Absorption, Distribution and Excretion
Excretion of oral (14)C-coumarin has been reported to vary across species. Within 4 days, rats excreted 47% of the marker in urine and 39% in feces; while rabbits excreted 92% in urine and negligible in feces. In female rabbits, after oral administration of 50 mg/kg 3-14C-coumarin, over 80% of the marker was excreted in urine within 24 hours. No marker was found in exhaled breath, and only a small amount was found in feces. The significant excretion of 14C in feces after oral administration of 14C-coumarin in rats is likely due to unabsorbed substances.
Twenty-four hours after intraperitoneal injection of 14C-coumarins in rats, 38% was excreted in urine, 13% in feces, 30% as 14C-carbon dioxide, and the remaining 9% was mainly found in the cecum.
For more complete data on the absorption, distribution, and excretion of 14 coumarins, please visit the HSDB record page.
Metabolism/Metabolites
…Recombinant human CYP1A and recombinant human CYP2E1 effectively catalyze the formation of coumarin-3,4-epoxide (CE). In mouse, rat, and human liver microsomes, co-inhibition of CYP1A1/2 and CYP2E1 antibodies blocked CE formation by 38%, 84%, and 67% to 92%, respectively (n=3 independent samples). Although CYP1A and 2E appear to be the most active catalysts for CE generation in the liver, studies using the mechanism-based inhibitor 5-phenylpentyne have shown that CYP2F2 is responsible for up to 67% of CE generation in mouse lung microsomes. Unlike the CE pathway, coumarin 3-hydroxylation is a minor coumarin product in mouse, rat, and human liver microsomes, primarily catalyzed by CYP3A and CYP1A, confirming that CE and 3-hydroxycoumarin are formed via different metabolic pathways. To investigate species differences in CYP2A function, we examined the ability of liver microsomes from nine mammals (rats, mice, hamsters, rabbits, guinea pigs, cats, dogs, cynomolgus monkeys, and humans) to catalyze testosterone 7α- and 15α-hydroxylation and coumarin 7-hydroxylation. Antibodies against rat CYP2A1 were able to recognize one or more proteins in the liver microsomes of all the mammals examined. However, the rates of testosterone 7α- and/or 15α-hydroxylation catalyzed by liver microsomes from cats, dogs, cynomolgus monkeys, and humans were negligible. 15α-hydroxylation was most active in human liver microsomes, while the rates of coumarin 7-hydroxylation catalyzed by rat and cat liver microsomes were negligible. The proportion of 7-hydroxycoumarin produced among coumarin metabolites generated by liver microsomes varied among different species. In humans and monkeys, 7-hydroxycoumarin was the major metabolite (>70%), but only a minor metabolite (<1%) in rats. The 7-hydroxylation of coumarin in human liver microsomes was catalyzed by a single high-affinity enzyme (Km 0.2–0.6 μM, which was significantly inhibited by anti-rat CYP2A1 antibody (>95%)). The rate of coumarin 7-hydroxylation varied by approximately 17-fold in the liver microsomes of the 22 subjects. This difference was highly correlated with inter-individual differences in CYP2A6 levels (r² = 0.956). These results indicate that CYP2A6 is primarily or entirely responsible for catalyzing the 7-hydroxylation of coumarins in human liver microsomes. Treatment of monkeys with phenobarbital or dexamethasone increased the activity of coumarin 7-hydroxylase, while treatment with β-naphthylflavonoids resulted in a slight decrease in its activity. Unlike rats and mice, there was no sex difference in CYP2A6 expression in cynomolgus monkeys and humans. Although the anticoagulants dicoumarol and warfarin are structurally similar to coumarins, they do not appear to be substrates of CYP2A6. .../Rats can/hydroxylate coumarins at position 3. Rabbits can also... The liver enzyme system coumarin-7-hydroxylase is responsible for the hydroxylation of most coumarins in cats, guinea pigs, hamsters, rabbits, and especially... In humans, coumarins are absent in the livers of ferrets, mice, and rats. Rat livers contain inhibitors of this enzyme. For more complete data on the metabolism/metabolites of coumarins (15 metabolites in total), please visit the HSDB record page. Known human metabolites of coumarins include 3-hydroxycoumarin, 7-hydroxycoumarin, and coumarin 3,4-epoxide.

