chemistry and metabolism of vitamins

1. Chemistry and metabolism of
vitamins
By
E.Nagendram
Dept. of Biochemistry
Osmania University

2. Discovery of vitamins
A vitamin is an organic molecule (or a set of molecules
closely related chemically, i.e. vitamers) that is an essential
micronutrient which an organism needs in small quantities for
the proper functioning of its metabolism. Essential nutrients
cannot be synthesized in the organism, either at all or not in
sufficient quantities, and therefore must be obtained through
the diet. Vitamin C can be synthesized by some species but
not by others; it is not a vitamin in the first instance but is in
the second. The term vitamin does not include the three other
groups of essential nutrients: minerals, essential fatty acids,
and essential amino acids.

3. Most vitamins are not single molecules, but groups of related
molecules called vitamers. For example, there are eight
vitamers of vitamin E: four tocopherols and four tocotrienols.
Some sources list fourteen vitamins, by including choline, but
major health organizations list thirteen: vitamin A (as all-trans-
retinol, all-trans-retinyl-esters, as well as all-trans-beta-
carotene and other provitamin A carotenoids), vitamin B1
(thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin
B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B7
(biotin), vitamin B9 (folic acid or folate), vitamin B12
(cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols),
vitamin E (tocopherols and tocotrienols), and vitamin K
(phylloquinone and menaquinones).

4. History of vitamins
History of Vitamins Disease related to deficiency and foods that help were
recognized long before the vitamin was discovered Vitamins became valued for
promoting public health 1940s U.S. government mandated specific vitamins be
added to grains and milk to improve health.
Dr.Funk introduced the term ‘vitamine’ for these organic compounds. The
vitamin, which funk extracted contained an amine and that is found to be
essential for ‘vital’ activities. Hence he coined the name vitamine.
But later it was found that amine was not present in all the vitamins discovered.
Hence ‘e’ was deleted and the term vitamin was used. Scientists are now
focusing on prevention of disease with vitamin research .

5. Classification of vitamins
•Naming Vitamins Each new vitamin is temporarily
named when discovered. The naming of vitamins
follows the letters of the alphabet, starting with A; we
are up to the letter K • A, B, C, D, E, and K - B has
many subscripts • F, G, and H were dropped.
• Classification of Vitamins :Classification is based
on solubility
• Eight water-soluble: B vitamin complex and vitamin
C • Four fat-soluble: vitamins A, D, E, and K
Solubility influences a vitamin’s • Digestion •
Absorption • Transportation • Storage • Excretion.

6. Classification of vitamins

7. Water soluble vitamins

8. Classification of vitamins
• WATER SOLUBLE vitamins: Dissolve in water • Readily excreted by
kidney • Function as a coenzyme & in energy metabolism .
• Vitamin C, thiamine and riboflavin are especially susceptible to heat
and alkalinity • Hydrophilic compounds and water leach them from
vegetables
• Marginal deficiency more common FAT SOLUBLE .
Adsorbed with dietary fat in micelles
• Excreted much more slowly
• Stored in adipose tissue & liver so pose a greater risk of toxicity
when consumed in excess
• Chylomicrons containing fat-soluble vitamins are transported via the
lymph to the bloodstream and eventually to the liver.

9. Structures of water soluble
vitamins