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PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN VITAMIN B-6 PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Introduction Vitamin B6 is actually a collective term for three naturally occurring pyridines that are functionally and metabolically related: Pyridoxine Pyridoxal Pyridoxamine Discovered during Nutritional studies on rats in 1930 PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Chemical structure Pyridoxal Pyridoxine or Pyridoxol 2 Methyl.3 hydroxy,4,5 dihydroxymethyl pyridine Pyridoxamine PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Active forms are: Pyridoxal Phosphat Aldehyde group at position 4 can reversibly attach with NH3. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Food sources Found in wide varieties of foods. Beans, Legumes and nuts Eggs,Meats ( beef,chicken breast) Fish (Trout,Salmon, tuna) Bread and cereals Spinach and tomato Banana PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Functions Vitamin B6 is involved in variety of metabolic processes. Plays a major role in amino acid metabolism Trasamination Decarboxylation Transulfuration PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Functions Needed for conversion of Tryptophan to niacin Formation of melanin Breakdown of glycogen to glucose Inter conversion of glycine and serine where it functions along with Folic Acid. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Absorption and Metabolism Readily absorbed from intestine. In cytoplasm it is converted into Pyridoxal phosphate and pyradoxalamine Phosphate by pyridoxal Kinase and ATP. These are the active forms of the vitamin. Mainly found in extra-cellular fluid PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Concentration is relatively high in Leukocytes Nerve tissues and Liver As water soluble, very little is stored and Any excess, is excreted in urine in the form of pyridoxic acid. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Recommended Daily Allowances The daily requirements of Vitamin B6 Directly related to protein intake RDA 2.2 mg for men and 2 mg for women. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Effects of Deficiency After prolong deficiency is commonly seen in pregnant women and infants. Dermatitis Glossitis Blood disorders PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Dermatitis PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Seborrheic dermatitis PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Cheilosis Angular stomatitis Peripheral neuropathy and PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Toxic Effects Very limited toxicity in humans PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN FOLIC ACID FOLACIN Vit.B 10 PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN STRUTURE Folic acid is a conjugated molecule consisting of a pteridine ring structure linked to para-aminobenzoic acid (PABA) that forms pteroic acid. Folic acid itself is then generated through the conjugation of glutamic acid residues to pteroic acid PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Folic Acid positions 7 & 8 carry hydrogens,in Dihydrofolate (DHF) positions 5-8 carry hydrogens, in Tetrahydrofolate (THF) PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Folacin is generic name for folic acid and related compounds. The chemical term for folacin or folic acid is pteroylglutamic acid. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Food Sources The richest sources of folacin include Liver Spinach Wheat Yeast and Dry beans Almost all deep green leafy vegetables are also good sources of this vitamin PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Absorption and Metabolism Plants Folic Acid contains 7 or 5 Glutamyl Residues linked together by a peptide bond. The peptide bond is hydrolyzed by intestinal enzymes and the compound with one glutamyl residues is formed Folic acid in the form of its monoglutamyl form is absorbed only. Then it is reduced to tetrahydrofolate in the intestinal mucosa during absorption. Vitamin C is required for this reduction PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN All forms of folacin are equally utilized in the body More folacin is excreted in urine and feces than is accounted for in the diet, which indicates that this vitamin is also synthesized by intestinal flora Most of folacin is stored in liver Folic acid is converted to its biologically active form folinic acid in the liver PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Recommended dietary allowance RDA for adults in 400 g of folacin daily PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Deficiency Diseases Folate deficiency results in complications nearly identical to those of vitamin B12 deficiency. The most pronounced effect of folate deficiency on cellular processes is upon DNA synthesis. The result is megaloblastic anemia as for vitamin B12 deficiency. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Megaloblastic anemia PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Deficiency Diseases The inability to synthesize DNA during erythrocyte maturation leads to abnormally large erythrocytes termed macrocytic anemia. Folate deficiencies are rare due to the adequate presence of folate in food. Poor dietary habits as those of chronic alcoholics can lead to folate deficiency. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Deficiency Diseases The predominant causes of folate deficiency in non-alcoholics are impaired absorption or metabolism or an increased demand for the vitamin. Certain drugs such as anticonvulsants and oral contraceptives can impair the absorption of folate. Anticonvulsants also increase the rate of folate metabolism. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Deficiency Diseases Folic acid appears to reduce the risk of stroke Low blood levels of folic acid are associated with increased risk of cancer. (Breast, pancreas and colon) Damage to DNA caused by folate deficiency may be the reason. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Prevention of Neural Tube Defect leading to spina bifida at the very early stage of pregnancy PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN INCREASED REQUIREMENT The predominant condition requiring an increase in the daily intake of folate is, pregnancy. pregnancy and infancy are both characterized by increased number of rapidly proliferating cells present in the blood. The need for folate will nearly double by the third trimester of pregnancy. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Possible Toxic Effect Risk from Folic acid Toxicity is very low. Tolerable upper intake level for adult is 1 mg/day. Upper intake level is 800 ug/day for pregnant and lactating women if less than 18 years of age. Supplemental level should not increase than the upper level to prevent folic acid from masking symptoms of Vitamin B-12 PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Vitamin B12 PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Introduction Vitamin B12 includes a group of cobalt, containing compounds known as cobalamins. The major forms found in plasma and tissue include Methyl cobalamin Adenolylcobalmin and Hydroxycobalamin. All of these forms are biologically active. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Food sources Vitamin B12 occurs only in animal sources. The richest sources include Lamb and beef kidney Lamb and calf beef Liver and brain. Other good sources include Heart, egg yolk and variety of sea foods PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Stability and solubility Stable to heat in aq.medium Only slightly soluble in water It is destroyed by strong acid and Alkalies Little lost during cooking PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Functions Vitamin B12 is required by all cells of the body, especially Gastro-intestinal tract Bone marrow and Nervous system. Within bone marrow, it is involved in conversion of ribose nucleotides into deoxyribose nucleotides PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Functions (Contd.) An essential step in DNA synthesis. If DNA is not synthesized in enough quantities, large RBC’s (macrocytes) are released into the blood. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Absorption and Metabolism Vitamin B12 is absorbed through receptor sites in the ileum, mediated by intrinsic factor which is produced by glands in stomach. Vitamin is then transported across the intestinal cell and then into blood stream. Vitamin B12 is normally stored in liver for 3 to 5 years. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Recommended Dietary Allowances The RDA of 3.0 g of Vitamin B12 for adults allows for maintenance of adequate nutrition and substantial reserve body pool. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Effects of Deficiency Deficiency of Vitamin B12 is usually caused by defect in absorption rather than by dietary factors When intrinsic factor is not produced, Vit B12 is not absorbed. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Effects of Deficiency (Contd.) As a result, bone marrow cannot produced mature red blood cells and so releases the large, immature precursor (macrocytes) into blood stream instead. The symptoms of megalotblastic anemia include pallor, weight loss, anorexia, glossitis, sprue and in advanced stages, degeneration of spinal cord. PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN Toxic Effect No toxic effect in humans PESHAWAR MEDICAL COLLEGE NWFP PAKISTAN