eye (Bitot¶s spot), softening of the cornea (keratomalacia), and

corneal degeneration and blindness (xerophthalmia)

Impaired immunity (infectious diseases)

plugging of hair follicles with keratin, forming white lumps

(hyperkeratosis)





Conjunctival xerosis

Bitot¶s spot

Keratomalacia Corneal xerosis

Corneal scar





Toxicity = Hypervitaminosis A Bone defects osteoporosis (consuming

large amounts), increased activity of osteoclast

Birth defects teratogenesis risk (excess vit.

A before the 7th week of pregnancy appear to be

the most damaging)

Yellow skin but not harmful

Acne AccutaneAccutane is made from vit. A but is

chemically different. It is effective against the deep lesion of

cystic acne. It is highly toxic, however, especially during

growth, and has caused birth defects in infants when women

have taken it during their pregnancies.





Vitamins D (calciferol)

The body can synthesize vit. D by

sunlight exposure.

Vit. D comes in many forms, the 2

most important being a plant version

called vit. Dvit. D22 or ergocalciferolergocalciferol and an

animal version called vit. Dvit. D33 or

cholecalciferolcholecalciferol.

Active form is 1,25-dihydroxy

cholecalciferol (vit. D3).





Roles of Vitamin D

Mineralization of bones (raises blood Ca2+ and

P by increasing absorption from digestive tract,

withdrawing Ca2+ from bones

Stimulating retention by kidney

Vit. D may protect against multiple sclerosis





Recommendation Adequate Intake (AI) :

Adults: 5 Qg/day (19-50 y)

10 Qg/day (51-70 y)

15 Qg/day ("70 y)

1 IU = 0.025 Qg cholecalciferol (or vit. D3)





Deficiency Disease and Symptoms Rickets

Osteomalacia

Osteoporosis





Toxicity = Hypervitaminosis D Elevated blood Ca2+

Calcification of soft tissues (blood vessels, kidney, heart, lung,

tissues around joints)

frequent urination

Precaution

prolong exposure to sunlight degrades vit. D precursor in the skin.

prolong exposure to sunlight increase the risk of skin cancer.

sunscreens with sun protection factors (SPF) of 8 and higher also

prevent vit. D synthesis.





Vitamin E (Tocopherol) Vit. E was discovered in vegetable oils

necessary for reproduction in rats and named

this antisterility factor ± tocopherol.

E-Tocopherol is the only one with vit. E

activity in the human body. The other

tocopherols are not readily converted to E-

tocopherol in the body, nor do they perform the

same roles.

RD A : 15 mg/day

Antioxidant (stabilization of cell membranes,

regulation of oxidation reactions, protection of

PUFA and vit. A)





Deficiency Disease and Symptoms diseases of fat malabsorption such as cystic fibrosis

RBC breakage

neuromuscular dysfunction involving the spinal cord and retina

common symptoms include loss of muscle coordination and

reflexes and impaired vision and speech

Toxicity

rare

extremely high dose of vit. E may interfere with blood-clotting action

of vit. K and enhance the effects of drugs used to oppose blood clotting

causing hemorrhage.





Vitamin K Vit. K can be obtained from a nonfood source.

Bacteria in the GI tract synthesize vit. K that the

body can absorb.

K stands for the Danish word koagulation

(³coagulation´ or ³clotting´)

AI Men : 120 Qg/day Women : 90 Qg/day

Synthesis of blood-clotting proteins and bone

proteins





Deficiency Disease and Symptoms Primary deficiency develops in response to an

inadequate dietary intake whereas a secondary

deficiency occurs for other reasons.

Antibiotics kill the vit. K-producing bacteria in

the intestine, and anticoagulant drugs interfere

with vit. K metabolism and activity.

Newborn infant s present a unique case of vit.

K nutrition because they are born with a sterile

intestinal tract, and vit. K-producing bacteria take

weeks to establish themselves. At the same

time, plasma prothrombin are low (this reduces

the fatal blood clotting during the stress of birth).

Toxicity

Toxicity is not common, and no

adverse effects have been reported

with high intakes of vit. K.





Water Water--SolubleSoluble

VitaminsVitamins





Vitamin B1 (Thiamin) Thiamin is the vitamin part of the coenzyme TPP

(Thiamin pyrophosphate), which assists in energy

metabolism.

reaction removes 1-C from pyruvate to make

acetyl CoA + CO2 and participates in a similar step in TCA cycle where it helps convert 5-carbon

compound to 4-carbon compound.

Thiamin occupies a special site on the membrane of

nerve cells.

RD A : Men: 1.2 mg/day Women: 1.1 mg/day





Deficiency Disease and Symptoms Causation: Inadequate intake, malnourished and homeless people, alcoholic person

Alcohol contributes energy, but provides few nutrients and often displaces food. In addition,

alcohol impairs thiamin absorption and enhances thiamin excretion in urine.

Beriberi, first observed in Indonesia when the custom of polishing rice became

widespread.

Wet beriberi : with edema

Dry beriberi : with muscle wasting, but no edema

Wernicke-Korsakoff syndrome : severe thiamin deficiency in alcohol abusers

Symptoms: nervous system damage as well as to the heart and other muscles,disorientation, loss of short-term memory, jerky eye movements, stagging gait, enlarged heart,

cardiac failure, muscular weakness, apathy, confusion, irritability, anorexia, weight loss





Vitamin B2 (Riboflavin)

Riboflavin serves as a coenzyme in many reactions,

FMN (Flavin mononucleotide) and FAD (Flavin

adenine dinucleotide), which can accept and then

donate 2 hydrogens in TCA cycle and delivers them to

the electron transport chain.

