Biotin is a heterocyclic, sulphur containing monocarboxylic acid (Fig. 8.11). Biotin is sparingly soluble in cold water and is freely soluble in hot water.
Biotin is required as the co-factor for a small number of carboxylation reactions, it acts as the carrier for carbon dioxide.
· It helps to maintain the skin and the nervous systems in good condition.
· It assists in the deamination of amino acids like aspartic acid, serine and threonine.
· It helps in the synthesis of purine.
· For the conversion of ornithine to citrulline in the synthesis of urea, biotin is required.
Biotin occurs widely both in foods of vegetable and animal origin. Wheat germ, liver, peanut, and rice polishings are rich sources. Whole cereals, legumes, mutton and egg are good sources.
Since, intestinal bacteria and diets supply biotin in adequate amounts the deficiency of this vitamin in human being is rare.
Infants - 10- 15 μg/day
Children - 20-40 μg/day
Adults - 50-60 μg/day
Biotin is readily absorbed from the small intestine through the portal vein into the general circulation. Excess of the requirements is not stored in the body but is mostly excreted in the urine.
There is a protein in egg white called avidin which is responsible for producing egg white injury. Avidin binds with biotin tightly in the intestinal tract and prevents absorption of biotin from intestines. Avidin is denatured by cooking and then loses its ability to bind with biotin. The amount of avidin in uncooked egg white is relatively small, and problems of biotin deficiency have only occurred in people eating abnormally large amounts of raw eggs for many years.
Deficiency of biotin is rare in human beings.