water soluble vitamins - vitamin B complex

what are the members of the vitamin B complex?

1. thiamin (B1)

2. riboflavin (B2)

3. niacin (B3)

4. pyridoxine (B6)

5. biotin (B7)

6. folic acid (B9)

7. cyanocobalamin (B12)

8. pantothenic acid (B5)

B4, B8, B10 and B11 do not fit the criteria for vitamin status and thus are not considered a part of the vitamin B complex

what is vitamin B1 alternate name?

thiamin

what is vitamin B2 alternate name?

riboflavin

what is vitamin B3 alternate name?

niacin

what is vitamin B5 alternate name?

pantothenic acid

what is vitamin B6 alternate name?

pyridoxine

what is vitamin B7 alternate name?

biotin

what is vitamin B9 alternate name?

folic acid

what is vitamin B12 alternate name?

cyanocobalamin

chemistry of thiamin

• heat labile sulfur containing vitamin

• contains a pyrimidine ring and thiazole ring which are joined by a methylene bridge

• highly alkaline sensitive

absorption and transportation of thiamin

absorbed in small intestine by active transport mechanism and simple diffusion, then it reaches the liver through circulation

function of thiamin

• thiamin pyrophosphate (TPP or TDP) is the active form of thiamin

• formed from thiamin in the presence of ATP in a reaction catalyzed by thiamin kinase present in the liver

• TPP is the prosthetic group of enzymes like:

  • pyruvate dehydrogenase

  • α-keto glutarate dehydrogenase, etc.

what are some sources of thiamin?

rich sources:

• outer coatings of food grains like rice, wheat and yeast

good sources

• whole cereals, pulses, oilseeds and nuts

fair sources

• meat, liver, egg and fish

what are some things thiamin deficiency can cause?

• adult beriberi, which is further spilt into

  • wet and dry beriberi

• infantile beriberi

what are early signs of adult beriberi?

• insomnia

• headaches

• dizziness

• loss of appetite

• muscle weakness

• numbness

• prickling sensation in lower limbs

• fatigue

what can adult beriberi lead to if not treated?

1. wet beriberi

2. dry beriberi

what is wet beriberi?

• in which the cardiovascular system is affected and it is characterized by edema

• edema appears in the lower limbs, trunk, face and serous cavities. blood pressure becomes abnormal, and the heart becomes weak, which can lead to death through heart failure

what is dry beriberi?

• in which the central nervous system is affected

• in addition to early signs of adult beriberi, severe muscle wasting occurs

• as a result, the individual is unable to walk and becomes bed ridden. death may occur if left untreated

what is infantile beriberi?

in infants, thiamin deficiency causes infantile beriberi. it occurs in infants between 2-10 months of age

chemistry of riboflavin

• contains a heterocyclic isoalloxazine ring and a ribitol (a sugar alcohol)

• sensitive to ligh and alkali, but stable to heat and acidic mediums

what can a riboflavin deficiency cause?

in humans, riboflavin deficiency can cause oral, facial, and ocular lesions

what oral lesions are caused by riboflavin deficiency?

• angular stomatitis, which are lesions of the mouth, particularly at the corners of the mouth

• glossitis, which is an inflamed, magenta colored tongue

what facial lesions are caused by riboflavin deficiency?

cheilosis, which is red, swollen and cracked lips

what ocular lesions are caused by riboflavin deficiency?

vascularization of the cornea and conjunctiva and bloodshot eyes

chemistry of niacin

• the word niacin refers to two pyridine derivatives, which are:

  1. nicotinic acid

  2. nicotinamide

• both are highly stable to heat and stable to alkali and acid

absorption and transportation of niacin

nicotinic acid and nicotinamide are absorbed in the small intestine and reach various tissues through circulation, which they are then converted into NAD and NADP

functions of niacin

• nicotinamide is a component of two enzymes, NAD and NADP.

• NAD is nicotinamide adenine dinucleotide

• NADP is nicotinamide adenine dinucleotide phosphate

sources of niacin

• whole grains, peanuts, legumes, yeast, liver, fish and met are good sources

• milk and egg are poor sources but a rich source of tryptophan

• vegetables and fruits are also a poor source

what can a niacin deficiency cause?

