DNA (forms covalent adducts, primarily O⁶-alkylguanine and 7-alkylguanine). NMOR is metabolically activated by cytochrome P450 enzymes to reactive intermediates that alkylate DNA bases, leading to mutations and carcinogenesis. It does not target a specific receptor but rather exerts genotoxic effects through DNA damage.

NMOR induces mutagenic effects in bacterial (Ames test) and mammalian cells in a dose-dependent manner. It is positive in the Ames test with metabolic activation (S9 fraction). In vitro, it causes DNA strand breaks, chromosomal aberrations, and sister chromatid exchanges in cultured human lymphocytes and rodent cell lines. It also increases micronucleus formation and induces unscheduled DNA synthesis in hepatocytes.

Tumor models can be created in animals by using N-nitrosomomorpholine.

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NMOR is a potent carcinogen in vivo, inducing tumors in multiple organs including liver, lung, kidney, and nasal cavity in rats, mice, and hamsters after oral, inhalation, or subcutaneous administration. It also promotes preneoplastic lesions and hepatocellular carcinomas in a dose- and time-dependent fashion. Its carcinogenic potency is well established in long-term bioassays, and it serves as a positive control in chemoprevention studies.

Ames test is performed using Salmonella typhimurium strains TA1535 and TA100, with and without rat liver S9 metabolic activation. NMOR is tested at multiple concentrations (0.1-1000 µg/plate) and incubated for 48-72 hours. His+ revertant colonies are counted and compared to spontaneous mutation rates. A positive response (≥2-fold increase) indicates mutagenic potential. DNA adduct formation is quantified by ³²P-postlabeling or LC-MS/MS.

Human peripheral lymphocytes or Chinese hamster ovary (CHO) cells are cultured and exposed to NMOR (0.1-100 µM) for 2-4 hours with S9 mix. Micronucleus frequency is scored in binucleated cells after cytochalasin B block. Alternatively, the comet assay measures DNA strand breaks under alkaline conditions. Cytotoxicity is evaluated by trypan blue exclusion or MTT assay. For gene mutation assays, HPRT locus mutation frequency is determined in CHO or V79 cells.

Long-term carcinogenicity bioassays are conducted in F344 rats or B6C3F1 mice. NMOR is administered in drinking water at doses of 5-100 ppm for up to 104 weeks. Animals are observed daily, weighed weekly, and necropsied at termination. Tissues (liver, lung, kidney, nasal cavity) are processed for histopathological examination to determine tumor incidence and multiplicity. Intermediate biomarkers like hepatic foci are also assessed in short-term (6-week) protocols.

Absorption, Distribution and Excretion
Following intraperitoneal injection of 400 mg/kg body weight of 3C-NMOR in rats, 3.3% of the marker was excreted as 14CO₂ within 24 hours, with 81% excreted in the urine; 24% of the radioactivity was recovered as unchanged NMOR, and 15% as N-nitrosodiethanolamine. Male CD-1 mice were exposed daily for 6 hours at a nominal concentration of 20 ppm of 15N-nitrogen dioxide (15NO₂) for 4 consecutive days, followed by 2 hours of exposure on day 5, and were subsequently administered morpholine by gavage for 5 consecutive days. N-nitrosomorpholine (NMOR) was detected in the whole mouse length, stomach, hairy skin, and remains. ...The average weight of each mouse was 27.6 g, and the total N-nitrosomorpholine content was 3903 ng. The concentration of N-nitrosomorpholine was highest in the skin, followed by the stomach, and lowest in the remains. ...GC-MS analysis was used to distinguish N-nitrosomorpholine derived from (15)N-nitrogen dioxide from other sources. ...In the stomach, 73% was identified as (14)N-nitrosomorpholine, accounting for 1.6% of the total N-nitrosomorpholine in mice; 27% was identified as (15)N-nitrosomorpholine, accounting for 0.6% of the total N-nitrosomorpholine in mice. ...

