CHAPTER 6: Chemistry and Biochemistry of Riboflavin and Related Compounds

Riboflavin is the biologically active component of the prosthetic group of many enzymes and proteins collectively known as flavoproteins. Riboflavin is one of the most stable vitamins. The typical mechanism for riboflavin degradation is photochemical. This vitamin is widely distributed and the main contributors for its intake in Western countries are meat and dairy. Flavins play key metabolic roles in biological oxidation-reduction reactions involving carbohydrates, lipids, amino acids and other water-soluble vitamins, and in energy production via the respiratory chain. During digestion, flavins are released and available for absorption, which occurs in the intestine by a specific Na⁺-independent carrier. Transport in plasma is mediated through associations with albumin and immunoglobulins. Interconversion of riboflavin to its active forms occurs by the actions of specific intestinal enzymes. When riboflavin intake surpasses the body requirements, the excess is excreted in urine as free riboflavin and other metabolites. Riboflavin inadequacy is rare and observed only in populations whose diet is lacking dairy products and meat, or in patients with absorptive disorders.