Mouse microsomes activate MeIQx (0.47 mM; 0-120 min) to produce metabolites through covalent binding to mouse hemoglobin [1].

MeIQx (2.0-200 mg/kg; i.p.; male Swiss Webster mice) covalently binds to hemoglobin in a dose-dependent manner [1].

Animal/Disease Models: Male Swiss Webster mouse [1]
Doses: 2.0-200 mg/kg
Route of Administration: intraperitoneal (ip) injection
Experimental Results: Increased covalent binding to hemoglobin in a dose-dependent manner.

Absorption, Distribution and Excretion
High-temperature cooking of meat, fish, or poultry produces heterocyclic aromatic amines (HAAs), which can be metabolically activated into mutagenic or carcinogenic intermediates. Cytochrome P4501A2 (CYP1A2) and N-acetyltransferase (NAT2) are primarily involved in these biotransformations… This study determined the relationship between the activities of these two enzymes and the urinary excretion of unmetabolized products and phase II conjugates of two HAAs, MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), in individuals consuming a homogeneous diet containing high-temperature cooked meat. Participants in this study consumed meat containing known amounts of MeIQx and PhIP, and urine samples were collected at 0–12 hours and 12–24 hours postprandial. Acid treatment was used to quantitatively hydrolyze the conjugates II, hydrolyzing MeIQx and PhIP into their corresponding parent amines, followed by determination of MeIQx and PhIP levels in urine. Extracts containing heterocyclic amines (HAAs) were purified by immunoaffinity chromatography and analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry. After acid hydrolysis, the MeIQx content in urine increased 3-21 times in the 0-12 hour postprandial period. After acid treatment, the total amount of MeIQx excreted in urine in the 0-12 hour period (unmetabolites and their N2-glucuronide and sulfamate metabolites) was 10.5 ± 3.5% (mean ± standard deviation) of the administered dose, while the total amount of PhIP (unmetabolites and their acid-labile conjugates) was 4.3 ± 1.7% (mean ± standard deviation) of the administered dose. The total amount of PhIP in urine in the 12-24 hour period after acid treatment was 0.9 ± 0.4% (mean ± standard deviation) of the administered dose. Linear regression analysis of MeIQx and PhIP excretion (expressed as a percentage of ingested dose) over 0–12 hours in all subjects showed a low but significant correlation (r = 0.37, P = 0.005). The analysis revealed that decreased urinary total MeIQx (unmetabolites plus N2-glucuronide and sulfamate metabolites) levels were associated with increased CYP1A2 activity, while urinary total PhIP (unmetabolites plus conjugates) levels were not correlated with CYP1A2 activity. These results suggest that in humans, the metabolism and distribution of MeIQx are more influenced by CYP1A2 activity than PhIP. Linear regression analysis did not find an association between NAT2 activity and urinary excretion levels of either MeIQx or PhIP (unmetabolites plus acid-labile conjugates). This study investigated the distribution kinetics of radiolabeled [2-14]C-IQ (2-amino-3-methylimidazo[4,5-f]quinoline) and [2-14]C-MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) in BALB/c mice after a single oral administration. Both compounds rapidly entered the blood and other tissues after administration, with approximately 20-25% of the radioactive IQ or MeIQx dose excreted in the urine within 6 hours, indicating rapid absorption of these mutagens. The levels of MeIQx isolated from the lungs and blood of treated mice were significantly higher than those of IQ. In studies of quinoxaline (IQ) absorption in the closed intestinal tract, very little IQ was absorbed from the stomach. Although there is evidence that the large intestine can also absorb IQ, the small intestine is the primary site of IQ absorption.
This study investigated the absorption and excretion kinetics of (14)C-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in male Sprague-Dawley rats. Within 72 hours of oral administration of (14)C-MeIQx (20 mg/kg), 33-56% of the radioactive material was excreted in the urine and 37-75% in the feces, representing over 99% of the total dose. Only trace amounts of radioactive material remained in the body. The liver and kidneys showed the highest radioactivity per gram of tissue, with trace amounts also detected in the lungs, small intestine, and large intestine. Within 24 hours, 25% to 50% of the MeIQx dose was recovered in the bile. Bile metabolites were excreted over a prolonged period, with some radioactive material rapidly excreted within 2-3 hours and the remainder within 10-12 hours. Genotoxicity of metabolites in bile was assessed using either liver-activated or unactivated Salmonella typhimurium TA98 via S-9 activation, revealing their presence as detoxification products. The residual mutagenic activity in bile was primarily attributed to unmetabolized MeIQx. This study investigated the distribution and metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in rats. Five male and female rats were given a single oral dose of (14)C-labeled MeIQx (3–4 mg/kg body weight). Within 24 hours of administration, male rats excreted 36% of the radioactive material and 15% of the mutagenic activity in their urine. Female rats excreted 41% of the radioactive material and 12% of the mutagenic activity in their urine. Within the next 48 hours, only 1–3% of the radioactive dose was excreted in the urine. The remaining dose was excreted in the feces, with less than 1% of the radioactive material remaining in tissues after 72 hours. The liver and kidneys retained more radioactivity than other organs. For more complete data on the absorption, distribution, and