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Metabolism/Metabolites
Acid hydrolysis of liver RNA and DNA in rats injected intraperitoneally with 400 mg/kg body weight of (3-(14)c)-NMOR yielded six different radioproducts, one of which may be 7-(2-hydroxyethyl)guanine.
N-Nitromorpholine is converted to N-nitroso-2-hydroxymorpholine in rat liver microsomes. The only clearly identified urinary metabolite is N-nitrosodiethanolamine.
After intraperitoneal injection of 400 mg/kg body weight (3-(14)C)-NMOR in rats, 3.3% of the label was excreted as (14)CO2 within 24 hours, and 81% was excreted in urine; 24% of the radioactive material was recovered as unchanged NMOR, and 15% was recovered as N-nitrosodiethanolamine.
In vitro experiments showed that in human acidic gastric juice, small doses of the precursors (sodium nitrite and morpholine) can significantly generate nitrosomorpholine (NMOR). These data suggest that nitrosation may occur in human gastric juice under low-acid and acid-free conditions. ……
Rats metabolize nitrosomorpholine in liver microsomes to generate acetaldehyde, formaldehyde, glyoxal and N-nitroso-2-hydroxymorpholine. Fenton's reagent oxidizes N-nitrosomorpholine to acetaldehyde, glycolaldehyde, glyoxal, (2-hydroxyethoxy)acetaldehyde, and N-nitroso-2-hydroxymorpholine. N-nitroso-3-hydroxymorpholine in water primarily produces acetaldehyde, along with glycolaldehyde, (2-hydroxyethoxy)acetaldehyde, and glyoxal. These observations suggest that 3-hydroxylation may occur during biological and chemical oxidation processes.

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NMOR is rapidly absorbed from the gastrointestinal tract following oral administration. It undergoes extensive first-pass metabolism in the liver via CYP2E1 and CYP2A6 to form reactive intermediates, including alkylating species. The half-life in blood is short (approximately 1-2 hours). Metabolites are excreted primarily in urine as unchanged compound and glucuronide conjugates. Tissue distribution is widespread, with highest levels in liver and kidney.