Toxicity Summary
Identification: Coumarins are found in the fruits, roots, bark, stems, leaves, and branches of various plants, including tonka bean, cassia seed, lavender, angelica, alfalfa, deer tongue grass, and clover. It is used as a food flavoring agent; a fixative and flavor enhancer in essential oils in perfumes; in soaps, toothpaste, and hair care products; in tobacco products to enhance and fix their natural taste, flavor, and aroma; and in industrial products to mask unpleasant odors. Human Exposure: Four male and four female volunteers each received 200 mg of coumarin capsules. The majority of the dose was excreted within the first 24 hours, primarily as 7-hydroxycoumarin and another metabolite, o-hydroxyphenylacetic acid. Blood concentration-time curves calculated after oral or intravenous administration of coumarin to four male and two female adults showed an open two-compartment model. The primary site of coumarin metabolism is the liver, and glucuronidation of its metabolites can occur in multiple sites, including the liver, intestinal wall, and other tissues. Animal experiments: Administration of coumarin to female albino rats induced hyperglycemia lasting approximately 24 hours. Oral administration of peanut oil-soluble coumarin to unmated female Wistar rats for 7 consecutive days resulted in decreased serum progesterone levels. Six male rats were divided into groups and administered peanut oil-soluble coumarin by gavage for 7 consecutive days. No increase in relative liver weight was observed in the low-dose group; however, a dose-dependent increase in relative liver weight was observed in the highest-dose group. Histological changes in the highest-dose group included steatosis and vacuolar degeneration of central lobular hepatocytes. Both highest-dose groups resulted in the loss of central lobular G6P and aniline hydroxylase. Lysosomal and ultrastructural changes were also observed in both highest-dose groups; the latter manifested as hypertrophy and dilation of the rough endoplasmic reticulum in central lobular hepatocytes, increased lysosomal volume, and an increased number of autophagic vacuoles. Cytochrome P-450 and aminopyridine demethylase activities were also decreased in a dose-dependent manner in both highest-dose groups. Coumarin was added to the diet of DBA/2 and CH3/HeJ mice and fed for 32 weeks. Slight increases in serum aspartate aminotransferase, gamma-glutamyl transferase, and sorbitol dehydrogenase activities were observed, but no gross or microscopic liver lesions were observed. The study found that coumarin could inhibit UV-induced UV repair in E. coli. Coumarin was added to the diet of pregnant mice from days 6 to 17 of gestation. Although delayed ossification and increased stillbirth rate were observed in the high-dose group, no increase in malformation rate was observed at any dose. Three male and three female Osborn-Mendel rats were divided into groups and fed a coumarin-containing diet for four weeks. Significant growth retardation, testicular atrophy, and mild to moderate liver damage were observed. Liver damage manifested as cell death and near-death experiences, eosinophilic and cytoplasmic reduction in central lobular cells, and bile duct hyperplasia. One male and one female dog were given coumarin capsules 6 days a week for 16 consecutive days. Male dogs were euthanized after 9 days due to their critical condition, and female dogs were found dead on day 16. The livers were yellow and nutmeg-like in appearance. Microscopic examination revealed significantly disordered hepatic lobule structure, moderately enlarged hepatocytes with vacuolation, diffuse distribution of abundant fat, focal necrosis, fibrosis, and mild to moderate bile duct hyperplasia. The spleen was pale, the bone marrow was thin with fat accumulation, and the gallbladder was moderately dilated. Four to eight male baboons of different breeds were grouped and fed coumarin-supplemented diets for two years. No changes in body weight were observed. The high-dose group showed an increase in relative liver weight. No treatment-related histological changes in liver specimens were observed at 6 to 10 months. No bile duct hyperplasia or fibrosis was observed in any of the dose groups. Significant dilation of the endoplasmic reticulum was observed in the liver ultrastructure of the three high-dose group animals. [

