Riboflavin

376.36

376.36

201-507-1

1454

758973

DTXSID8021777

Fine orange-yellow needles from 2N acetic acid, alcohol, water, or pyridine ... three different crystal forms|Orange to yellow crystals or needles

29362300

161.56000

-1.67520

Yellow to orange Powder

1.2112 (rough estimate)

278-279 °C (decomp)

9℃

-135 ° (C=0.5, JP Method)

0.07 g/L (20 ºC)

2-8°C

LD50 in rats (g/kg): >10 orally, 5.0 s.c., 0.56 i.p. (Unna, Greslin)

-135 º (c=5, 0.05 M NaOH)

Slight odor

Bitter

pKa = 10.2; pKb = 1.7

Visible or ultraviolet radiation of alkaline solutions causes the formation of lumiflavine ... whereas irradiation of acid or neutral solutions gives rise to the production of lumichrome ... togther with varying amounts of lumiflavine|Sensitive to alkalies; stable to mineral acids in the dark|In solution, riboflavin has an intense greenish-yellow flourescence|In alkaline solution it is readily soluble but quite unstable to heat and to light forming lumiflavin, a fluorescent degradation product. Riboflavin is nore stable to heat in acid solution, particularly from pH 1.0 to 6.5 but upon irradiation forms lumichrome. Riboflavin is readily adsorbed from acid or neutral solution on such agents as frankonite, fuller's earth, and certain zeolites, and eluted with acetone or pyridine solutions.|For more Other Experimental Properties (Complete) data for Riboflavin (6 total), please visit the HSDB record page.

Dust explosion possible if in powder or granular form, mixed with air.

UN1230 - class 3 - PG 2 - Methanol, solution

1

11-23/24/25-39/23/24/25

24/25-45-36/37-16

VJ1400000

F,T

Stable, but light-sensitive. Incompatible with strong oxidizing agents, reducing agents, bases, calcium, metallic salts. May be moisture sensitive.

SRP: Expired or waste pharmaceuticals shall carefully take into consideration applicable DEA, EPA, and FDA regulations. It is not appropriate to dispose by flushing the pharmaceutical down the toilet or discarding to trash. If possible return the pharmaceutical to the manufacturer for proper disposal being careful to properly label and securely package the material. Alternatively, the waste pharmaceutical shall be labeled, securely packaged and transported by a state licensed medical waste contractor to dispose by burial in a licensed hazardous or toxic waste landfill or incinerator.|SRP: At the time of review, regulatory criteria for small quantity disposal are subject to significant revision, however, household quantities of waste pharmaceuticals may be managed as follows: Mix with wet cat litter or coffee grounds, double bag in plastic, discard in trash.|SRP: Criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

Certification of this color additive when used as a food is not necessary for the protection of the public health and therefore batches thereof are exempt from the requirements of section 706(c) of the Federal Food, Drug, and Cosmetic Act.|Substance added directly to human food affirmed as generally recognized as safe (GRAS).|Drug products containing certain active ingredients offered over-the-counter (OTC) for certain uses. A number of active ingredients have been present in OTC drug products for various uses, as described below. However, based on evidence currently available, there are inadequate data to establish general recognition of the safety and effectiveness of these ingredients for the specified uses: riboflavin is included in weight control drug products.|Riboflavin used as a nutrient and/or dietary supplement in animal drugs, feeds, and related products is generally recognized as safe when used in accordance with good manufacturing or feeding practice.

NAS, Food and Nutrition Board, Institute of Medicine; Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. National Academy Press, Washington, D.C. (1998).[Available from, as of March 2, 2010: http://www.nap.edu/catalog/6015.html]

Combustible. Gives off irritating or toxic fumes (or gases) in a fire. Finely dispersed particles form explosive mixtures in air.

Not Classified

Use coarse water spray, carbon dioxide.

Sweep spilled substance into covered containers. If appropriate, moisten first to prevent dusting.

Well closed.

A nuisance-causing concentration of airborne particles can be reached quickly when dispersed.

NO open flames. Closed system, dust explosion-proof electrical equipment and lighting. Prevent deposition of dust.

PREVENT DISPERSION OF DUST!

Use local exhaust or breathing protection.

Protective gloves.

Wear safety spectacles.

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.