• it can cause pellagra, in which skin, gastrointestinal tract and nervous system are affected

• dermatitis, diarrhea and dementia are characteristic symptoms of pellagra

chemistry of pyridoxine

• three compounds derived from pyridine that show vitamin B6 activity. they are:

  1. pyridoxine

  2. pyridoxal

  3. pyridoxamine

• it is stable to heat and sensitive to light and alkali

absorption and transportation of pyridoxine

• easily absorbed and reaches various tissues through circulation

• in the tissues, pyridoxine is converted into pyridoxal and pyridoxamine

functions of pyridoxine

• pyridoxal phosphate is the active form. it is formed when pyridoxal by phosphorylation is catalyzed by pyridoxal kinase

• pyridoxal phosphate acts as a prosthetic group / coenzyme of enzymes, which are involved in transamination, decarboxylation, transsulfuration, desulfuration and non-oxidative deamination occurs

• pyridoxal phosphate is also a coenzyme for enzymes that are involved in the synthesis of heme, serotonin, catecholamines and coenzyme A synthesis

sources of pyridoxine

• whole grains, legumes, liver and yeast are good sources

• leafy vegetables, milk, meat and eggs are fair sources

pyridoxine deficiency

1. rare in human adults

2. in children, it causes epileptic form of convulsions (seizures) due to decreased formation of neurotransmitters like GABA, serotonin and catecholamines

chemistry of biotin

• sulfur containing vitamin

• consists of imidazole ring that is fused to a tetrahydro thiophene with a valerie acid side chain

• stable to heat, but alkaline sensitive

absorption and transportation of biotin

• absorbed in the small intestine and reach the liver and other tissues through circulation

function of biotin

• prosthetic group of several carboxylases like pyruvate carboxylase, acetyl-CoA carboxylase, propionyl-CoA carboxylase, etc

• attached to e-amino groups of lysyl residue of apoenzyme through amide linkage

• in carboxylation reactions, it acts as a carrier of CO2

dietary sources of biotin

• whole cereals, legumes, groundnuts, milk, meat and fish are good sources

• vegetables and fruits are fair sources

biotin deficiency

rare in humans because it is present in most common foods

chemistry of folic acid

• consist of pteridine nucleus, p-aminobenzoic acid and glutamate.

• sensitive to light and acid but stable to heat alkali

absorption and transportation of folic acid

• present in natural foods

• is called foly polyglutamate

• in the intestinal mucosal cells hydrolase, form folic acid which is reduced to N5-methyl tetrahydrofolate

• methy tetrahydrofolate is the major circulating form, bound to protein

function of folic acid

• tetrahydrofolate or FH4 which is reduced form of folic acid, and is the carrier of one carbon units

• required for synthesis of DNA through nucleotides, particularly TMP formation, in rapidly dividing cells like bone marrow or erythropoietic or intestinal cells

• folic acid prevents neural tube defects (NTD) that occur during fetal development

sources of folic acid

• green leafy vegetables, pulses, egg and liver are good sources

• coconuts, whole cereals and milk are fair sources

folic acid deficiency

• megaloblastic anemia is the main symptom and is most common in pregnant women and in unweaned children

chemistry of cyanocobalamin

• complex chemical structure

• tetrapyrrole ring system called corrin ring

absorption and transportation of cyanocobalamin

• absorption of vitamin B12 takes place in ileum.

• transcobalamin I delivers B12 to the tissues

storage of cyanocobalamin

unlike other water soluble vitamins, B12 is stored in the liver and other tissues

function of cyanocobalamin

acts as prosthetic group or coenzyme

deficiency of cyanocobalamin

• affects bone marrow, intestinal tract and neurological system.

• they are affected because DNA synthesis, methionine synthesis and fatty acid synthesis are altered

chemistry of pantothenic acid

• it is an amide of beta alanine and dihydroxy dimethyl butryic acid (pantoic acid)

• stable to heat but unstable to alkali or acid

absorption and transport of pantothenic acid

• intestinal phosphatases release pantothenic acid from dietary sources

• free pantothenate or its salts are freely absorbed in the intestine and reach various tissues through circulation

functions of pantothenic acid

• a component of coenzyme A. coenzyme CoA participates in several enzymatic reactions of carbohydrates, lipids, and amino acid residues

• serves as carrier of acyl groups during fatty acid biosynthesis

deficiency of pantothenic acid

causes burning feet, abdominal cramps, restlessness and fatigue in humans

sources of pantothenic acid

• organ meat, liver, milk, whole cereals, legumes and eggs are good sources

• vegetables and fruits are poor sources