Riboflavin (vitamin B2) is the direct precursor of redox enzyme cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are essential for multiple cell physiology. The riboflavin biosynthetic pathway is regarded as a rich resource for therapeutic targets for broad spectrum antibiotics. Such demonstrates the promise of riboflavin biosynthesis and regulatory mechanisms as potential therapeutic targets for novel antibiotic drug discovery.[1]

Absorption, Distribution and Excretion
Vitamin B2 is readily absorbed from the upper gastrointestinal tract.
Riboflavin is readily absorbed from the upper GI tract; however, absorption of the drug involves active transport mechanisms and the extent of GI absorption is limited by the duration of contact of the drug with the specialized segment of mucosa where absorption occurs. Riboflavin 5-phosphate is rapidly and almost completely dephosphorylated in the GI lumen before absorption occurs. The extent of GI absorption of riboflavin is increased when the drug is administered with food and is decreased in patients with hepatitis, cirrhosis, biliary obstruction, or in those receiving probenecid.
Primary absorption of riboflavin occurs in the small intestine via a rapid, saturable transport system. A small amount is absorbed in the large intestine. The rate of absorption is proportional to intake, and it increases when riboflavin is ingested along with other foods and in the presence of bile salts. At low intake levels, most absorption of riboflavin occurs via an active or facilitated transport system. At higher levels of intake, riboflavin can be absorbed by passive diffusion.
In the plasma, a large portion of riboflavin associates with other proteins, mainly immunoglobulins, for transport. Pregnancy increases the level of carrier proteins available for riboflavin, which results in a higher rate of riboflavin uptake at the maternal surface of the placenta.
In the stomach, gastric acidification releases most of the coenzyme forms of riboflavin (flavin-adenine dinucleotide (FAD) and flavin mononucleotide (FMN)) from the protein. The noncovalently bound coenzymes are then hydrolyzed to riboflavin by nonspecific pyrophosphatases and phosphatases in the upper gut. Primary absorption of riboflavin occurs in the proximal small intestine via a rapid, saturable transport system. The rate of absorption is proportional to intake, and it increases when riboflavin is ingested along with other foods and in the presence of bile salts. A small amount of riboflavin circulates via the enterohepatic system. At low intake levels most absorption of riboflavin is via an active or facilitated transport system.
For more Absorption, Distribution and Excretion (Complete) data for Riboflavin (16 total), please visit the HSDB record page.

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Metabolism / Metabolites
Hepatic.
Free riboflavin is converted in the intestinal mucosa into flavin mononucleotide which is transformed into flavin adenine dinucleotide in the liver.
The metabolism of riboflavin is a tightly controlled process that depends on the riboflavin status of the individual. Riboflavin is converted to coenzymes within the cellular cytoplasm of most tissues but mainly in the small intestine, liver, heart, and kidney. The metabolism of riboflavin begins with the adenosine triphosphate (ATP)-dependent phosphorylation of the vitamin to flavin mononucleotide (FMN). Flavokinase, the catalyst for this conversion, is under hormonal control. FMN can then be complexed with specific apoenzymes to form a variety of flavoproteins; however, most is converted to flavin-adenine dinucleotide (FAD) by FAD synthetase. As a result, FAD is the predominant flavocoenzyme in body tissues. Production of FAD is controlled by product inhibition such that an excess of FAD inhibits its further production.
The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. GTP is hydrolytically opened, converted into 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation with 3,4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate leads to 6,7-dimethyl-8-ribityllumazine. The final step in the biosynthesis of the vitamin involves the dismutation of 6,7-dimethyl-8-ribityllumazine catalyzed by riboflavin synthase. The mechanistically unusual reaction involves the transfer of a four-carbon fragment between two identical substrate molecules. The second product, 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione, is recycled in the biosynthetic pathway by 6,7-dimethyl-8-ribityllumazine synthase. This article will review structures and reaction mechanisms of riboflavin synthases and related proteins up to 2007 and 122 references are cited.
Hepatic.
Half Life: 66-84 minutes

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Biological Half-Life
66-84 minutes
The biologic half-life of riboflavin is about 66-84 minutes following oral or IM administration of a single large dose in healthy individuals.

Toxicity Summary
Binds to riboflavin hydrogenase, riboflavin kinase, and riboflavin synthase. Riboflavin is the precursor of flavin mononucleotide (FMN, riboflavin monophosphate) and flavin adenine dinucleotide (FAD). The antioxidant activity of riboflavin is principally derived from its role as a precursor of FAD and the role of this cofactor in the production of the antioxidant reduced glutathione. Reduced glutathione is the cofactor of the selenium-containing glutathione peroxidases among other things. The glutathione peroxidases are major antioxidant enzymes. Reduced glutathione is generated by the FAD-containing enzyme glutathione reductase.