LD50 Rat oral > 10,000 mg/kg|LD50 Rat ip 560 mg/kg|LD50 Rat sc 5000 mg/kg

Diseases such as cancer, cardiac disease, and diabetes mellitus are known to precipitate or exacerbate riboflavin deficiency.|Although a number of reports indicate that women taking high-dose oral contraceptives have impaired riboflavin status, no difference was seen when dietary riboflavin intake was controlled.|As with other B vitamins, persons undergoing hemodialysis or peritoneal dialysis and those with severe malabsorption are likely to require extra riboflavin.|Sixty-four migraine /patients/ completed a 4-month open trial with riboflavin (400 mg QD) and were genotyped blindly for mitochondrial DNA (mtDNA) haplogroups. RESULTS: Forty patients responded to riboflavin treatment and 24 were nonresponders. The mtDNA haplogroup H was found in 29 subjects (20 migraine without aura, 9 migraine with aura). Riboflavin responders were more numerous in the non-H group (67.5%). Conversely, nonresponders were mostly H (66.7%). The difference between the two groups was significant (chi(2) = 7.07; p = 0.01). The presence of aura had no influence on riboflavin's effectiveness (chi(2) = 0.113; p = 0.74) and was not associated with a particular haplogroup (chi(2) = 0.55; p = 0.46). In this pharmacogenetic study, riboflavin appears to be more effective in patients with migraine with non-H mitochondrial DNA haplotypes. The underlying mechanisms are unknown, but could be related to the association of haplogroup H with increased activity in complex I, which is a major target for riboflavin. /These/ results may have ethnic implications, since haplogroup H is chiefly found in the European population.

Nutritional factor found in milk, eggs, malted barley, liver, kidney, heart, leafy vegetables. Richest natural source is yeast. Minute amounts present in all plant and animal cells. Occurs in free form only in retina of the eye, in whey, and in urine; Bioactive forms occurring in tissues and cells are riboflavin monophosphate and flavine-adenine dinucleotide.

No difference in riboflavin content of human milk was found between supplemented and unsupplemented well-nourished mothers at 6 months postpartum. Previously, estimates of the riboflavin content of human milk from well-nourished, unsupplemented mothers included 0.37 +/- 0.13 (standard deviation) mg/L at 5 to 7 days postpartum, 0.49 +/- 0.12 mg/L at 43 to 45 days postpartum, 0.24 +/- 0.35 mg/L at 6 months postpartum, and 0.35 +/- 0.02 mg/L after 3 weeks postpartum. More recent studies in five subjects showed that riboflavin in milk may have been previously underestimated as a result of a lack of detection of flavin-adenine dinucleotide (FAD), ... On the basis of this and studies of microbiologically determined riboflavin in human milk, a riboflavin concentration of 0.35 mg/L will be used for human milk consumed by infants younger than 6 months.

NIOSH (NOES Survey 1981-1983) has statistically estimated that 74,790 workers (35,023 of these were female) were potentially exposed to riboflavin in the US(1). Occupational exposure to riboflavin may occur through inhalation and dermal contact with this compound at workplaces where riboflavin is produced or used. The general population is exposed to riboflavin via the ingestion of food(SRC).

Vitamin B refers to several water soluble vitamins often found together in foods, all of which are necessary for normal growth and metabolism, but none of which are synthesized in adequate amounts by humans. The common forms of vitamin B include vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine) and B12 (cyanocobalamin). Except for niacin (when given in high doses), there is no evidence that the other B vitamins, in physiologic or even super-physiologic high doses cause liver injury or jaundice. The major forms of vitamin B and selected other water soluble vitamins (biotin, pantothenic acid, choline) are discussed briefly in this record.

Vitamins

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.

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.

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.

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.