excretion of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (10 in total), please visit the HSDB record page. Metabolites/Metabolic Substances 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)…and its isotopically labeled ([13]C, [15]N2, and [14]C) analogs were synthesized and used in in vivo metabolic studies. Equimolar mixtures of MeIQx and its [13]C, [15]N2 stable isotopically labeled analogs (containing tracer amounts of [14]C-MeIQx) were intraperitoneally injected into mice. Approximately 67% of the radioactive material was excreted in urine and feces within 24 hours. Urine was analyzed by high-performance liquid chromatography (HPLC), and four radiolabeled substances were observed, corresponding to unmetabolized MeIQx and three more polar metabolites. Urine was directly analyzed by HPLC-HS-MS. Four signals were observed, all containing characteristic 1:1 isotopic doublets, corresponding to unmetabolized MeIQx, MeIQx glucuronide, and two unidentified metabolites.
The formation of adducts is considered to be the main cause of DNA damage caused by carcinogenic heterocyclic amines. We investigated whether the N-hydroxy metabolite of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) caused oxidative DNA damage using (32)P-labeled DNA fragments and an electrochemical detector coupled with HPLC. The study found that the metabolite [MeIQx(NHOH)] could lead to Cu(II)-mediated DNA damage, including the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine. DNA damage was significantly enhanced upon the addition of the endogenous reducing agent β-nicotinamide adenine dinucleotide (NADH). Catalase and the Cu(I)-specific chelator bartophenone inhibited DNA damage, suggesting the involvement of H₂O₂ and Cu(I). In the presence of NADH and Cu(II), MeIQx(NHOH) frequently induced DNA breaks at thymine and cytosine residues. UV-Vis spectroscopy revealed that MeIQx(NHOH) hardly decomposed in the absence of Cu(II); however, a rapid spectral change occurred in the presence of Cu(II), suggesting that Cu(II) catalyzed its auto-oxidation. Upon the addition of NADH, the oxidation product was reduced to MeIQx(NHOH). These results indicate that the copper-peroxide intermediate generated by the reaction of Cu(I) with H₂O₂ participates in the Cu(II)-dependent DNA damage induced by MeIQx(NHOH), and that NADH enhanced this DNA damage through redox cycles. /Conclusion/ In addition to the formation of DNA adducts, oxidative DNA damage also plays an important role in the carcinogenicity of MeIQx. /MeIQx(NHOH)/
2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) is one of the most abundant heterocyclic aromatic amines produced during meat cooking and is genotoxic and carcinogenic to rodents. MeIQx requires P450 metabolic activation to exert these effects. Although there is indirect evidence that the mutagenic product is N-hydroxy-MeIQx (N-OHMeIQx),… this product was definitively identified after incubation of the amine with human liver microsomal fractions. The products were analyzed by high performance liquid chromatography-thermal spray mass spectrometry using unlabeled MeIQx, a mixture of (13C,15N2)MeIQx and (14C)MeIQx as substrates. A characteristic doublet ion was found at m/z 214/217 ([M+H]+) of the parent compound MeIQx, with a difference of 3 mass units; a characteristic doublet ion was also found at m/z 230/233 ([M+H]+) of N-OHMeIQx. The presence of the doublet ion at m/z 214/217 and the doublet [M+H+] at 230/233 further confirms that the compound is N-OHMeIQx, as N-hydroxylamine compounds readily lose the "O" atom. To further determine the identity of the major metabolite (which accounts for approximately 90% of total microsomal metabolism), we compared the mutagenicity of the HPLC eluent against Salmonella Typhimurium YG1024 (particularly sensitive to N-hydroxylamine compounds) and TA98/1,8-DNP6 (resistant to most N-hydroxylamine compounds). 95% of the direct mutagenicity in the reaction mixture was associated with a single peak co-eluted with N-OHMeIQx, as confirmed by mass spectrometry. Only one additional mutagenic peak was detected in the presence of the metabolically activated system, corresponding to unaltered MeIQx. The N-hydroxylation rate of MeIQx (5 μM) in human liver microsomes was 77 ± 11 pmol/mg/min (mean ± standard error, n = 4). Furazolidone (5 μM), a specific inhibitor of human CYP1A2, inhibited the N-hydroxylation of MeIQx by more than 90%. These data indicate that N-OHMeIQx is the major oxidation and genotoxic product of MeIQx generated from human liver microsomal components, and that the reaction is almost entirely catalyzed by CYP1A2. The distribution and metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) were investigated in mice. Following a single oral administration of 20 mg (14)C-labeled MeIQx/kg body weight, three major non-mutagenic metabolites were identified. These were 2-amino-4 (or 5)-(β-D-glucuronylpyranosyl)-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline-4 (or 5)-yl sulfate, and N-(3,8-dimethylimidazo[4,5-f]quinoxaline-2-yl)aminosulfonate. Two additional metabolites were also present in bile, urine, and feces: 2-(β-D-glucuronylpyranosylamino)-3,8-dimethylimidazo[4,5-f]quinoxaline and 2-amino-8-hydroxymethyl-3-methylimidazo[4,5-f]quinoxaline-4 (or 5)-yl sulfate. All metabolites were substantially non-mutagenic. The majority of mutagenicity remaining in bile, urine, and feces is attributable to unchanged MeIQx. Unchanged MeIQx is the most abundant excreted form in urine.
For more complete metabolite/metabolite data on 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (20 metabolites in total), please visit the HSDB record page.
Known human metabolites of MeIQx include IQx-8-COOH and N-hydroxyMeIQX.

