Abstract

Riboflavin (vitamin B₂) has the chemical name 7,8-dimethyl-10-D-ribitylisoalloxazine, C₁₇H₂₀N₄O₆, mol wt 376.37. Riboflavin generally fulfills its metabolic function in the form of flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and other covalently bound flavin derivatives, which serve as the prosthetic groups (coenzymes). They combine with specific proteins (apoenzymes) to form flavoenzymes, in a series of oxidation–reduction catalysts widely distributed in nature.

As a coenzyme component in tissue oxidation–reduction and respiration, riboflavin is distributed in some degree in virtually all naturally occurring foods. Liver, heart, kidney, milk, eggs, lean meats, and fresh leafy vegetables are particularly good sources of riboflavin.

In 1935, Karrer and Kuhn independently proved that riboflavin was 7,8-dimethyl-10-D-ribitylisoalloxazine by total syntheses. For therapeutic use, riboflavin is produced by chemical synthesis, which consists of the condensation of 4,5-dimethyl-2-p-nitrophenylazo-1-D-ribitylaminobenzene with barbituric acid in an acidic medium, whereas the concentrates for poultry and livestock feeds are manufactured by fermentation using microorganisms such as Ashbya gossypii and Eremothecium ashbyii.

Riboflavin is essential for mammalian cells. A lack of it in the human diet causes well-defined syndromes, such as sore throat, hyperemia and edema of the pharyngeal and oral mucous membranes, cheilosis, angular stomatitis, and glossitis. A healthy adult requires ca 1.5–1.8 mg of riboflavin daily.

Derivatives include FMN, FAD, covalently bound flavins, 6-hydroxyriboflavin, reseoflavin, and 5-deazariboflavin.