Introduction about Vitamin B2, Chemistry of Riboflavin, Biochemical Functions of Riboflavin, Recommended Dietary Allowance of Vitamin B2, Dietary Sources of Riboflavin, Deficiency Symptoms of Vitamin B2, Synthesis of FMN, FAD from Riboflavin pathway, Coenzymes of Riboflavin.

3. Riboflavin (Vitamin B2)
• Riboflavin which has also known as Vitamin B2, Vitamin G and “
the yellow enzyme” was recognized as a vitamin in 1917.
• As early as 1897, a London chemist had observed in milk whey a
water-soluble pigment with peculiar yellow-green fluorescence.
• It was given the chemical group name flavin from the Latin word
for Yellow.
• Later because the vitamin was found also to contain a sugar
named ribose, the name riboflavin was adopted.

5. Riboflavin (Vitamin B2) - Chemistry
• Riboflavin through its coenzymes takes part in
a variety of cellular oxidation-reduction
reactions.
• Riboflavin contains 6,7-dimethyl
isoalloxazine ( a hetrocyclic 3 ring structure)
attached to D-ribitol by a nitrogen atom.

7. Riboflavin (Vitamin B2) - Chemistry

9. Riboflavin (Vitamin B2) - Chemistry
• Coenzymes of Riboflavin
• Flavin mononucleotide (FMN) and Flavin
Adenine dinucleotide (FAD) are the two
coenzyme forms of riboflavin. The ribitol (5
carbon) is linked to a phosphate in FMN. FAD
is formed from FMN by the transfer of an AMP
moiety from ATP.

12. Riboflavin (Vitamin B2) - Biochemical
functions
I. The flavin coenzymes (mostly FAD and to a lesser extent
FMN) participate in many redox reactions responsible for
energy production.
• The functional unit of both the coenzymes is isoalloxazine
ring which serves as an acceptor of two hydrogen atoms
(with electrons).
• FMN or FAD undergo identical reversible reactions
accepting two hydrogen atoms forming FMNH2 or
FADH2.

13. Riboflavin (Vitamin B2) – Biochemical
Functions
II. Enzymes that use flavin coenzymes (FMN or FAD) are
called flavoproteins.
• Many flavoproteins contain metal atoms (iron, molybdenum
etc.) which are known as metalloflavoproteins.
• The coenzymes, FAD and FMN are associated with several
enzymes involved in carbohydrate, lipid, protein, and purine
metabolisms, besides the electron transport chain.

16. Riboflavin (Vitamin B2) - Recommended
dietary allowance (RDA)
• The daily requirement of riboflavin for an
adult is 1.2-1.7mg.
• Higher intakes (by 0.2-0.5 mg/day) are
advised for pregnant and lactating women.

18. Riboflavin (Vitamin B2) – Dietary
Sources
• Milk and milk products, meat, eggs, liver,
kidney, are rich sources.
• Cereals, fruits, Vegetables and fish are
moderate sources.

20. Riboflavin (Vitamin B2) - Deficiency
Symptoms
• Riboflavin deficiency symptoms include:
• Cheilosis (fissure at the corner of the mouth),
• Glossitis (tongue smooth and purplish) and
• Dermatitis.
• Assay of the enzyme Glutathione Reductase in
erythrocytes will be useful in assessing the
riboflavin deficiency.