2 Water soluble vitamins.pptx

nutrition

1. Water Soluble Vitamins

2. Vitamins Organic compounds occurring in natural foods either as such or as utilizable precursors Required in minute amounts for normal growth, maintenance and reproduction They differ from other organic food stuffs in that: • They do not enter into tissue structures, unlike proteins. • Do not undergo degradation for providing energy unlike carbohydrates and lipids. They differ from hormones: In not being produced within the organism, and most of them have to be provided in the diet History: The protective substances present in milk were named as accessory factors by Hopkins. Almost in the same year, Funk (1911–12) isolated from rice polishings a crystalline substance which could prevent or cure polyneuritis in pigeons. Chemically it was found to be an amine and as it was vital to life, he named it as vitamine .

3. Classification All vitamins are broadly divided into two groups according to solubility. 1. Water-soluble Vitamins (a) Vitamin C (ascorbic acid), (b)Vitamin B complex group includes: • Vitamin B1 (thiamine) • Vitamin B2 (riboflavin) • Niacin (nicotinic acid) • Vitamin B6 (pyridoxine)• Pantothenic acid • α- Lipoic acid • Biotin • Folic acid group • Vitamin B12 (cyanocobalamin). Other water-soluble vitamins included in this group are: • Inositol • Para-amino benzoic acid (PABA) • Choline. 2. Fat-soluble Vitamins • Vitamin A • Vitamin D Vitamin E, and • Vitamin K.

4. Biological Importance Most of the water soluble vitamins function as coenzymes or prosthetic groups of several enzymes involved in carbohydrate, lipid and amino acid metabolism etc. Deficiency of water soluble vitamins produce beriberi, glossitis, pellagra, microcytic anaemia , megaloblastic anaemia and scurvy. Some vitamin analogs are used as drugs. For example folic acid analogs are used as anticancer agents and antibiotics. Moderate consumption of some vitamins is found to decrease occurrence or severity of some diseases. For example carotenes, Vitamin E and Vitamin D consumption at moderate level reduces incidence of cancer and cardiovascular diseases. Consumption of vitamin C in significant amounts reduces severity of cold. They slow down ageing process also. Vit B12, Folic acid and Vit B6 are beneficial to coronary artery disease patients. They lower plasma homocysteine levels

5. WATER-SOLUBLE VITAMINS VITAMIN C (ASCORBIC ACID) Chemistry • Synonyms: Antiscorbutic vitamin It is a sugar acid known as hexuronic acid. Ascorbic acid is an enediol-lactone of an acid with a configuration similar to that of the sugar L-glucose D-forms are generally inactive as anti-scorbutic agent. Naturally occurring vitamin C is L-Ascorbic acid. Ascorbic acid is easily oxidized by atomospheric O2 to dehydro ascorbic acid

6. Biosynthesis: Some lower mammals like rats can synthesize the vitamin from glucose by the uronic acid pathway. Man, monkey and guinea pigs lack the enzymes necessary for the synthesis They cannot convert ketogulonolactone to ascorbic acid. Hence the entire human requirement must consequently be supplied by the diet. Normal human blood plasma: It contains approx. 0.6 to 1.5 mg of ascorbic acid per 100 ml. The vitamin exists in the body largely in the ‘reduced’ form, with reversible equilibrium with a relatively small amount of “dehydroascorbic acid” (oxidized form). Both forms are physiologically and metabolically active. Under normal dietary intake (of 75 to 100 mg) 50 to 75% are converted to inactive compounds 25 to 50% is excreted in urine as such. It is also secreted in milk.

7. Metabolism: Absorption, distribution and excretion It is absorbed readily from the small intestine, peritoneum and subcutaneous tissues. It is widely distributed throughout the body. Some tissues contain high concentrations as compared to others. Local concentration roughly parallels the metabolic activity, found in descending order as follows: Pituitary gland, adrenal cortex, corpus luteum, Liver, brain, gonads, thymus, spleen, kidney, heart, skeletal muscle, etc. From maternal blood, it can cross the placental barrier and supplies the foetus . Metabolites (a) Chief terminal metabolites in the rat and guinea pig are CO2 and oxalic acid. (b) In human beings, decarboxylation of Ascorbic acid does not occur, the chief terminal metabolites being, oxalic acid and diketogulonic acid, which are excreted in urine.