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

Riboflavin is converted to 2 coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are necessary for normal tissue respiration. Riboflavin is also required for activation of pyridoxine, conversion of tryptophan to niacin, and may be involved in maintaining erythrocyte integrity.|Riboflavin functions as the coenzyme for flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which primarily influence hydrogen transport in oxidative enzyme systems (eg, cytochrome C reductase, succinic dehydrogenase, xanthine oxidase).|Two active forms of riboflavin exist ... coenzyme flavin mononucleotide (FMN) and coenzyme flavin adenine dinucleotide (FAD). They are formed by reaction of riboflavin with 1 and 2 molecules of ATP as follow: riboflavin + ATP = riboflavin-P (FMN) + ADP; FMN + ATP = riboflavin-ADP (FAD) + PP.|Riboflavin is a water-soluble, yellow, fluorescent compound. The primary form of the vitamin is as an integral component of the coenzymes flavin mononucleotide (FMN) and flavin-adenine dinucleotide (FAD). It is in these bound coenzyme forms that riboflavin functions as a catalyst for redox reactions in numerous metabolic pathways and in energy production. ... The redox reactions in which flavocoenzymes participate include flavoprotein-catalyzed dehydrogenations that are both pyridine nucleotide (niacin) dependent and independent, reactions with sulfur-containing compounds, hydroxylations, oxidative decarboxylations (involving thiamin as its pyrophosphate), dioxygenations, and reduction of oxygen to hydrogen peroxide. There are obligatory roles of flavocoenzymes in the formation of some vitamins and their coenzymes. For example, the biosynthesis of two niacin-containing coenzymes from tryptophan occurs via FAD-dependent kynurenine hydroxylase, an FMN-dependent oxidase catalyzes the conversion of the 5'-phosphates of vitamin B6 to coenzymic pyridoxal 5'-phosphate, and an FAD-dependent dehydrogenase reduces 5,10-methylene-tetrahydrofolate to the 5'-methyl product that interfaces with the B12-dependent formation of methionine from homocysteine and thus with sulfur amino acid metabolism.|For more Mechanism of Action (Complete) data for Riboflavin (7 total), please visit the HSDB record page.

Fresh air, rest.

Rinse and then wash skin with water and soap.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

/SRP:/ Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR if necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on the left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Poisons A and B/|/SRP:/ Basic treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if needed. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 mL/kg up to 200 mL of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . Cover skin burns with dry sterile dressings after decontamination ... . /Poisons A and B/|/SRP:/ Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Consider administering a beta agonist such as albuterol for severe bronchospasm ... . Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam or lorazepam ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Poisons A and B/

/SIGNS AND SYMPTOMS/ No adverse effects associated with riboflavin consumption from food or supplements have been reported. ... The apparent lack of harm resulting from high oral doses of riboflavin may be due to its limited solubility and limited capacity for absorption in the human gastrointestinal tract; /and/ its rapid excretion in the urine.|/CASE REPORTS/ A previously healthy 15-year-old boy... /developed anaphylaxis/ ... several times after he drank one soft drink or took a single multivitamin tablet .... In an outpatient clinic with the availability of complete resuscitative procedures, ... single-blind prick skin tests and intradermal skin tests /were performed/ on the patient with various pure vitamin components of the soft drink and the multivitamin tablet. Physiologic saline and histamine were used for negative and positive controls, respectively. RESULTS: Riboflavin, a component of both the soft drink and the vitamin tablet, produced positive reactions on intradermal skin tests in the patient. Positive reactions were not present in the normal control subjects. CONCLUSIONS: ... Free-form riboflavin may potentially be associated with an anaphylactic reaction...|/EPIDEMIOLOGY STUDIES/ ... Associations among intake of folate, vitamin B2, vitamin B6, vitamin B12, and polymorphisms of 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) genes and breast cancer risk /were investigated/ in a Japanese population. A hospital based, case-control study was conducted in Nagano Prefecture, Japan, in 388 pairs of patients with histologically confirmed invasive breast cancer and age- and area-matched controls selected from medical checkup examinees. Energy-adjusted intakes of folate and other B vitamins were derived from a validated food frequency questionnaire. Genotyping was completed for MTHFR (C677T and A1298T) and MTR (A2756G). Odds ratios and 95% confidence intervals were calculated by the conditional logistical regression model. Median dietary folate intake (ug/day) in the control group was 438.2 (interquartile range: 354.9-542.9). Neither dietary intake of folate, vitamin B2, vitamin B6, or vitamin B12 nor polymorphisms of MTHFR or MTR genes were significantly associated with breast cancer risk. Further, no significant interaction was found among nutrients, polymorphisms, and breast cancer risk. Associations of nutrients with breast cancer risk did not differ by hormone receptors status. ... Dietary intake of folate and related B vitamins and genotypes of MTHFR or MTR /had/ no overall association with breast cancer risk in Japanese women.|/EPIDEMIOLOGY STUDIES/ ... A case-control study /was conducted/ to investigate the association of nutrient intake involved in the one-carbon pathway of folate for DNA methylation and DNA synthesis and the related enzyme genetic polymorphisms with colorectal cancer. Cases were 107 patients newly diagnosed with colorectal cancer. Controls were 224 subjects matched with cases by sex, age, and residential area. Nutrient intake was assessed by a self-administered, semiquantitative food-frequency questionnaire. Four genetic polymorphisms-MTHFR C677T and A1298C, MTRR A66G, and ALDH2 Glu487Lys-were determined using blood samples. Odds ratios were calculated using conditional logistic regression analysis adjusted for smoking, alcohol consumption, body mass index, and dietary fiber intake. Although folate intake was inversely associated with colorectal cancer, this association was attenuated after further controlling for dietary fiber intake. Neither vitamin B6, vitamin B12, nor vitamin B2, nor any genetic polymorphism was significantly associated with colorectal cancer...|For more Human Toxicity Excerpts (Complete) data for Riboflavin (7 total), please visit the HSDB record page.

