B vitamins

B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism. Though these vitamins share similar names, research shows that they are chemically distinct vitamins that often coexist in the same foods. In general, dietary supplements containing all eight are referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific name of each vitamin (e.g., B₁, B₂, B₃ etc.).

Each B vitamin is either a cofactor (generally a coenzyme) for key metabolic processes or is a precursor needed to make one.

List of B vitamins

Note: other substances once thought to be vitamins, were given numbers in the B-vitamin numbering scheme, but were subsequently discovered to be either not essential for life or manufactured by the body, thus not meeting the two essential qualifiers for a vitamin. That is why those numbers (4, 8, 10 ,11) no longer appear in the classification.

B vitamin molecular functions

B vitamin deficiency

Several named vitamin deficiency diseases may result from the lack of sufficient B vitamins. Deficiencies of other B vitamins result in symptoms that are not part of a named deficiency disease.

Riboflavin

Riboflavin (vitamin B₂) is part of the vitamin B group. It is the central component of the cofactors FAD and FMN and as such required for a variety of flavoprotein enzyme reactions including activation of other vitamins. It was formerly known as vitamin G.

As a chemical compound, riboflavin is a yellow-orange solid substance with poor solubility in water compared to other B vitamins. Visually, it imparts color to vitamin supplements (and bright yellow color to the urine of persons taking a lot of it).

The name "riboflavin" comes from "ribose" (the sugar whose reduced form, ribitol, forms part of its structure) and "flavin", the ring-moiety which imparts the yellow color to the oxidized molecule (from Latin flavus, "yellow"). The reduced form, which occurs in metabolism along with the oxidized form, is colorless.

Function

Vitamins are small chemical compounds that humans (and other animals) cannot synthesize, but instead are absorbed from plant and animal foods. Riboflavin functions as a coenzyme, meaning that it is required for enzymes (proteins) to perform normal physiological actions. Specifically, the active forms or riboflavin Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) function as cofactors for a variety of flavoproteine enzyme reactions:

Folic acid

Folic acid or folate is a B vitamin. It is also referred to as vitamin M,vitamin B₉,vitamin B_c (or folacin), pteroyl-L-glutamic acid, and pteroyl-L-glutamate.

Food supplement manufacturers often use the term folate for something different from "pure" folic acid: in chemistry, folate refers to the deprotonated ion, and folic acid to the neutral molecule—which both coexist in water. The International Union of Pure and Applied Chemistry and the International Union of Biochemistry and Molecular Biology state that folate and folic acid are the preferred synonyms for pteroylglutamate and pteroylglutamic acid, respectively.

Folate indicates a collection of "folates" that is not chemically well-characterized, including other members of the family of pteroylglutamates, or mixtures of them, having various levels of reduction of the pteridine ring, one-carbon substitutions and different numbers of glutamate residues.

Folic acid is synthetically produced, and used in fortified foods and supplements on the theory that it is converted into folate. However, folic acid is a synthetic oxidized form, not significantly found in fresh natural foods. To be used it must be converted to tetrahydrofolate (tetrahydrofolic acid) by dihydrofolate reductase (DHFR). Increasing evidence suggests that this process may be slow in humans.