Vitamin B2 is a water soluble vitamin.The main circulating forms of vitamin B2 are riboflavin and its two cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These two forms are detectable in both plasma and blood cells, however, the predominant form is FAD found in red blood cells. FMN and FAD act as cofactors in oxidation-reduction reactions and in the respiratory chain and are thus involved in energy production (eg. cytochrome, glutathione reductase, glutathione peroxidase, xanthine oxidase and methylene tetrahydrofolatereductase). Flavins also have antioxidant functions, removing free radicals to reduce oxidative damage to lipids and other macromolecules. As an antioxidant, FAD is a coenzyme to glutathione reductase. Flavin coenzymes are also involved in the metabolism of four other vitamins – vitamin B12, folic acid, vitamin B6 (for conversion to the coenzyme pyridoxal 5 phosphate) and niacin (conversion of tryptophan to niacin)
Vitamin B2 is chemically classified as a flavin from the Latin word flavus, meaning “yellow.” Flavins are so-named because they quickly turn yellow in the presence of oxygen. Vitamin B2 was originally known as ovoflavin since it was a flavin derived from eggs. It was later renamed “riboflavin” since it’s derived from the sugar ribose.
Yeast extract is one of the richest dietary sources of riboflavin. Additional foods that are high in riboflavin include dairy products, leafy vegetables and organ meats. Unrefined cereal grains are also common dietary sources of riboflavin. However, the refining process removes the majority of vitamin B2 from cereal grains since this nutrient is concentrated in the outer layers of the grain. Many cereal manufacturers therefore add vitamin B2 and other nutrients to their products.
Many liquids also need to be supplemented with vitamin B2, including sauces, beverages and milk products. However, this is difficult to accomplish with pure riboflavin, which is only slightly soluble in water. Manufacturers often use riboflavin-5′-phosphate to add vitamin B2 to food and health supplements, since it is significantly more water soluble than riboflavin.
Riboflavin-5′-phosphate, also known as flavin mononucleotide (FMN), is made by using the enzyme riboflavin kinase to catalyze a reaction with riboflavin. It’s a strong oxidizing agent that plays a role in many reactions involving the transfer of multiple electrons. Riboflavin-5′-phosphate is also the principal form of riboflavin in the body, although it requires more energy to produce.