The substance can be absorbed into the body by ingestion.

Cough. Sore throat.

Redness. Pain.

Bulk: Powder. Oral: Tablets 25 mg, 50 mg, 100 mg. (Available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name.)

Riboflavin: ACTIVE|The rumen microbial flora are a rich source of vitamins to the ruminant, and that the fecal bacterial flora are a major vitamin source for coprophagic rodents. There is also good evidence that the gut bacterial flora are a significant source of a range of vitamins to the human. In this paper evidence is presented that gut bacteria are a significant source of a range of vitamins, particularly those of the B group and vitamin K.|Recommended daily dietary allowance of Food and Nutrition Board ... is 0.4 to 0.6 mg for infants, 0.8 to 1.2 mg for children up to 10 yr, 1.2 to 2.8 mg for adolescents and adults, and slightly higher for women during pregnancy and lactation.|Minimal requirement for riboflavin to prevent clinical signs of deficiency appears to be less than 0.35 mg/1000 kcal.|... Widely distributed in nature, in ... plants and animals as an essential constituent of all living cells, and is therefore widely distributed in small amounts in foods.|Commercial ... distiller's residues (indirectly from dextrose, lactose, yeast, and whey)

Method: AOAC 981.15; Procedure: automated method; Analyte: riboflavin; Matrix: food and vitamin proparations; Detection Limit: not provided.|Method: AOAC 940.33; Procedure: turbidimetric and titrimetric methods; Analyte: riboflavin; Matrix: vitamin preparations; Detection Limit: not provided.|Method: AOAC 960.46; Procedure: titrimetric and turbidimetric microbiological method; Analyte: riboflavin; Matrix: foods; Detection Limit: not provided.|Method: AOAC 985.31; Procedure: fluorometric method; Analyte: riboflavin; Matrix: infant formula/ready-to-feed milk-based infant formula; Detection Limit: not provided.|For more Analytic Laboratory Methods (Complete) data for Riboflavin (9 total), please visit the HSDB record page.

One of the most commonly used methods for assessing riboflavin status involves the determination of erythrocyte glutathione reductase (EGR) activity. The EGR value is an enzymatic and hence functional indicator that is conventionally determined with and without the addition of flavin-adenine dinucleotide (FAD) -the coenzyme required for the activity of EGR. Results are expressed as an activity coefficient (EGRAC), which is the ratio of activities in the presence of added FAD and without its addition. An EGRAC ratio of 1.0 indicates no stimulation by FAD and the presence of holoenzyme only, which means that more than adequate amounts of FAD (and riboflavin) were present in the original erythrocytes.|Erythrocyte flavin has been used as an indicator of the cellular concentration of the vitamin in its coenzyme forms because these coenzymes comprise over 90 percent of flavin. Because of the instability of the predominant flavin-adenine dinucleotide (FAD), which is rapidly hydrolyzed enzymatically when cells rupture, erythrocyte flavins are deliberately hydrolyzed and measured either microbiologically or fluorometrically as riboflavin. Values greater than 400 nmol/L (15 ug/100 mL) of cells are considered adequate (based on other observations and measurements) and values below 270 nmol/L (10 ug/100 mL) reflect deficiency. Because the margin of difference between adequacy and inadequacy is rather small, there is some concern about the sensitivity and interpretation of results. After mild hydrolysis to convert FAD to the more stable flavin mononucleotide (FMN), high-performance liquid chromatography (HPLC) separation leads to a more exact determination of FMN plus traces of riboflavin. This is a useful indicator that reflects the functional, cellularly trapped forms of riboflavin.

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