Pharmacology: PHR 324
Chapter 6: Vitamins
Fat soluble vitamins
Vitamin A (Retinol)
Vitamin D (Cholecalciferol)
Vitamin E (Tocopherols)
Vitamin K (Phylloquinone)
Water soluble vitamins
Vitamin B complex
1. Vitamin B1 (Thiamine) 2. Vitamin B2 (Riboflavin) 3. Vitamin B3 (Niacin)
4. Vitamin B5 (Pantothenic acid) 5. Vitamin B6 (Pyridoxine)
6. Vitamin B7 (Biotin) 7. Vitamin B9 (Folates)
8. Vitamin B12 (Cyanocobalamine)
Vitamin C (Ascorbic acid)
Types of vitamins
Provitamin
A provitamin is a substance that may be converted within the body to a vitamin.
For example,
"Provitamin B5" is a name for panthenol, which may be converted in the body to vitamin B5 (pantothenic acid).
“Provitamin A" is a name for β-carotene, the body uses an enzyme to convert β-carotene to retinol.
Provitamin D2 is ergosterol, and provitamin D3 is 7-dehydrocholesterol.
Menadione is a synthetic provitamin of vitamin K.
Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids (most notably beta-carotene).
Vitamin A has multiple functions:
o it is important for growth and development
o for the maintenance of the immune system and good vision o used to treat and prevent Xerophthalmia.
In the eye, vitamin A in the form of retinal form rhodopsin with the combination of a
protein opsin. Rhodopsin is a light-absorbing molecule necessary for both low-light vision and colour vision.
Vitamin A
High doses may result in an enlarged liver, dry skin.
High doses during pregnancy may result in harm to the baby.
Vitamin D
We take vitamin D in two forms: Cholecalciferol (D3) and Ergocalciferol (D2).
Cholecalciferol and ergocalciferol can be ingested from the diet and from supplements.
Vitamin D from the diet, or from skin synthesis, is biologically inactive. A protein enzyme must hydroxylate it to convert it to the active form. This is done in the liver and in the kidneys.
In the liver as Calcidiol and in the Kidney as Calcitriol.
Calcitriol is the biologically active vitamin D.
Metabolism of Vitamin D
Cholecalciferol is converted in the liver to calcifediol (25-hydroxycholecalciferol); ergocalciferol is converted to 25- hydroxyergocalciferol. These two vitamin D are measured in serum to determine a person's vitamin D status.
Calcifediol is further hydroxylated by the kidneys to form calcitriol (also known as 1,25-dihydroxycholecalciferol), the biologically active form of vitamin D. Calcitriol circulates as a hormone in the blood, having a major role regulating the concentration of Ca+2 and PO4.
Vitamin E exists in eight different forms, four tocopherols and four tocotrienols.
Both the tocopherols and tocotrienols occur in α (alpha), β (beta), γ (gamma) and δ (delta) forms, determined by the number and position of methyl groups on the
chromanol ring.
Vitamin E
The tocopherols have saturated side chains, whereas tocotrienols have unsaturated side chains with three double bonds
Vitamin E deficiency causes neurological problems due to poor nerve conduction.
These include neuromuscular problems such as spinocerebellar ataxia and myopathies.
Vitamin K includes two natural vitamers: vitamin K1 (phylloquinone) and K2 (menaquinone)
Vitamin K
Vitamin K1 is made by plants, and is found in highest amounts in green leafy vegetables. It performs the classic functions of vitamin K.
Animals may convert vitamin K1 to vitamin K2 which is the main storage form of vitamin K in animals.
Vitamin K is required for complete synthesis of certain proteins that are prerequisites for blood coagulation.
B complex vitamin usually delivers eight of the B vitamins:
B1 (thiamine)
B2 (riboflavin)
B3 (niacin)
B5 (pantothenic acid)
B6 (pyridoxine)
B7 (biotin)
B9 (folic acid)
B12 (cobalamin).
Found naturally in meat, leafy greens, dairy, beans, peas, and whole or fortified grains.
Vitamin B complex
Functions:
B1 (Thiamine): Vitamin B1 helps the body make new cells.
B2 (Riboflavin): This B vitamin is important for red blood cell production and fighting free radicals.
B3 (Niacin): Helps regulate the nervous and digestive systems and aids in the conversion of food into energy.
B5 (Pantothenic acid): Breaks down fats and carbohydrates for energy and is responsible for the production of hormones.
Vitamin B complex
Functions:
B6 (Pyridoxine): Helps the body turn food into energy. Vitamin B6 also helps the body fight infection.
B7 (Biotin): Involved in the production of hormones.
B9 (Folic acid): This B vitamin helps cells make and maintain DNA and
promotes the growth of red blood cells. It also helps to reduce the risk of birth defects.
B12 (Cobalamin): Vitamin B12 helps regulate the nervous system and plays a role in red blood cell formation.
Vitamin B complex
VIT B12 FOLIC ACID
Vitamin B complex in
neuropathy
High blood levels of homocysteine signal a breakdown in this vital process, resulting in far-reaching
biochemical and life consequences.
Significant deficiencies in the homocysteine re- methylation cofactors cobalamin (B12) and folate, as well as the trans-sulfuration
cofactor vitamin B6, are commonly seen in the elderly population, with a resultant increase in
homocysteine
A significant correlation has been found between risk of Alzheimer's disease & cardiovascular disease with high plasma levels of homocysteine, as well as low levels of folic acid, and vitamins B6 and B12.