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Protein Binding
60%

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Interactions
Riboflavin interrelates with other B vitamins, notably niacin, which requires riboflavin for its formation from tryptophan, and vitamin B6, which also requires riboflavin for a conversion to a conenzyme form. These interrelationships are not known to affect the requirement for riboflavin.
The rate and extent of absorption of riboflavin are reportedly affected by propantheline bromide. Prior administration of propantheline bromide delayed the rate of absorption of riboflavin but increased the total amount absorbed, presumably by increasing the residence time of riboflavin at GI absorption sites.
Alcohol impairs intestinal absorption of riboflavin.
Concurrent use /with probenecid/ decreases gastrointestinal absorption of riboflavin; requirements for riboflavin may be increased in patients receiving probenecid.
For more Interactions (Complete) data for Riboflavin (7 total), please visit the HSDB record page.

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Non-Human Toxicity Values
LD50 Rat oral > 10,000 mg/kg
LD50 Rat ip 560 mg/kg
LD50 Rat sc 5000 mg/kg

Chem Biol Drug Des, 2010. 75(4): p. 339-47.

Therapeutic Uses
Riboflavin is used to prevent riboflavin deficiency and to treat ariboflavinosis. Whenever possible, poor dietary habits should be corrected, and many clinicians recommend administration of multivitamin preparations containing riboflavin in patients with vitamin deficiencies since poor dietary habits often result in concurrent deficiencies.
Riboflavin may be useful in treating microcytic anemia that occurs in patients with a familial metabolic disease associated with splenomegaly and glutathione reductase deficiency.
Although riboflavin has not been shown by well-controlled trials to have any therapeutic value, the drug also has been used for the management of acne, congenital methemoglobinemia, muscle cramps, and burning feet syndrome.
People undergoing hemodialysis or peritioneal dialysis and those with severe malabsorption are likely to require extra riboflavin. Women who are carrying more than one fetus or breastfeeding more than one infant are also likely to require more riboflavin. It is possible that individuals who are ordinarily extremely physically active may also have increased needs for riboflavin.
For more Therapeutic Uses (Complete) data for Riboflavin (11 total), please visit the HSDB record page.

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Drug Warnings
Riboflavin may cause urine to have a more yellow color than normal, especially if large doses are taken. This is to be expected and is no cause for alarm. Usually, however, riboflavin does not cause any side effects.
No short-term side effects /were observed/ in 49 patients treated with 400 mg/day of riboflavin taken with meals for at least 3 months. One patient receiving riboflavin and aspirin withdrew from the study because of gastric upset. This isolated finding may be an anomaly because no side effects were reported in other patients.
Maternal Medication usually Compatible with Breast-Feeding: Riboflavin: Reported Sign or Symptom in Infant or Effect on Lactation: None. /from Table 6/
Infants treated for hyperbilirubinemia may also be sensitive to excess riboflavin.
For more Drug Warnings (Complete) data for Riboflavin (6 total), please visit the HSDB record page.

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Pharmacodynamics
Riboflavin or vitamin B2 is an easily absorbed, water-soluble micronutrient with a key role in maintaining human health. Like the other B vitamins, it supports energy production by aiding in the metabolising of fats, carbohydrates, and proteins. Vitamin B2 is also required for red blood cell formation and respiration, antibody production, and for regulating human growth and reproduction. It is essential for healthy skin, nails, hair growth and general good health, including regulating thyroid activity. Riboflavin also helps in the prevention or treatment of many types of eye disorders, including some cases of cataracts.

C17H20N4O6

376.37

376.138

83-88-5

Riboflavin phosphate sodium;130-40-5;Riboflavin-13C4,15N2;1217461-14-7;Riboflavin-5-Phosphate-13C4,15N2-1;Riboflavin-13C5;Riboflavin-d3;Riboflavine phosphate;146-17-8

493570

Light yellow to orange solid powder

1.7±0.1 g/cm3

715.6±70.0 °C at 760 mmHg

290 °C (dec.)(lit.)

386.6±35.7 °C

0.0±2.4 mmHg at 25°C

1.733

-2.01

5

7

5

27

680

3

CC1=CC2=C(C=C1C)N(C3=NC(=O)NC(=O)C3=N2)C[C@@H]([C@@H]([C@@H](CO)O)O)O

AUNGANRZJHBGPY-SCRDCRAPSA-N

InChI=1S/C17H20N4O6/c1-7-3-9-10(4-8(7)2)21(5-11(23)14(25)12(24)6-22)15-13(18-9)16(26)20-17(27)19-15/h3-4,11-12,14,22-25H,5-6H2,1-2H3,(H,20,26,27)/t11-,12+,14-/m0/s1

7,8-dimethyl-10-[(2S,3S,4R)-2,3,4,5-tetrahydroxypentyl]benzo[g]pteridine-2,4-dione

E101; E-101; E 101; Vitamin G; Lactoflavin;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~17.86 mg/mL (~47.45 mM)
H2O : ~14.29 mg/mL (~37.97 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)