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Interactions
Coumarin is a moderate inhibitor of 7,12-dimethylbenzo[a]anthracene-induced rat mammary tumors. It also inhibits benzo[a]pyrene-induced mouse forestomach tumors.
This study investigated the potential of coumarin pretreatment to inhibit the genotoxicity of benzo[a]pyrene in ICR mice. Male and female mice weighing 21–24 g were administered coumarin dissolved in olive oil by gavage at doses of 65 g/kg or 139 mg/kg body weight, respectively. The control group received only olive oil. Animals were treated daily for one week with a one-day rest period. After six treatments, animals were injected with benzo[a]pyrene (150 mg/kg, dissolved in olive oil). Micronuclei were examined in polychromatic erythrocytes in bone marrow smears at different time points (12–72 hours) following benzo[a]pyrene injection. Coumarin pretreatment alone did not induce micronucleus formation in polychromatic erythrocytes of both male and female mice. In male mice treated with coumarin before receiving benzo[a]pyrene treatment, the number of micronuclei in polychromatic erythrocytes was significantly reduced. To clarify that this reduction was not due to a phase shift in the onset of micronucleus formation, we investigated at different time intervals after benzo[a]pyrene injection. The results showed that coumarin alone did not induce micronucleus production, while the number of benzo[a]pyrene-induced micronuclei was significantly reduced in male mice pretreated with coumarin. This protective effect of coumarin pretreatment was not observed in female animals. The following medications may enhance the response to coumarin or indanedione derivatives: alcohol (acute poisoning), allopurinol, aminosalicylic acid, amiodarone, anabolic steroids, chloral hydrate, chloramphenicol, cimetidine, clofibrate, trimethoprim-sulfamethoxazole, danazol, dexthylexin sodium, diazoxide, diflunisal, disulfiram, erythromycin, ethacrynic acid, fenoprofen calcium, glucagon, ibuprofen, indomethacin, influenza vaccine, isoniazid, meclofenamic acid, mefenamic acid, methylthiouracil, metronidazole, miconazole, nalidixic acid, neomycin (oral), pentoxifylline, phenylbutazone, propoxyphene, propylthiouracil, quinidine, quinine, salicylates, streptokinase, sulfinpyrazone, sulfonamides, sulindac, tetracyclines, thiazide diuretics, thyroid medications, tricyclic antidepressants, urokinase, vitamin E. /Coumarins and Indanedione Derivatives/
The following drugs...may...reduce...the response to coumarin or indanedione derivatives: alcohol (chronic alcoholism), barbiturates, carbamazepine, corticosteroids, adrenocorticotropic hormone, ethylclofenac, glutamine, griseofulvin, mercaptopurine, methylquinone, estrogen-containing oral contraceptives, rifampin, spironolactone, vitamin K. /Coumarins and Indanedione Derivatives/

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Non-human Toxicity Values
Oral LD50 in rats: 293 mg/kg
Oral LD50 in mice: 196 mg/kg
Intraperitoneal LD50 in mice: 220 mg/kg
Subcutaneous LD50 in mice: 242 mg/kg
Oral LD50 in guinea pigs: 202 mg/kg

[1]. Biomed Chromatogr. 2011 Jul;25(7):7

Coumarin is a colorless crystal, flake, or colorless to white powder with a pleasant vanilla aroma and a bitter, aromatic, pungent taste. (NTP, 1992)
Coumarin is a chromone ketone compound with its ketone group located at the 2-position. It can be used as a fluorescent dye, plant metabolite, and human metabolite.
Coumarin has been reported to be found in Caragana frutex, Eupatorium japonicum, and several other organisms with relevant data.
Coumarin is a hydroxycinnamic acid. It is an aromatic compound found in many plants, released when the plant wilts. It has anticoagulant activity by competing with vitamin K.
Coumarin is a chemical compound/toxin found in many plants, particularly in tonka bean, sage, and buffalo grass. It has a sweet aroma and is easily identified as the scent of freshly cut hay. It has clinical value and is a precursor to several anticoagulants, especially warfarin. —Wikipedia Coumarin compounds are a class of naturally occurring benzo-α-pyranone compounds with important and diverse physiological activities. Their parent compounds, coumarins, are naturally found in many plants, natural spices, and foods, such as tonka bean, cinnamon (also known as Chinese cinnamon), cassia bark, sweet clover, green tea, mint, celery, blueberry, lavender, honey (derived from sweet clover and lavender), and carrots, as well as in beer, tobacco, wine, and other foods. The concentrations of coumarins in these plants, spices, and foods range widely, from <1 mg/kg in celery to 7000 mg/kg in cinnamon, and 87000 mg/kg in cassia bark. It is estimated that humans ingest 0.02 mg/kg/day of coumarins through diet. Coumarins are used as additives in perfumes and fragrances, with concentrations ranging from <0.5% to 6.4% in high-end perfumes to <0.01% in detergents. Assuming coumarin can be completely absorbed through the skin, the estimated systemic coumarin intake in humans through fragrances and cosmetics is 0.04 mg/kg body weight/day. In 1954, the U.S. Food and Drug Administration (FDA) banned the use of coumarin as a food additive based on reports of hepatotoxicity in rats. Given the potential hepatotoxicity of coumarin in humans, the European Commission limits the direct addition of coumarin to natural foods to 2 mg/kg food/day, but higher levels are permitted in alcoholic beverages, caramel, chewing gum, and certain "conventional foods." Besides dietary and consumer product intake, coumarin is used clinically as an anti-tumor drug and to treat lymphedema and venous insufficiency. The intake range of coumarin is wide, from 11 mg daily from natural food ingredients to 7 g daily after clinical administration. Although adverse reactions following coumarin exposure in humans are rare and only related to clinical doses, recent evidence suggests that coumarin can cause liver tumors in rats and mice, and Clara cell toxicity and lung tumors in mice. The multiple effects of coumarins and ongoing human exposure have spurred significant research efforts to understand the mechanisms of coumarin-induced toxicity/carcinogenicity and their relevance to humans. These studies have revealed significant species differences in coumarin metabolism and toxicity, leading to a deeper understanding of the mechanisms of action of coumarins in rodents and their implications for safety assessment of human coumarin exposure. In October 2004, the European Food Safety Authority (EFSA, 2004) reviewed coumarins to determine their tolerable daily intake (TDI) in food. EFSA issued an opinion stating that coumarins are not genotoxic and that a threshold method is most appropriate for safety assessment. EFSA recommended a TDI of 0 to 0.1 mg/kg body weight/day. Considering dietary intake, the estimated total human exposure is 0.06 mg/kg/day. As a medicine, coumarins have been used for various purposes and have multiple dosing regimens. Unlike warfarin and other coumarin derivatives, coumarins do not have anticoagulant activity. However, low doses (typically 7 to 10 mg/day) of coumarin can be used as a “venous dilator” to promote venous health and venous blood flow. Additionally, coumarin is used clinically to treat high-protein lymphedema of various etiologies (A7913).
See also: Cinnamon (partial); Chinese Cinnamon (partial); Chinese Cinnamon Leaf Oil (partial)...See more...

