• Active forms: flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD)
  • Active forms of riboFlavin are FMN and FAD.
• Sources: meat, fish, eggs, milk, green vegetables, yeast

Functions

FAD and FMN are cofactors for enzymes that are involved in redox reactions (chemical reactions in which electrons are transferred from one substance to another), including:

• Succinate dehydrogenase (TCA cycle)
• FAD is part of glutathione reductase (GR) in erythrocytes: NADPH binds to GR → reduction of FAD to FADH- → FADH- breaks disulfide bond in GSSG → GSR can be reduced

Vitamin B2 deficiency

• Causes
  • Malnutrition
  • Restricted diet (e.g., vegan, lactose-free)
  • ↑ Demand: pregnancy, lactation
• Clinical features
  • Corneal vascularization
    • In riboflavin deficiency, the cornea may experience asphyxia (oxygen deprivation). The body responds by growing new blood vessels to deliver oxygen.
  • Cheilitis, glossitis, stomatitis, pharyngitis
    • Mucosal epithelial cells are rapidly renewing cells, easily affected.
  • Normocytic normochromic anemia
  • Seborrheic dermatitis
• Diagnosis
  • Erythrocyte glutathione reductase assay: identifies subtle deficiencies