Flavin mononucleotide

Flavin mononucleotide (FMN), or riboflavin-5′-phosphate, is a biomolecule produced from riboflavin (vitamin B₂) by the enzyme riboflavin kinase and functions as the prosthetic group of various oxidoreductases, including NADH dehydrogenase, as well as a cofactor in biological blue-light photo receptors.^[2] During the catalytic cycle, various oxidoreductases induce reversible interconversions between the oxidized (FMN), semiquinone (FMNH^•), and reduced (FMNH₂) forms of the isoalloxazine core. FMN is a stronger oxidizing agent than NAD and is particularly useful because it can take part in both one- and two-electron transfers. In its role as blue-light photo receptor, (oxidized) FMN stands out from the 'conventional' photo receptors as the signaling state and not an E/Z isomerization.

Flavin mononucleotide

Names
IUPAC name 1-Deoxy-1-(7,8-dimethyl-2,4-dioxo-3,4-dihydrobenzo[g]pteridin-10(2H)-yl)-D-ribitol 5-(dihydrogen phosphate)
Systematic IUPAC name (2R,3S,4S)-5-(7,8-Dimethyl-2,4-dioxo-3,4-dihydrobenzo[g]pteridin-10(2H)-yl)-2,3,4-trihydroxypentyl dihydrogen phosphate
Other names FMN Epioxa Epioxa HD
Identifiers
CAS Number	146-17-8 130-40-5 (sodium salt)
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17621
ChEMBL	ChEMBL1201794
ChemSpider	559060
ECHA InfoCard	100.005.150
E number	E101a (colours)
IUPHAR/BPS	5185
MeSH	Flavin+mononucleotide
PubChem CID	643976
UNII	7N464URE7E Y
CompTox Dashboard (EPA)	DTXSID8023559
InChI InChI=1S/C17H21N4O9P/c1-7-3-9-10(4-8(7)2)21(15-13(18-9)16(25)20-17(26)19-15)5-11(22)14(24)12(23)6-30-31(27,28)29/h3-4,11-12,14,22-24H,5-6H2,1-2H3,(H,20,25,26)(H2,27,28,29)/t11-,12+,14-/m0/s1 Key: FVTCRASFADXXNN-SCRDCRAPSA-N
SMILES Cc1cc2c(cc1C)n(c-3nc(=O)[nH]c(=O)c3n2)C[C@@H]([C@@H]([C@@H](COP(=O)(O)O)O)O)O
Properties
Chemical formula	C17H21N4O9P
Molar mass	456.344 g/mol
Melting point	195 °C
Pharmacology
ATC code	S01XA26 (WHO)
Routes of administration	Ophthalmic
Legal status	US: ℞-only[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

It is the principal form in which riboflavin is found in cells and tissues. It requires more energy to produce, but is more soluble than riboflavin. In cells, FMN occurs freely circulating but also in several covalently bound forms.^[3] Covalently or non-covalently bound FMN is a cofactor of many enzymes playing an important pathophysiological role in cellular metabolism. For example dissociation of flavin mononucleotide from mitochondrial complex I has been shown to occur during ischemia/reperfusion brain injury during stroke.^[4][5]

Food additive

Flavin mononucleotide is also used as an orange-red food colour additive, designated in Europe as E number E101a.^[6]

E106, a very closely related food dye, is riboflavin-5′-phosphate sodium salt, which consists mainly of the monosodium salt of the 5′-monophosphate ester of riboflavin. It is rapidly turned to free riboflavin after ingestion. It is found in many foods for babies and young children as well as jams, milk products, and sweets and sugar products.^[7]

Medical uses

Flavin mononucleotide

Clinical data
AHFS/Drugs.com	Epioxa
License data	US DailyMed: Riboflavin 5
Identifiers
DrugBank	DB03247
E number	E101a (colours)
CompTox Dashboard (EPA)	DTXSID8023559
ECHA InfoCard	100.005.150

Riboflavin 5'-phosphate (Epioxa) and riboflavin 5’-phosphate sodium (Epioxa HD) and are photoenhancers that are indicated for use in epithelium-on corneal collagen cross-linking for the treatment of keratoconus in people aged thirteen years of age and older, in conjunction with the O2n System and the Boost Goggles.^[1]

Flavin mononucleotide, or riboflavin-5'-phosphate, is a biomolecule produced from riboflavin by the enzyme riboflavin kinase and functions as prosthetic group of various oxidoreductases including NADH dehydrogenase as well as cofactor in biological blue-light photo receptors.^[8] Riboflavin 5'-phosphate sodium is a mixture of the sodium salts of riboflavin, riboflavin monophosphates, and riboflavin diphosphates.^[1]

Epioxa and Epioxa HD were approved for medical use in the United States in October 2025.^[9]

See also

• Flavin adenine dinucleotide