Vitamins
■ Vitamins are organic molecules that are essential for proper functioning and growth of the human body.
■ As many of these molecules perform the role of coenzymes and antioxidants in the human body.
■ Whole grains, green vegetables, fruits and animal products are rich sources of vitamins.
■A Polish biochemist Casimir Funk coined the term ‘vitamin’ in 1912 who designated it as essential factor for life (Vita means “important” and amine means “possessing amine group”).
■ All vitamins are not amines.
■ The structure of all vitamins contain hetrocyclic ring of hydrogen, nitrogen, carbon, oxygen.
Vitamins are classified into two broad categories on the basis of their solubility :
Water soluble vitamins
Fat soluble vitamins
Water soluble vitamins divided into two parts :
⦿ B-Complex vitamins
⦿ Ascorbic acid (Vitamin C)
⦿ B-Complex vitamins are:
Thiamin (Vitamin B1)
Riboflavin (Vitamin B2)
Niacin (Vitamin B3)
Partoethenic acid (Vitamin B5)
Pyridoxin (Vitamin B6)
Biotin
Folic acid
Cobalamin (Vitamin B12)
⦿ Ascorbic acid (Vitamin C)
Fat soluble vitamins are:
Vitamin A
Vitamin D
Vitamin E
Vitamin K
B-complex Vitamins
They serve as a coenzymes in many enzymatic reactions and help to release energy bymetabolizing food stuff in the human body.
Thiamin (Vitamin B1)
Thiamin is the first vitamin of B-complex group which was discovered in
people affected with beriberi disease.
It can be synthesized by bacteria, fungi and plants.
It is a colorless compound which is found in cereals, groundnuts, pistachios, walnuts, mustard seeds, soybean and capsicum.
Thiamin is converted into biologically active form, thiamin pyrophosphoate in the human body
The common symptoms are muscular weekness, loss of sensation, vomiting, confusion.
It mosly affects neurological and cardiovascular system.
Thiamine containing balanced diet or supplements require for the treatment of beriberi disease.
Riboflavin (Vitamin B2)
Riboflavin is the second vitamin in the the B-complex group known as vitamin B2. Yeast, milk, liver, eggs and leafy vegetables are good sources of this vitamin.
Riboflavin has intense yellow color and is widely used as a food additive.
Riboflavin involves in the metabolism of carbohydrates, lipids and amino acids.
FAD is a coenzyme which play a role in the transferring of electrons in many metabolic reactions.
It acts as electron carrier in oxido-reduction reactions of oxidative phosphorylation, fatty acid and amino acid catabolism and citric acid cycle.
Lack of riboflavin :-
Fatigue, slow growth; cheilosis, glossitis dry and scaly skin (seborrheic dermatitis), abnormal vision and corneal inflammation.
Niacin (Vitamin B3)
The term ‘Niacin’ is referred collectively to nicotinamide and nicotinic acid.
It is known as vitamin B3.
Niacin is the non-toxic derivative of the toxic tobacco alkaloid, nicotine.
The amide derivative (CO-NH2) of nicotinic acid is called nicotinamide.
Niacin was discovered as nutrient while studying pellagra disease.
It is synthesized from tryptophan (an amino acid). Peanuts, legumes, meat, eggs and milk are rich sources of niacin.
Deficiency disease :
Pellagra disease results from the deficiency of niacin.
The early symptoms are vague, weakness, anorexia, indigestion and dizziness.
Photosensitive dermatitis, skin infections and digestive problems which are associated with niacin or tryptophan deficiency.
Pantothenic acid (Vitamin B5)
Pantothenic acid is also known as vitamin B5 which was identified by Roger J. Williams in 1931.
It is the peptide of -alanine and pentoic acid Pantothenic acid has a central role in energy-yielding metabolism.
Body cannot synthesize pantothenic acid, we must obtain it from dietary sources like whole grains, broccoli, avocados, cereals and mushrooms.
Pantothenic acid involes in the formation of coenzyme A (A for acyl).
It also required
for the acetylation of choline to form the neurotransmitter acetylcholine in the
brain.
Deficiency disease :
Deficiency of pantothenic acid is often related to low energy-level symptoms including fatigue and weakness.
Pyridoxine (Vitamin B6)
This vitamin exists in three different forms -pyridoxine, pyridoxamine and pyridoxal.
It is found in eggs, liver, yeast, cereals, legumes and milk.
The structure of vitamin B6 possess single pyridine ring having hydroxyl goup in pyridoxine, an amino group in the pyridoxamine and aldehyde group in the pyridoxal.
Vitamin B6 plays an important role in the metabolism of amino acids, fatty acids, glycogen and also as a steroid hormone
Deficiency diseases :
The clinical signs and symptoms of pyridoxine deficiency include anemia, dermatitis, peripheral neuropathy, gastrointestinal disorders, nausea and vomiting.
