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 also readily absorbed from the upper gastrointestinal tract; however, its absorption involves an active transport mechanism, and the extent of gastrointestinal absorption is limited by the contact time between the drug and the site of absorption—a specific mucosal segment. Riboflavin 5-phosphate is rapidly and almost completely dephosphorylated in the gastrointestinal lumen before absorption. Co-administration with food increases the gastrointestinal absorption of riboflavin, while absorption is reduced in patients with hepatitis, cirrhosis, biliary obstruction, or those taking probenecid. Riboflavin is primarily absorbed in the small intestine via a rapid, saturable transport system. A small amount of riboflavin is absorbed in the large intestine. The absorption rate of riboflavin is directly proportional to the intake amount, increasing when ingested with other foods and in the presence of bile salts. At low intake levels, riboflavin is primarily absorbed via active or facilitated diffusion systems. At high intake levels, riboflavin can be absorbed via passive diffusion. In plasma, most riboflavin is transported by binding with other proteins, primarily immunoglobulins. Pregnancy increases the levels of carrier proteins available for riboflavin, thereby enhancing its absorption on the maternal placental surface. In the stomach, gastric acid releases most of the coenzymatic forms of riboflavin (flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN)) from the proteins. The non-covalently bound coenzymes are then hydrolyzed into riboflavin in the upper digestive tract by non-specific pyrophosphatases and phosphatases. Primary absorption of riboflavin occurs in the proximal small intestine via a rapid, saturable transport system. The absorption rate is proportional to the intake amount, increasing when riboflavin is ingested with other foods and in the presence of bile acids. A small amount of riboflavin circulates through the enterohepatic circulation system. At low intake levels, riboflavin absorption occurs primarily through active transport or facilitated diffusion systems. For more complete data on the absorption, distribution, and excretion of riboflavin (16 in total), please visit the HSDB records page.

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Metabolism/Metabolites
Liver metabolism.
Free riboflavin is converted to flavin mononucleotides in the intestinal mucosa, which are then converted to flavin adenine dinucleotides in the liver.
Riboflavin metabolism is a tightly regulated process, dependent on individual riboflavin levels. Riboflavin is converted to coenzymes in the cytoplasm of most tissues, but primarily occurs in the small intestine, liver, heart, and kidneys. Riboflavin metabolism begins with ATP-dependent phosphorylation of the vitamin, producing flavin mononucleotides (FMNs). Flavin kinases are the catalysts for this conversion and are hormonally regulated. FMNs can bind to specific apoenzymes to form various flavoproteins; however, most FMNs are converted to flavin adenine dinucleotides (FADs) by FAD synthase. Therefore, FADs are the most abundant flavin coenzymes in the body's tissues. FAD production is controlled by a product inhibition mechanism; excess FADs inhibit further production.
The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose-5-phosphate as substrates. GTP is hydrolyzed and converted to 5-amino-6-ribosylamino-2,4(1H,3H)-pyrimidinidone via a series of deamination, side-chain reduction, and dephosphorylation reactions. 3,4-dihydroxy-2-butanone-4-phosphate, derived from ribulose-5-phosphate, condenses to 6,7-dimethyl-8-ribosylpterin. The final step in vitamin biosynthesis is the disproportionation of 6,7-dimethyl-8-ribosylpterin catalyzed by riboflavin synthase. This reaction mechanism is unique, involving the transfer of a four-carbon fragment between two identical substrate molecules. The second product, 5-amino-6-ribosylamino-2,4(1H,3H)-pyrimidinidone, can be recycled in the biosynthetic pathway via 6,7-dimethyl-8-ribosylpterin synthase. This article reviews the structure and reaction mechanisms of riboflavin synthase and related proteins up to 2007, citing 122 references.
Liver.
Half-life: 66-84 minutes

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Biological half-life
66-84 minutes
In healthy individuals, the biological half-life of a single oral or intramuscular injection of a large dose of riboflavin is approximately 66-84 minutes.