8. Occurrence and food sources : Widely distributed in plants and animal tissues. In animal tissues, no storage, contains small amount, but highest concentration in metabolically highly ‘active’ organs, e.g. adrenal cortex, corpus luteum, liver, etc. Dietary sources: These are chiefly vegetable sources. Good sources are citrous fruits—orange/lemon/lime, etc ; other fruits like papaya, pineapple, banana, strawberry. Amongst vegetables—leafy vegetables like cabbage and cauliflower, germinating seeds, Green peas and beans, potatoes, and tomatoes. Amla is the richest source. Considerable amount of vitamin C activity is lost during cooking, processing and storage, because of its water-solubility and its irreversible oxidative degradation to inactive compounds.

9. Functions of Vitamin C Ascorbic acid act as antioxidant. It is free radical scavenger. Since it is a strong reducing agent it protects carotenes, vitamin E and other B vitamins of dietary origin from oxidation. It is required for the hydroxylation of proline and lysine residues of collagen. Since collagen is component of ground substance of capillaries, bone and teeth, so vitamin C is required for proper bone and teeth formation also. It participates in hydroxylation reactions of steroid biosynthesis. It is required for catecholamine synthesis from tyrosine. In the liver bile acid synthesis requires ascorbic acid. It is required for the absorption of iron in the intestine. It maintains iron in ferrous form. Catabolism of tyrosine (meat, egg fish) requires ascorbic acid.

10. Vitamin C deficiency In adults deficiency of vitamin C causes scurvy. But it rarely occurs in normal people. The symptoms of scurvy are (a) Haemorrhages in various tissues particularly in inside of thigh, calf and forearm muscles. It may be due to capillary fragility. (b) General weakness and anaemia . (c) Swollen joints, swollen gums and loose tooth. (d) Susceptible for infections. (e) Delayed wound healing. (f) Bone fragility and osteoporosis. Vitamin C deficiency in infants gives rise to infanitle scurvy. It occurs in weaned infants who are fed on diets low in vitamin C. Hypervitaminosis Administration of large amounts of ascorbic acid are not known to produce any effects in humans. But in rats, dehydroascorbic acid in enormous doses (1.5 gm/kg body wt ) produces permanent diabetes, similar to that produced by the glycoside alloxan; it produces probably destruction of β -cells of islets of Langerhans. This action is prevented by immediate antecedant IV injection of – SH compounds like cysteine, Glutathione as in the case of alloxan, which resembles dehydroascorbic acid in chemical structure.

11. VITAMIN B COMPLEX (THIAMIN-B1) Synonyms : Antiberiberi factor, antineuritic vitamin, aneurin . It is a heat labile sulfur containing vitamin. It contains pyrimidine ring and thiazole ring which are joined by methylene bridge. It is highly alkaline sensitive. Absorption and Transport : It is absorbed in small intestine by active transport mechanism and simple diffusion. Then it reaches liver through circulation. THIAMIN Function   Thiamin pyrophosphate (TPP or TDP) is the active form of thiamin. which  functions  as a  coenzyme  in the metabolism of carbohydrates, lipids, and branched-chain amino acids. TPP is the prosthetic group of enzymes like pyruvate dehydrogenase, α-keto glutarate dehydrogenase etc. It is involved in decarboxylation of α- keto acids during adenosine triphosphate (ATP) synthesis and maintenance of reduced glutathione in erythrocytes THIAMIN Sources Rich Sources. Outer coatings of food grains like rice, wheat and yeast. Good sources. Whole cereals, pulses, oilseeds and nuts. Fair sources. Meat, liver and egg and fish.

12. Biosynthesis: Synthesized by plants, yeasts and bacteria. Not synthesized by human beings, hence should be supplied in diet. Intestinal bacterial flora can synthesize the vitamin. Thiamine Deficiency Thiamine Deficiency If not treated it leads to Adult beriberi. Early signs of beri beri are insomnia, headache, dizziness, loss of appetite, muscle weakness, numbness and pricking sensation in lower limbs and fatigue. Infantile beri beri . In infants thiamine deficiency causes infantile beri beri . It occurs in infants between 2-10 months of age. Wet beri beri . In which cardiovascular system is affected and it is characterized by edema ( Edema ( swelling) happens when your small blood vessels leak fluid into nearby tissues). Edema appears in lower limbs, face and serous cavities. Blood pressure becomes abnormal. Heart becomes weak and death occurs due to heart failure. Dry beri beri . In which central nervous system is affected. In addition to early signs severe muscle wasting occurs. As a result individual is unable to walk and becomes bed ridden. Death may occur if not treated. Storage: Capacity to store is limited. It is present in both free and combined forms in heart (highest concentration), Liver and kidneys. In lower concentration in skeletal muscle and brain. Total amount of Thiamine in body is approx. 25 mg.