Biotin
Biotin is a water soluble vitamin. It was isolated from the egg by Dutch biochemist Fritz Kogl in 1935 later named it as biotin.
It is necessary for cell growth, metabolism of lipids and amino acids.
Yeast, nuts, tomato, animal meat, and egg yolk are some of the well-known sources of biotin.
It is widely found in many food sources in the form of biocytin.
The structure of biotin consists of imidazole and thiophene ring along with a fatty acid side chain
Deficiency diseases:
The general deficiency symptoms of biotin include loss of appetite and growth; dermatitis, hair loss and thickening of bones.
Folic acid
The term, Folic acid is derived from Latin word ‘folium’ which stands for ‘leaf’. It is also known as pteroylglutamic acid or folacin.
Plants are a rich source of folic acid especially, spinach leaves.
Green vegetables, whole grains, cereals, yeast, soybean and eggs are some of the other important sources of this vitamin.
Folic acid consists of a pteridine ring, para-amino benzoic acid (PABA), and glutamic acid.
Tetrahydrofolate is active form of dietary folic acid.
It works closely with Vitamin B12 in the synthesis of blood cells (RBC) and the amino acid homocysteine.
Deficiency diseases:
The deficiency of folic acid affects the synthesis of nucleic acids and amino acids.
The deficiency of folic acid is most common in pregnant women.
The deficiency in either folic acid or vitamin B12 can lead to megaloblastic anemia which cause clinical
symptoms like weakness, fatigue, depression, breathing problems and fetal neural tube defect in pregnant womens.
Cobalamin (Vitamin B12)
Vitamin B12 contains cobalt metal ion in the center of coring ring hence known as cobalamin.
It is the heaviest (molecular weight = 1355.4kd) and most complex of all the vitamins.
Vitamin B12 consists of a class of chemically related compounds known as vitamers (exhibiting vitamin activity).
Neither plants nor animals are capable to synthesizing vitamin B12.
Bacteria have the enzymes required for the synthesis of vitamin B12.
Dietary sources of vitamin B12 are animal meat (espically liver), milk products, eggs and shellfish.
Vitamin B12 is required for the normal functioning of the brain, nervous system and formation of red blood cells
(RBCs).
Vitamin B12 requires the specific protein, intrinsic factor for its absorption in the human body.
Due to lack of this factor causes vitamin B12- deficiency in the human body.
Vitamin B12 is found as hydroxocobalamin in bacteria but it is converted intomethyl cobalamin and 5’-deoxyadenosylcobalamin in human body.
Vitamin B12 is composed of Cobalt ion (Co3+), corrin ring system.
Methyl cobalamin and adenosyl cobalamin are two coenzymes of Vitamin B12 which are involved in metabolism of amino acids and synthesis of hemoglobin.
Vitamin B12 acts as a coenzyme for two enzymes: methionine synthase and L-methylmalonyl-CoA mutase.
Deficiency diseases:
The major signs of vitamin B12 deficiency are pernicious anemia and neuropathy.
The pernicious anemia disease is characterized by low hemoglobin levels, decreased number of
erythrocytes and neurologicmanifestation.
Vitamin C (Ascorbic Acid)
It is also known as vitamin C. Unlike B-complex vitamins, vitamin C acts as an antioxidant molecule which also falls in the group of water soluble vitamins.
Citrus fruits, peanuts, tomatoes and green vegetables are rich sources of this vitamin.
The structure of vitamin C has six corbon atoms with hydroxyl groups that resemble a glucose to some extent.
It is synthesized in most of the animals
and plants but it cannot be synthesized by human body due to lack of an enzyme L-gulonolactone oxidase.
This vitamin occurs in two forms; L-ascorbic acid (reduced form) and L-dehydro ascorbic acid (oxidized form) in the cells.
Vitamin C serves as a water soluble antioxidant that involve in neutralising free radicals in the cells.
Vitamin C is required for the hydroxylation of proline and lysine for the formation of collagen in the skin.
It also involved in the metabolism of folic acid, tyrosine and tryptophan. Vitamin C helps in wound healing, bone and teeth formation, improving immunity and absorption of iron from the diet. It is also widely used as a food additive to prevent oxidation.
Deficiency diseases:
Vitamin C-deficiency causes scurvy disease in humans.
Fragility of blood capillaries, bleeding from gums and tooth loss are common symptoms of Scurvy.
FAT-SOLUBLE VITAMINS
Fat-soluble vitamins are soluble in fat. Vitamins A, D, E and K are collectively known as fat soluble vitamins.
These vitamins stored in liver and adipose tissue and their requirement is something like “demand and supply”
Human body needs fat soluble vitamins to maintain healthy skin, hair, eyes, heart and bone. Let us study fat soluble vitamins one by one.