Menadione is a natural

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the formula C₆H₄(CO)₂C₂H(CH₃). It is an analog of 1,4-naphthoquinone with a

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...

in the 2-position. It is sometimes called vitamin K₃. Use is allowed as a

nutritional supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources or that are synthetic in order ...

animal feed Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word ''feed'' more often refers to fodder. Animal feed is an important input to ...

because of its

vitamin K Vitamin K refers to structurally similar, fat-soluble vitamers found in foods and marketed as dietary supplements. The human body requires vitamin K for post-synthesis modification of certain proteins that are required for blood coagulation ...

activity.

Biochemistry

Menadione is converted to

vitamin K2 Vitamin K2 or menaquinone (MK) () is one of three types of vitamin K, the other two being vitamin K1 ( phylloquinone) and K3 ( menadione). K2 is both a tissue and bacterial product (derived from vitamin K1 in both cases) and is usually found in ...

(specifically, MK-4) by the

prenyltransferase Prenyltransferases (PTs) are a class of enzymes that transfer allylic prenyl groups to acceptor molecules. Prenyl transferases commonly refer to isoprenyl diphosphate syntheses (IPPSs). Prenyltransferases are a functional category and include seve ...

action of

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

UBIAD1 UbiA prenyltransferase domain-containing protein 1 (UBIAD1) also known as transitional epithelial response protein 1 (TERE1) is a protein that in humans is encoded by the ''UBIAD1'' gene. The enzyme is named for its canonical role in ubiquinone ...

. This reaction requires the hydroquinone (reduced) form of K3, menadiol, produced by an unidentified enzyme. Menadione is also a circulating form of vitamin K, produced in small amounts (1–5%) after intestinal absorption of K1 and K2. This circulation explains the uneven tissue distribution of MK-4, especially since menadione can penetrate the

blood–brain barrier The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of the central nervous system where ne ...

. The cleavage enzyme is yet to be identified.

Terminology

The compound is variously known as vitamin K₃ and

provitamin A provitamin is a substance that may be converted within the body to a vitamin. The term previtamin is a synonym. The term "provitamin" is used when it is desirable to label a substance with little or no vitamin activity, but which can be converted ...

K₃. Proponents of the latter name generally argue that the compound is not a real

vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...

due to its artificial status (prior to its identification as a circulating intermediate) and its lack of a 3-methyl side chain preventing it from exert all the functions of the K vitamins.

Uses

It is an intermediate in the chemical synthesis of vitamin K by first reduction to the

diol A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common industrial diol is e ...

menadiol, which is susceptible to coupling to the phytol. In the United States, menadione is used in various types of animal feed and is described as having a history of safe use for this purpose, being used in poultry feed prior to 1958. Despite the fact that it can serve as a precursor to various types of

, menadione is generally not used as a nutritional supplement in economically developed countries. Menadione for human use at pharmaceutical strength is available in some countries with large lower income populations, such as India. The typical daily dose is 10 mg oral or 2 mg parenteral. It is used in the treatment of hypoprothrombinemia outside of the United States. Low-dose menadione is used as an inexpensive micronutrient for livestock in many countries. Forms of menadione are also included in some pet foods in developed countries as a source of vitamin K. These doses have yielded no reported cases of toxicity from menadione in livestock or pets. Although handling may be hazardous, the

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

found in 2013 that it is an effective source of vitamin K in animal nutrition that does not pose a risk to the environment.

References

External links

* {{Antihemorrhagics 1,4-Naphthoquinones Vitamin K