[1]. The measurement of MeIQx adducts with mouse haemoglobin in vitro and in vivo: implications for human dosimetry. Carcinogenesis. 1991 Jun;12(6):1067-72.

[2]. Carcinogenicity in mice of a mutagenic compound, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) from cooked foods. 1987 May;8(5):665-8.

According to the International Agency for Research on Cancer (IARC) of the World Health Organization, MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) is a possible carcinogen. MeIQx is an imidazo[4,5-f]quinoxaline compound with the structure 3H-imidazo[4,5-f]quinoxaline, substituted with methyl groups at positions 3 and 8 and an amino group at position 2. It is a mutagenic compound found in cooked beef, exhibiting mutagenic, carcinogenic, genotoxic, and Maillard reaction product properties. It is an imidazo[4,5-f]quinoxaline compound and also an aromatic amine. 8-Methyl-IQX is a synthetic pale orange to brown crystalline solid, soluble in dimethyl sulfoxide and methanol. It is produced in small quantities for research purposes. 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline is naturally formed during the cooking of muscle-based foods (meat and fish). The amount of this chemical formed depends on the cooking temperature, cooking time, and cooking method (direct or indirect). It is one of the most abundant heterocyclic amines in a typical Western diet. 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline is also found in processed food flavorings, beer, wine, and cigarette smoke. It is likely a human carcinogen. (NCI05)
See also: Beef (partial); Cooked salmon (partial); Cooked chicken (partial)... See more...

C11H11N5

213.244

213.101

C, 61.96; H, 5.20; N, 32.84

77500-04-0

MeIQx-d3;122457-31-2

62275

Light yellow to yellow solid powder

1.47 g/cm3

458.4ºC at 760mmHg

> 300ºC

1.776

1.988

1

4

0

16

271

0

CC1=CN=C2C=CC3=C(C2=N1)N=C(N3C)N

DVCCCQNKIYNAKB-UHFFFAOYSA-N

InChI=1S/C11H11N5/c1-6-5-13-7-3-4-8-10(9(7)14-6)15-11(12)16(8)2/h3-5H,1-2H3,(H2,12,15)

3,8-Dimethyl-3H-imidazo(4,5-f)quinoxalin-2-amine

8-Methyl-IQX; MeIQx;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

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.)