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Mechanism of Action
Coumarins and some of their metabolites have been shown to inhibit glucose-6-phosphatase in the liver and liver microsomes. It interferes with the excision repair process of UV-damaged DNA and interferes with the host cell reactivation of UV-irradiated bacteriophage T1 in E. coli WP2.
4-Hydroxycoumarin derivatives and indanedione (also known as oral anticoagulants) are both vitamin K antagonists. Their use as rodenticides works by inhibiting vitamin K-dependent steps in the synthesis of various blood clotting factors. Vitamin K-dependent proteins in the coagulation cascade include procoagulant factors II (prothrombin), VII (prothrombin convertase), IX (Christmas factor), and X (Stuart-Proll factor), as well as coagulation inhibitory proteins C and S. All of these proteins are synthesized in the liver. Before being released into the bloodstream, these precursor proteins undergo numerous (intracellular) post-translational modifications. Vitamin K acts as a coenzyme in one of these modifications, specifically by carboxylating 10–12 glutamate residues to γ-carboxyglutamate (Gla) at a specific site. The presence of these Gla residues is crucial for the procoagulant activity of various coagulation factors. Vitamin K hydroquinone (KH2) is the active coenzyme, whose oxidation to vitamin K 2,3-epoxide (KO) provides the energy required for the carboxylation reaction. The epoxide is then recycled through a two-step reduction reaction catalyzed by KO reductase… KO reductase is the target of coumarin anticoagulants. Coumarin anticoagulants inhibit KO reductase activity, leading to rapid depletion of KH2 supply and effectively preventing the formation of Gla residues. This results in the accumulation of uncarboxylated clotting factor precursors in the liver. In some cases, these precursors are further processed without carboxylation and (depending on the species) may appear in the bloodstream. At this point, the uncarboxylated protein is called decarboxylated clotting factor. Normal clotting factors circulate as proenzymes, participating in the coagulation cascade only after activation through limited proteolytic degradation. Decarboxylated clotting factors lack procoagulant activity (i.e., cannot be activated) and cannot be converted to active proenzymes by the action of vitamin K. High levels of circulating decarboxylated clotting factors can be detected in humans receiving anticoagulation therapy, while levels of these factors are negligible in rats and mice treated with warfarin. /Anticoagulant rodenticides/

C9H6O2

146.15

146.036

C, 73.97; H, 4.14; O, 21.89

91-64-5

Coumarin-d4;185056-83-1

323

White to off-white solid powder

1.2±0.1 g/cm3

298.0±0.0 °C at 760 mmHg

68-73 °C(lit.)

118.3±16.1 °C

0.0±0.6 mmHg at 25°C

1.595

1.39

0

2

0

11

196

0

O=C1C=CC2C(=CC=CC=2)O1

ZYGHJZDHTFUPRJ-UHFFFAOYSA-NZYGHJZDHTFUPRJ-UHFFFAOYSA-N

InChI=1S/C9H6O2/c10-9-6-5-7-3-1-2-4-8(7)11-9/h1-6H

2H-1-Benzopyran-2-one

Coumarin; NSC 8774; NSC-8774; NSC8774

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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

DMSO : 29 ~100 mg/mL (198.43 ~684.28 mM )
Ethanol : ~29 mg/mL
H2O : ~4 mg/mL (~27.37 mM)

Solubility in Formulation 1: ≥ 3 mg/mL (20.53 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 3 mg/mL (20.53 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 3 mg/mL (20.53 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 8.33 mg/mL (57.00 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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