13. Riboflavin (Vitamin B2) Chemistry Synonyms: Lactoflavin , ovoflavin , hepatoflavin It is an orange-yellow compound containing A ribose alcohol: D- Ribitol A heterocyclic parent ring structure Isoalloxazine (Flavin nucleus). 1-Carbon of ribityl group is attached at the 9 position of isoalloxazine nucleus. Ribityl is an alcohol derived from pentose sugar D-ribose. It is sensitive to light and alkali but stable to heat and acidic medium. Absorption and Transport Absorbed in small intestine and distributed to all tissues by circulation. Functions Active forms of riboflavin are FMN and FAD. They act as prosthetic groups of several enzymes. FMN is flavin mononucleotide and FAD is flavin adenine dinucleotide. They act as carriers of hydrogen atoms in redox reactions.

14. Biosynthesis: All higher plants can synthesise riboflavin. In nature, it occurs both as “free form” and also as “nucleotide” form or as flavoproteins. Human beings and animals cannot synthesise and hence solely dependant on dietary supply. In man, considerable amounts can be synthesised by intestinal bacteria, but the quantity absorbed is not adequate to maintain normal nutrition. Sources Whole grains, legumes, pulses, green leafy vegetables, yeast, eggs, milk and meat are good sources Root vegetables and fruits are fair sources. Deficiency In humans riboflavin deficiency causes oral, facial, occular lesions. (a) Angular Stomatitis. Lesions of mouth particularly at corners of mouth. (b) Cheliosis . Red swollen and cracked lips. (c) Vascularization of cornea and conjuctiva and blood shot eyes. (d) Glossitis. Inflammated magenta coloured tongue.

15. NIACIN-B3 Synonyms: Nicotinic acid, P-P factor, Pellagra-preventing factor Chemistry: Nicotinic acid (niacin) is chemically Pyridine 3-carboxylic acid. In tissues: Occurs principally as the amide (nicotinamide, niacinamide). In this form it enters into physiological active combination. Highly stable to heat and alkali and acid. Absorption and transport Nicotinic acid and nicotinamide are absorbed in small intestine and reach various tissues through circulation where they are converted to NAD and NADP. Functions Nicotinamide is component of two coenzymes NAD and NADP. NAD is nicotinamide adenine dinucleotide and NADP is nicotinamide adenine dinucleotide phosphate.

16. Biosynthesis: Amino acid tryptophan is a precursor of nicotinic acid in many plants, and animal species including human beings Intestinal bacteria: - It can be synthesized also by intestinal bacteria. Bacteria in addition to synthesis from tryptophan, can also synthesize from other amino acids, e.g. glutamic acid, proline, ornithine and glycine. In human beings: – In addition to dietary source, – It is synthesized in tissues from amino acid tryptophan, and – To a limited extent supplemented by bacterial synthesis in intestine. Sources Whole grains, peanuts, legumes, yeast, liver, fish and meat are good sources. Milk and egg are poor source of niacin but rich source of tryptophan. Vegetables and fruits are poor source of niacin. Deficiency causes pellagra in which skin, gastrointestinal tract and nervous system are affected. Dermatitis, Diarrhea and Dementia are characteristic symptoms of pellagra. In high corn diet, requirement of dietary niacin increases, as synthesis from tryptophan cannot take place. The reason is the maize protein Zein lacks the amino acid tryptophan. Hence pellagra is more common in persons whose staple diet is maize. Niacin toxicity: Excessive dosage can produce toxic effects: – Dilatation of blood vessels and flushing. – Skin irritation – Can produce liver damage

17. PYRIDOXINE-B6 Synonyms: Rat antidermatitis factor. Chemistry Three compounds derived from pyridine show vitamin B6 activity. They are pyridoxine, pyridoxal and pyridoxamine. Pyridoxine is stable to heat and sensitive to light and alkali. Absorption and Transport • Pyridoxine is easily absorbed and reaches various tissues through circulation. In the tissues pyridoxine is converted to pyridoxal and pyridoxamine. Functions Pyridoxal phosphate is active form. It is formed from pyridoxal by phosphorylation catalyzed by pyridoxal kinase. Pyridoxal phosphate act as prosthetic group or co enzyme of enzymes which are involved in transamination, decarboxylation, transsulfuration , desulfuration and non- oxidative deamination reactions. Pyriodoxal phosphate is coenzyme for enzymes that are involved in the synthesis of heme, serotonin, catecholamines and coenzyme A synthesis.

