Chemical and physical properties of biotin

Chemical and physical properties of biotin (vitamin B7, vitamin H)

1. Chemical and physical
properties of biotin
Domina Petric, MD

2. Essential features of the chemical
structure:
Conjoined ureido and
tetrahydrothiophene nuclei
Ureido 3′ nitrogen is sterically
hindered, preventing substitution
Ureido 1′ nitrogen is poorly
nucleophilic
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
2

3. Biotin nomenclature
•Biotinis the trivial
designation of the compound
cis-hexahydro-2-oxo-1H-
thieno[3,4-d]imidazole-4-
pentanoic acid, also known
as vitamin H, vitamin B7 and
coenzyme R.
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
3

4. Chemical and physical properties
Biotin is a white crystalline
substance that, in dry form,is
fairly stable to air, heat and light.
In solution,it is sensitive to
degradation under strongly
acidicor basic conditions.
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
4

5. Chemical and physical properties
•Its structure consists of a planar
ureidonucleusand a folded
tetrahydrothiophene(thiophane)
nucleus, which results in a boat
configurationwith a plane of
symmetry passing through the S-1,
C-2′,and O positionsin such a way
as to elevate the sulfuratom above
the plane of the four carbons.
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
5

6. Chemical and physical properties
The moleculehas three
asymmetric centers.
Of the eightpossible
stereoisomers, only the (+)-
isomer (calledd-biotin) has
biological activity.
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
6

7. Chemical and physical properties
•Biotin is covalentlybound to its
enzymes by an amide bond to the
ε-aminogroupof a lysine residue
and C-2 of the thiophanenucleus.
•This bond is flexible, allowing the
coenzymeto move between the
active centers of some enzymes.
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
7

8. Chemical and physical properties
•The biotin molecule is activated by
polarization of theO and N-1′ atoms of
the ureidonucleus.
•This leads toincreased nucleophilicityat
N-1′, which promotes theformation of a
covalent bond between the electrophilic
carbonyl phosphate formed from
bicarbonate and ATP,and allows biotin to
serve as a transport agent for CO
2.
April 18, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
8

9. Literature
•Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
April 18, 2018 9