Toxicity Summary
Riboflavin binds to riboflavin hydrogenase, riboflavin kinase, and riboflavin synthase. Riboflavin is a precursor to flavin mononucleotide (FMN, riboflavin monophosphate) and flavin adenine dinucleotide (FAD). The antioxidant activity of riboflavin primarily derives from its role as a FAD precursor and its role as a cofactor in the formation of the antioxidant reduced glutathione. Reduced glutathione is a cofactor for various enzymes, including selenium-containing glutathione peroxidase. Glutathione peroxidase is an important antioxidant enzyme. Reduced glutathione is produced by the FAD-containing enzyme glutathione reductase. Protein Binding 60% Interactions Riboflavin interacts with other B vitamins, particularly niacin (which requires riboflavin for its conversion from tryptophan) and vitamin B6 (which also requires riboflavin for its conversion to a coenzyme form). These interactions are currently known not to affect the required riboflavin intake.
It has been reported that propylthiophene bromide can affect the rate and extent of riboflavin absorption. Previous administration of propylthiophene bromide may slow the rate of riboflavin absorption but increase the total amount absorbed, possibly due to prolonged residence time of riboflavin at the gastrointestinal absorption site.
Alcohol can impair the intestinal absorption of riboflavin.
Concomitant use with probenecid may reduce the gastrointestinal absorption of riboflavin; patients taking probenecid may need to increase their riboflavin dosage.
For more complete data on interactions of riboflavin (7 types), please visit the HSDB record page.

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Non-human toxicity values
Oral LD50 in rats > 10,000 mg/kg
Intraperitoneal LD50 in rats 560 mg/kg
Subcutaneous LD50 in rats 5000 mg/kg

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

Therapeutic Uses
Riboflavin is used for the prevention and treatment of riboflavin deficiency. Poor dietary habits should be corrected whenever possible, and many clinicians recommend multivitamin preparations containing riboflavin for patients with vitamin deficiencies, as poor diets often lead to multiple vitamin deficiencies. Riboflavin may help treat microcytic anemia in patients with familial metabolic disorders accompanied by splenomegaly and glutathione reductase deficiency. Although there are no adequately controlled trials confirming any therapeutic value of riboflavin, it has been used to treat acne, congenital methemoglobinemia, muscle spasms, and burning pain syndrome. Patients undergoing hemodialysis or peridialysis, as well as those with severe malabsorption, may require additional riboflavin supplementation. Women carrying multiple pregnancies or breastfeeding multiple infants may also require higher levels of riboflavin. Individuals with high levels of physical activity may also need to increase their riboflavin intake. For more complete data on the therapeutic uses of riboflavin (11 in total), please visit the HSDB records page.

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Drug Warning
Taking riboflavin may cause urine to be more yellow than normal, especially at high doses. This is normal and nothing to worry about. However, riboflavin usually does not cause any side effects.
In 49 patients who received 400 mg of riboflavin daily (with food) for at least 3 months, no short-term side effects were observed. One patient who was taking riboflavin and aspirin simultaneously withdrew from the study due to stomach upset.This isolated finding may be unusual, as no other patients reported any side effects.Maternal medications generally compatible with breastfeeding: Riboflavin: Signs or symptoms reported by the infant or effects on lactation: None. (Excerpt from Table 6)Infants receiving treatment for hyperbilirubinemia may also be sensitive to excessive riboflavin.For more complete data on drug warnings for riboflavin (of 6), please visit the HSDB records page. Pharmacodynamics Riboflavin, or vitamin B2, is an easily absorbed, water-soluble micronutrient that plays a crucial role in maintaining human health. Like other B vitamins, it supports energy production by helping metabolize fats, carbohydrates, and proteins. Vitamin B2 is also essential for red blood cell formation and respiration, antibody production, and the regulation of human growth and reproduction. It is vital for healthy skin, nails, hair growth, and overall health, including regulating thyroid activity. Riboflavin also helps prevent or treat a variety of eye diseases, 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.)