Toxicity Data
LCLo (mice) = 1,000 mg/m³/10 min

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Interactions Female Sprague-Dawley rats were randomly assigned to four groups (Group 1: Control group, Group 2: Sham-operated group, Group 3: Ovariectomy group, Group 4: Ovariectomy + Estrogen group). All rats received a single intraperitoneal injection of diethylnitrosamine (100 mg/kg body weight), followed by the addition of N-nitrosomorpholine (100 ppm) to their drinking water for 20 weeks to establish a rat hepatocellular carcinoma model. Physiological estrogen was administered using 17α-ethinylestradiol (30 μg/kg body weight), while the sham-operated group rats received saline treatment after the onset of hepatocellular carcinoma. Treatment of ovariectomized animals with 17α-ethinylestradiol (30 μg/kg body weight/day) significantly reduced the incidence, development, and metastasis of hepatocellular carcinoma (HCC) compared to rats that underwent ovariectomy alone, and prolonged the survival time of animals that died before the end of the experiment (p<0.05); however, this difference disappeared compared to the other three groups. This study investigated the effect of cysteamine (2-aminoethanethiol hydrochloride) on the development of N-nitrosomorpholine-induced liver cancer in male Sprague-Dawley rats. Twenty rats were subcutaneously injected with cysteamine every other day and, starting from week 3 of the experiment, drank water containing 250 mg/L NMOR for 8 weeks. The control group (n=20) was subcutaneously injected with physiological saline. By week 18, the body weight and liver weight of all rats treated with cysteamine were slightly higher than those in the sodium chloride treatment group. Histochemical techniques were used to detect precancerous lesions and tumors that were positive for γ-glutamyl transferase or glucose-6-phosphate dehydrogenase staining. At week 18, quantitative histological analysis showed that long-term administration of cysteine significantly reduced the number of γ-glutamyl transferase-positive and glucose-6-phosphate dehydrogenase-positive liver lesions (from 31.4 lesions/cm² in the saline control group to 3 lesions/cm² and 15.9 lesions/cm², respectively). Histologically, compared with the untreated group, the number and size of hepatocellular carcinomas in γ-glutamyl transferase-positive and glucose-6-phosphate dehydrogenase-positive lesions were significantly reduced in the cysteine-treated group. After cysteine administration, the concentration of hepatic norepinephrine and the labeling indices of precancerous lesions and surrounding liver tissue were significantly reduced. This study investigated the effect of 3,4,3',4'-tetrachlorobiphenyl on glucose-6-phosphatase (G6Pase) alterations in the liver of N-nitrosomorpholine-treated B6C3F1 mice. 3,4,3',4'-tetrachlorobiphenyl was selected as a selective 3-methylcholanthrene inducer and tumor promoter. To induce hepatocellular carcinoma, mice were treated with N-nitrosomorpholine (160 mg/L, in drinking water, for 7 weeks) following a previous study in a rat model. After a 22-week treatment-free period, mice were administered 3,4,3',4'-tetrachlorobiphenyl (5 times, 50 mg/kg every 3 days), and liver lesions were analyzed 10 weeks after the start of 3,4,3',4'-tetrachlorobiphenyl treatment. Following 3,4,3',4'-tetrachlorobiphenyl treatment, the number of G6Pase-negative and G6Pase-positive lesions in each liver was significantly reduced (to 32% and 57%, respectively). On the other hand, the average volume of residual G6Pase-altering lesions increased due to the increased proportion of large lesions (greater than 0.5 mm²). Histological examination and elevated serum aspartate aminotransferase (AST) levels confirmed persistent liver injury induced by N-nitrosomorpholine and 3,4,3',4'-tetrachlorobiphenyl treatment during the 39-week experimental period. Unlike the rat model, 3,4,3',4'-tetrachlorobiphenyl exhibited the opposite effect on liver lesions in the mouse model: (a) it had a moderate pro-tumor effect in N-nitrosomorpholine-damaged liver; (b) it had cytotoxic effects, leading to a reduction in the number of liver lesions. The effect of oral fructose on hepatocellular carcinoma was investigated. Hepatocellular carcinoma was induced in male Sprague-Dawley rats by injection of N-nitrosomorpholine for 7 weeks. Afterwards, the animals were divided into two groups: one group received water containing fructose (120 g/L) with free access to food (Group I), and the other group received tap water with free access to food (Group II). Compared with animals treated with N-nitrosomorpholine alone, the incidence of hepatocellular carcinoma in rats treated with N-nitrosomorpholine combined with fructose was 46%, while the incidence of hepatocellular carcinoma in animals treated with N-nitrosomorpholine alone was 24% (P < 0.05). The incidence of other malignancies did not differ significantly between the two groups (Group I: 32.1%, Group II: 32.0%). Morphometric assessment of precancerous liver lesions showed that fructose treatment had an enhancing effect several months before the onset of malignancies. Six weeks after treatment, the proportion of focal lesions in the liver parenchyma increased from 6.7% in animals treated with N-nitrosomorpholine alone to 8.5% in animals treated with N-nitrosomorpholine combined with fructose (P < 0.05). This increase was primarily due to an increase in glycogen storage foci (P < 0.0005). Furthermore, fructose treatment resulted in a detectable increase in glucose-6-phosphatase and glucose-6-phosphate dehydrogenase activity in focally affected hepatocytes and surrounding parenchyma, which was detectable on histochemically. In the N-nitrosomorpholine plus fructose group, intralesional glucose-6-phosphatase activity was generally approximately equal to that in the parenchyma of the untreated control group. For more complete data on interactions of N-nitrosomorpholine (out of 15), please visit the HSDB record page.

