Vitamin B7 (Vitamin H or Biotin)

 Vitamin B₇ (Vitamin H or Biotin)

(Anti-Egg-White-Injury Factor)

Introduction

In 1916, Bateman observed that a diet containing high percentage of egg-white was toxic to animals. In 1941, avidin the protein isolated from egg-white was found to prevent absorption of biotin Allison and others (1933) isolated another growth factor and named it coenzyme R which was later found to be identical to biotin. Its structure was identified in 1942 and synthesized in 1943.

Chemistry

Biotin is a heterocyclic, s-containing monocarboxylic acid, a valeric acid derivative containing two five-sided rings (thieno and imidazole) fused together. In naturally-occurring biotin, biocytin has been identified as a lysine biotin conjugate.

Properties

·        soluble in water and alcohol

·        heat-stable 

·        resistant to acids and alkalis

·        contains sulphur

Distribution

Animal sources

·        Egg yolk

·        kidney

·        liver

Raw egg-white contains avidin which is antibiotin in nature.

Plant sources

·        Cauliflower

·        peas

Functions

(1) Biotin acts as coenzyme for carboxylase, so as to help in carboxylation reactions like in urea formation and bio synthesis of pyrimidines and fatty acids.

(2) It also helps in deamination of threonine, serine and aspartic acid.

 (3) An important function of biotin is in the coenzyme activity related to carbamyl phosphate synthesis and reaction related to it.

Deficiency signs

No clear deficiency signs found.

Daily requirement

In human beings it is 150-300 mcg per day on the average. Average daily diet contains sufficient amount.