Vitamins(Biochemistry), Study notes of Chemistry

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ASCORBIC ACID(VITAMIN C):

 Vitamin C is water soluble, white crystalline,odourless substance with a sour taste  Fresh fruits and vegetables are efficient sources of vitamin C.Guava,citrus fruits and tomatoes are best sources  Biochemical role of ascorbic acid:  Ascorbic acid is involved in conversion of proline present in procollagen to hydroxyproline.This hydroxylation of proline is essential because in its absence collagen cannot form the triple helix required for the normal tissue structure

 EXCRETION : It is excreted in urine as such and as its derivates,i.e dehydroascorbic acid and diketogulonic acid

 Effects of Deficiency…..Scurvy : Scurvy is liable to occur in artificially-fed infants because of low vitamin C content

 Breast fed infants rarely suffer from scurvy

 Scurvy which is potentially fatal disease has following clinical picture,

 Disruption of adventitia,media,and basal laminae of blood vessels

 Anemia,weakness,tendency to remain motionless

 Skin shows hemorrhages

 At the growing ends of long bones osteoblastic function is arrested

 Delayed healing of wounds and fractures

THIAMINE(Thiamin):

(Aneurine,Vitamin B1,Anti-

Neuritic or Anti-beriberi factor)

 It is white, crystalline compound, very soluble in water

 It has an odor like that of yeast

 Thiamine has a pyrimidine and a thiazole part in its molecule which are linked by a methylene bridge

 Best dietary sources are whole grains,legumes,beef,liver,nuts,yeast

 Thiamine forms the coenzyme thiamine diphosphate also called thiamine pyrophosphate

RIBOFLAVIN(Vitamin B2):

 It is water soluble, orange crystalline compound

 Liver, wheat germs,yeast,milk,meats,fish and eggs are best sources

 It is absorbed from the upper GIT by a specific transport mechanism, only 9% appears in urine but urinary excretion increases with a greater intake

 Biochemical role: Riboflavin forms two coenzymes, riboflavin monophosphate usually called flavin mononucleotide(FMN) and flavin adenine dinucleotide(FAD)

 Deficiency Symptoms :

 Inflammation of lips

 There is scaliness and greasiness along with fissures in the folds of thee nose and ears

 Eye disturbances like inflammation and vascularization of cornea, redness of eye,photophobia,burning and drying of eyes

 The bone marrow shows erythroid hyperplasia

 Neuropathy

 Laboratory Tests for riboflavin deficiency :There is decreased activity of the FAD-containing enzyme glutathione reductase in the RBCs.The urinary content of riboflavin is also found to be low.

 Biochemical role: Nicotineamide is the part of structure of two coenzymes.NAD+ and NADP+,whose roles as coenzymes in biological oxidation

 Effects of Deficiency…..Pellagra: In man, pellagra which means rough skin,occurs.The disease is mostly found in women of child-bearing age and in growing children

 Following body systems are affected in pellagra,

 Skin

 Digestive system

 Nervous system

 The dietary requirement of this vitamin is less if good quality proteins are eaten because these provide Tryptophan which can form nicotine amide

PYRIDOXIN(Vitamin B6)

 Pyridoxine is water soluble, heat stable, basic substance with colorless crystals.  It is convertible to its aldehyde form,pyridoxal and amino form,pyridoxamine  Egg yolk,meat,fish and milk,yeast,whole grains are good sources of this vitamin  Biochemical role of vitamin B6 :  Transamination  Decarboxylation  It is a coenzyme for diamine oxidases which catalyze the oxidative deamination of diamines  It takes part in the the metabolism of tryptophan  Involved in the formation of niacin from tryptophan  It takes part in the metabolism of S-containing amino acids

PANTOTHENIC ACID:

 It is a viscous yellow oil, stable to moist heat, available commercially as sodium and calcium salts

 It occurs specially in liver,kidney,egg,milk,peas,cauliflower,potatoes

 The intestinal E.Coli also synthesize it which may be absorbed

 Biochemical Role: Pantothenic acid is first changed in the body to 4-phosphopantetheine by phosphorylation and linkage to thioethanolamine which forms a part of the molecule of coenzyme A.Coenzyme A is concerned with metabolism of proteins, fats and carbohydrates

 Pantothenic acid also occurs in the molecule of acyl carrier protein(ACP) which takes part in the biosynthesis of fatty acids

 Human Deficiency :

 Irritibality,restlesness,disturbesd sleep rhythm

 GIT disturbances

 Burning feet syndrome

 The following reactions need biotin as a coenzyme,

 1) Conversion of acetyl-CoA to malonyl-CoA.This is the first step in the cytoplasmic biosynthesis of fatty acids

 2) Conversion of pyruvic acid to oxaloacetic acid(pyruvic carboxylase)

 3) Carboxylation of propionic-CoA to D-methylmalonyl- CoA

 Conversion of B-methylcrotonyl-CoA to B- methylglutaconyl-CoA

 Clinical deficiency :

 Perioral dermatitis,Conjunctivitis,alopecia,ataxia

 Biotin is given therapeutically to babies with infantile Diarrhea, individuals with genetic alterations of biotin- dependent enzymes

FOLIC ACID:(PTEROYLMONOGLUTAMIC

ACID:PGA)

 Folic acid is yellow crystalline substance and is only slightly soluble in water

 Its structure has three components---a derivative of pteridine,para-aminobenzoic acid(PABA) and Glutamic acid

 It is named folic acid because it occurs especially in the foliage of plants

 It s chief dietary sources are liver,kidney,beef,cauliflower and wheat

 It is stored in the liver, of the total body folic acid which is 6 to 10 mg,upto 6O% is present in the liver

 Effects of folic acid deficiency: Blood shows macrocytic anemia,Megaloblastic anemia  Gonadal failure leading to azoospermia in males and amenorrhea in females  Children born to folic acid deficient mothers show neural tube defects,e.g.spina bifida  Clinical deficiency of folic acid :  Inadequate intake  Malabsorption

 Impaired metabolism  Increased requirement  Laboratory Tests for Folic Acid deficiency:  FIGLU test(Formiminoglutamic acid)

 Serum and erythrocyte concentration of folic acid is low

 Clinical uses of folic acid:

 It is very useful in certain macrocytic anemias

 It can also restore normal hematopoiesis in pernicious anemia

 It is used along with vitamin B6 and B12 to lower plasma homocysteine,the raised level of which is a risk factor for ischemic heart disease