riboflavin

Question 1

Structure of riboflavin

Answer 1

Riboflavin is a yellow compound consisting of a isoalloxazine ring with a ribitol
(sugar alcohol) side chain.

Question 2

Active form of riboflavin

Answer 2

The active or coenzyme forms of the riboflavin are:
* Flavin mononucleotide (FMN), and
* Flavin adenine dinucleotide (FAD).

Question 3

Sources of riboflavin

Answer 3

• The main dietary sources of riboflavin are yeast,
  germinating seeds, green leafy vegetables milk and
  milk products, eggs, liver and meat.
• Cereals are a poor source.

Question 4

Functions of riboflavin

Answer 4

Riboflavin is a precursor of coenzymes FMN and
FAD, which are required by several oxidationreduction reactions in metabolism. FMN and FAD
serve as coenzymes for oxidoreductase enzymes
involved in carbohydrate, protein, lipid, nucleic acid
metabolism and electron transport chain.
Xanthine oxidase - purine degradation
succinate dehydrogenase - citric acid cycle
Acyl CoA dehydrogenase - fatty acid oxidation
* It is needed for maintenance of mucosal epithelial
and the ocular tissues.
* They are also involved in protection against peroxidation in metabolism of xenobiotics.

Question 5

Nutritional Requirements

Answer 5

• The RDA for vitamin B2 is 1.3 to 1.7 mg for adults.
• It is related to protein use and increases during
  growth, pregnancy, lactation and wound healing.

Question 6

Deficiency Manifestations

Answer 6

• Riboflavin deficiency is quite rare as it has a wide
  distribution in food stuffs. It is usually seen along with
  deficiencies of other vitamins of B-complex group. It
  is most commonly seen in chronic alcoholics.
• The characteristic symptoms of riboflavin deficiency
  are:
  – Cheilosis: Fissures at the angles of the mouth,
  – Glossitis: Inflammation of the tongue that
  becomes swollen and magenta colored
  – Dermatitis: Rough and scaly skin
  – Vascularization (the development of blood
  vessels) of cornea, etc.

Question 7

Riboflavin Assay

Answer 7

A commonly used method for assessment of riboflavin status uses the determination of FAD dependent glutathione reductase activity in freshly lyzed erythrocytes.