RD A : Men: 1.3 mg/day Women: 1.1 mg/day

The greatest sources of riboflavin come from milk

and milk products.





Deficiency Disease and Symptoms Riboflavin deficiency most often accompanies other nutrient deficiencies.

Ariboflavinosis : Inflammation of the membranes of the mouth (cheilosis), skin,

eyes, and GI tract, sensitivity to light, reddening of cornea, sore throat, painful

smooth, purplish red tongue (glossitis)





Vitamin B3 (Niacin) The name niacin describes 2 chemical structures:

nicotinic acid and nicotinamide.

The body can easily convert nicotinic acid to

nicotinamide, which is the major form of niacin in the

blood.

The 2 coenzyme forms of niacin, NAD (nicotinamide

adenine dinucleotide) and NADP (nicotinamide

adenine dinucleotide phosphate), participate in

numerous metabolic reactions.

Niacin can be made in the body from its precursor,

tryptophan.

RD A : Men: 16 mg NE/day Women: 14 mgNE/day 1 niacin equivalent; NE = 1 mg niacin

= 60 mg Trp





Deficiency Disease and Symptoms Diarrhea, abdominal pain, vomiting; inflamed, swollen, smooth, bright red tongue,

depression, apathy, fatigue, loss of memory, headache; bilateral symmetrical rash

on areas exposed to sunlight (pellagra)

Pellagra = pellis (skin)+ agra (rough)





Toxicity

Painful flush, hives, and rush (³Niacin flush´)

Excessive sweating

Blurred vision,

Liver damage

Impaired glucose tolerance





Biotin Biotin plays an important role in metabolism as a

coenzyme that carries activated CO2. This role is critical in

TCA cycle.

Biotin delivers one-carbon to pyruvate, thus replenishing

oxaloacetate. The biotin coenzyme also serves crucial roles

in gluconeogenesis, fatty acid synthesis, and the breakdown

of certain fatty acids and amino acids.

The 2 coenzyme forms of niacin, NAD (nicotinamide

adenine dinucleotide) and NADP (nicotinamide adenine

dinucleotide phosphate), participate in numerous

metabolic reactions.

Niacin can be made in the body from its precursor,

tryptophan.

RD A : Adults : 30Qg/day

1 niacin equivalent; NE = 1 mg niacin

= 60 mg Trp





Deficiency Disease and Symptoms Depression, lethargy, hullucinations, numb or tingling sensation in the arms and

legs,

Red scaly rash around the eyes, nose, and mouth

hair loss





Vitamin B6 (pyridoxine)

occur in form pyridoxal and pyridoxamine.

they can be converted to the coenzyme PLP

(pyridoxal phosphate), which is active in amino

acid metabolism The conversion of the amino acid, Trp to niacin

or to the neurotransmitter, serotonin also depend

on PLP as does the synthesis of heme, nucleic

acids and lecithin.

RD A : Adults (19-50 y): 1.3 mg/day





Deficiency Disease and Symptoms Scaly dermatitis, anemia (small-cell type), depression, confusion, abnormal brain

wave pattern, convulsions

Toxicity

depression, fatigue, irritability, headaches, nerve damage causing

numbness and muscle weakness leading to an inability to walk and

convulsions, skin lesions





Vitamin B9 (folate, folic acid, folacin)

Pteroylglutamic acid (PGA)

Its primary coenzyme form, Tetrahydrofolate

(THF), serves as part of enzyme complex that

transfer one-carbon units that arise during

metabolism.

This action helps convert vit. B12 to one of its

coenzyme forms and helps synthesize the DN A

required for all rapidly growing cells.

RD A : Adults: 400 Qg/day





Deficiency Disease and Symptoms Anemia (large-cell type)

smooth, red tongue

Mental confusion, weakness, fatigue, irritability, headache

Toxicity

mask vit. B12-deficiency symptoms



D t t f Bi h i t





Deficiency Disease and Symptoms Anemia (large-cell type)

degeneration of peripheral nerves progressing to paralysis

Mental confusion, weakness, fatigue, irritability, headache

Department of Biochemistr





Vitamin C (ascorbic acid)

250 years ago, any man who joined the crew of a seagoing

ship knew he had at best a 50-50 chance of returning alive-not

because he might be slain by pirates or die in a storm, but

because he might contract the dread disease scurvy.

Only men on short voyages, especially around the

Mediterranean Sea, were free of scurvy.

The antiscurvy in limes and other foods was dubbed the

antiscorbutic factor .

Nearly 200 years later, the factor was isolated and found to be

a 6-carbon compound similar to glucose; it was names ascorbic

acid.

RD A : Men: 90 mg/day Women: 75 mg/day

smoker: +35 mg/day






Deficiency Disease and Symptoms Scurvy

Anemia (small-cell type)

Atherosclerotic plaques

Pinpoint hemorrhages

Bone fragility, joint pain

Frequent infections

muscle degeneration and pain

Toxicity Nausea, abdominal cramps, diarrhea, headache, fatigue, insomnia,

hot flashes, rashes

vitamins 2553 chatchawin

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