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Non-human toxicity values
Rat LD50 (route not specified) 320 mg/kg
Rat intravenous LD50 98 mg/kg
Rat subcutaneous LD50 170 mg/kg
Rat intraperitoneal LD50 282 mg/kg
For more complete data on non-human toxicity of N-nitrosomorpholine (out of 8), please visit the HSDB record page.

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NMOR is highly toxic, with acute oral LD₅₀ in rats about 280 mg/kg. Chronic exposure causes dose-dependent increase in tumor incidence, particularly hepatocellular carcinomas and lung adenomas. It is a potent mutagen and clastogen. IARC classifies it as Group 2B (possibly carcinogenic to humans). Inhalation may cause respiratory irritation. Safety handling requires strict containment and personal protective equipment due to its carcinogenic potential.

[1]. K D Brunnemann, et al. N-Nitrosomorpholine and Other Volatile N-nitrosamines in Snuff Tobacco. Carcinogenesis. 1982;3(6):693-6.

According to an independent committee of scientific and health experts, N-nitrosomorpholine may be carcinogenic. N-nitrosomorpholine is a yellow crystalline solid. At 68°F (approximately 20°C), it is a golden-yellow liquid containing abundant crystals. (NTP, 1992) N-nitrosomorpholine is a nitrosamine, a derivative of morpholine in which the hydrogen atom bonded to the nitrogen atom is replaced by a nitroso group. It is a carcinogen and mutagen, found in snuff. It has carcinogenic and mutagenic effects. N-nitrosomorpholine has no commercial use in the United States. Information on the health effects of N-nitrosomorpholine is limited. Currently, there is no information on the acute (short-term), chronic (long-term), reproductive, developmental, or carcinogenic effects of N-nitrosomorpholine on humans. Animal studies report that long-term exposure to N-nitrosomorpholine can cause liver damage, and oral exposure can lead to tumors in the liver, nasal cavity, lungs, and kidneys. The U.S. Environmental Protection Agency (EPA) has not yet classified N-nitrosomorpholine as a carcinogen. The International Agency for Research on Cancer (IARC) has classified N-nitrosomorpholine as a Group 2B carcinogen, meaning it is possibly carcinogenic to humans. Data already indicates that N-nitrosomorpholine is present in tobacco (Nicotiana tabacum). N-nitrosomorpholine is a photosensitive, yellow crystalline nitrosamine. There is no commercial use or production of N-nitrosomorpholine in the United States. This substance has been found as a contaminant in rubber products, including rubber nipples in baby bottles, and is also present in various vegetables, cheeses, alcoholic beverages, and fruits. N-nitrosomorpholine is likely a human carcinogen. (NCI05)

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NMOR is exclusively a research chemical; it has no therapeutic application. It is widely used as a positive control in genotoxicity testing (OECD guidelines 471, 473, 474) and as a model carcinogen in chemoprevention studies. It is also a reference standard for environmental monitoring of nitrosamine contamination in food, water, and cosmetics. Due to its high potency, it is strictly regulated and not for human or veterinary use.

C4H8N2O2

116.12

116.058

59-89-2

N-Nitrosomorpholine-d4;61578-30-1;N-Nitrosomorpholine-d8;1219805-76-1

6046

Yellow crystals

1.3±0.1 g/cm3

226.1±15.0 °C at 760 mmHg

84 °F (NTP, 1992) ; 29 °C ; 84 °F ; 29 °C

90.5±20.4 °C

0.1±0.4 mmHg at 25°C

1.547

-0.55

0

4

0

8

80.1

0

O1C([H])([H])C([H])([H])N(C([H])([H])C1([H])[H])N=O

ZKXDGKXYMTYWTB-UHFFFAOYSA-N

InChI=1S/C4H8N2O2/c7-5-6-1-3-8-4-2-6/h1-4H2

4-nitrosomorpholine

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: 100 mg/mL (861.18 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (21.53 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 25.0 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: ≥ 2.5 mg/mL (21.53 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 25.0 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: ≥ 2.5 mg/mL (21.53 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 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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