18. Vitamin B6 may cut risk of Parkinson’s Disease, Recently it has been claimed by Dutch researchers and reported in neurology that a higher intake of vitamin B6 may decrease the risk of Parkinson’s disease. It could lower Parkinson’s disease risk by protecting brain cells from damage caused by free radicals Sources Whole grains, legumes, liver and yeast are good sources. Leafy vegetables, milk, meat and eggs are fair sources. Pyridoxine Deficiency 1. It is rare in human adults. Deficiency In children vitamin B6 deficiency causes epileptic form convulsions (seizures) due to decreased formation of neuro transmitters like GABA, serotonin and catecholamines.

19. BIOTIN-B7 Chemistry It is a sulfur containing vitamin. It consist of imidozole ring fused to tetrahydro thiophene with valerie acid side chain. It is stable to heat but alkaline sensitive. Absorption and transport It is absorbed in the small intestine and reaches liver and other tissues through circulation. Function Biotin is prosthetic groups of several carboxylases like pyruvate carboxylase, acetyl-CoA carboxylase, propionyl-CoA carboxylase etc. In carboxylation reaction it acts as a carrier of CO2 sources Whole cereals, legumes, groundnuts, milk, meat and fish are good sources. Vegetables and fruits are fair sources. Deficiency Rare in humans because it is present in most of the common foods.

20. FOLIC ACID Chemistry Folic acid consist of pteridine nucleus, p-aminobenzoic acid and glutamate. It is sensitive to light and acid but stable to heat and alkali. Absorption and transport • Folic acid present in natural foods is called as folyl polyglutamate. In the intestinal mucosal cells hydrolase form folic acid which is reduced to N5 - methyl tetrahydrofolate. Methyl tetrahydrofolate is the major circulating form probably bound to protein. Function • Tetrahydrofolate or FH4 which is reduced form of folic acid is carrier of one carbon units. • Folic acid is required for the synthesis of DNA through nucleotides particularly TMP (thymidine mono phosphate) formation, in rapidly dividing cells like bone marrow or erythropoietic cells or intestinal cells. • Folic acid prevents neural tube defects (NTD) that occur during fetal development. Sources • Green leafy vegetables like spinach, cabbage, ladyfinger, curry and mint leaves, pulses like black gram, green gram, eggs and liver are good sources. Coconuts, whole cereals and milk are fair sources. Deficiency • Megaloblastic anaemia is the main symptom of folic acid deficiency. It is most common in pregnant women

21. CYANOCOBALAMIN (VITAMIN-B12) Chemistry • It has complex chemical structure. It is made up of Tetrapyrrole ring system called as corrin ring with a central cobalt (Co) atom with molecular formula (C63 H88 N14 O14 PCO) Absorption and Transport • The absorption of vitamin B12 takes place in ileum. Transcobalamin II delivers vitamin B12 to tissues. Storage • Unlike other water soluble vitamins vitamin B12 is stored in the liver and other tissues. Functions • Vitamin B12 act as prosthetic group or coenzyme. Deficiency • Vitamin B12 deficiency affects bone marrow, intestinal tract and neurological system. In vitamin B12 deficiency these systems are affected because DNA synthesis, methionine synthesis and fatty acid synthesis are altered.

22. PANTOTHENIC ACID Chemistry It is an amide of β- alanine and dihydroxy dimethyl butyric acid ( Pantoic acid) It is stable to heat but unstable to alkali or acid. Absorption and transport • 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 • Pantothenic acid is a component of coenzyme A. Coenzyme (CoA) participates in several enzymatic reactions of carbohydrate, lipid and amino acid metabolism. • It serves as carrier of acyl groups during fatty acid biosynthesis. Deficiency • It cause burning feet, abdominal cramps, restlessness and fatigue in humans. Sources • Organ meat, liver, milk, whole cereals, legumes and eggs are good sources. Vegetables and fruits are poor sources.