ascorbic-acid and morpholine

The genotoxicity of endogenously formed N-nitrosamines from secondary amines and sodium nitrite (NaNO(2)) was evaluated in multiple organs of mice, using comet assay. Groups of four male mice were orally given dimethylamine, proline, and morpholine simultaneously with NaNO(2). The stomach, colon, liver, kidney, urinary bladder, lung, brain, and bone marrow were sampled 3 and 24 h after these compounds had been ingested. Although secondary amines and the NaNO(2) tested did not yield DNA damage in any of the organs tested, DNA damage was observed mainly in the liver following simultaneous oral ingestion of these compounds. The administration within a 60 min interval also yielded hepatic DNA damage. It is considered that DNA damage induced in mouse organs with the coexistence of amines and nitrite in the acidic stomach is due to endogenously formed nitrosamines. Ascorbic acid reduced the liver DNA damage induced by morpholine and NaNO(2). Reductions in hepatic genotoxicity of endogenously formed N-nitrosomorpholine by tea polyphenols, such as catechins and theaflavins, and fresh apple, grape, and orange juices were more effective than was by ascorbic acid. In contrast with the antimutagenicity of ascorbic acid in the liver, ascorbic acid yielded stomach DNA damage in the presence of NaNO(2) (in the presence and absence of morpholine). Even if ascorbic acid acts as an antimutagen in the liver, nitric oxide (NO) formed from the reduction of NaNO(2) by ascorbic acid damaged stomach DNA.

Topics: Animals; Ascorbic Acid; Beverages; Comet Assay; DNA Damage; Fruit; Liver; Male; Mice; Morpholines; Muscarinic Antagonists; Mutagenicity Tests; Mutagens; Nitrosamines; Proline; Sodium Nitrite; Tea

High nitrate intake has been shown to result in an increased risk of endogenous formation of N-nitroso compounds. Certain vegetables and vegetable juices contain high concentrations of nitrate. Biological denitrification using strains of Paracoccus denitrificans (P.d.) has been proposed as effective means to reduce nitrate contents in such vegetable juices. During this bacterial denitrification process, substantial nitrite concentrations are transiently formed. This study investigated whether N-nitrosation reactions might occur. The easily nitrosatable amine morpholine was added to red beet juice at high concentration (100 ppm) during denitrification 10 different batches of red beet juice served as raw material. Each batch was submitted to denitrification in the presence and absence of ascorbic acid. In the absence of ascorbic acid, formation of N-nitrosomorpholine (NMOR) was observed in the low ppb range (0.5-8 ppb). Addition of ascorbic acid (500 mg/litre) inhibited the formation of NMOR, except for those instances where the pH was less than 6 and/or nitrate turnover was low (< 200 mg NO3-/litre/hr). Under conditions leading to high rates of nitrate turnover (> 200 mg NO3-/litre/hr), nitrosamine formation can reliably be prevented by ascorbic acid. The results show that bacterial denitrification of red beet juice high in nitrate can be accomplished without the risk of nitrosamine formation.

Topics: Ascorbic Acid; Beverages; Carcinogens; Hydrogen-Ion Concentration; Morpholines; Nitrates; Nitrosamines; Nitrosation; Paracoccus denitrificans; Vegetables

Ascorbate is known to inhibit the acid-catalysed N-nitrosation reactions of nitrite in the normally acid stomach, suggesting a useful therapeutic application of this compound to reduce exposure to the carcinogenic products of such reactions. However, in the achlorhydric stomach, which is particularly predisposed to cancer, increased exposure to endogenous N-nitroso compounds may result from bacterially catalysed reactions. The mechanism of these bacterially mediated reactions is only just beginning to be understood, and, indeed, more than one such mechanism may exist. Despite its usual lack of reactivity towards nitrite at neutral pH, ascorbate proved to be a potent inhibitor of the bacterially mediated (Pseudomonas aeruginosa) nitrosation of morpholine, competing with morpholine for the nitrosating agent elaborated by the bacteria from nitrite (the kinetics of the inhibition were classically competitive). This and other data, particularly with regard to the dependence of the bacterially mediated reaction on amine pKa, are discussed in relation to the potential mechanisms of these bacterially mediated reactions.

Topics: Ascorbic Acid; Bacteria; Kinetics; Morpholines; Nitric Oxide; Nitrites; Nitroso Compounds

It has been suggested that endogenously formed N-nitroso compounds are involved in the aetiology of gastric cancer. In the model of gastric carcinogenesis postulated by Correa, gastric atrophy is an important early stage in the progression to carcinoma which results in the loss of stomach acidity, and colonization of the stomach by bacteria. As a consequence of the metabolic activity of these bacteria intragastric nitrite (a precursor to N-nitroso compounds) and possibly carcinogenic N-nitroso compounds become elevated, which may hasten the progression to carcinoma. Vitamin C has been shown to be an effective inhibitor of acid-catalysed N-nitroso compound formation, in vivo and in vitro, and this has been attributed to its relatively rapid reaction with nitrite in contrast to the slower rates of reaction of nitrite with secondary amines. However, N-nitroso compound formation in the achlorhydric stomach must proceed by mechanisms which operate at neutral pH values. One potential mechanism involves the enzymatic catalysis of N-nitrosation by a subpopulation of the bacteria colonizing the achlorhydric stomach which catalyse these reactions and in particular denitrifying organisms. In this study, we examined the effect of vitamin C on the formation of N-nitrosomorpholine from morpholine and nitrite when mediated by cells of an actively N-nitrosating denitrifying bacterium (Pseudomonas aeruginosa, BM1030) at neutral pH. Despite the fact that vitamin C ordinarily shows little reactivity towards nitrite at neutral pH it did prove to be a potent inhibitor of bacterial N-nitrosamine formation. This study provides some justification for the use of vitamin C as an inhibitor of endogenous N-nitrosation regardless of gastric pH.

Topics: Ascorbic Acid; Hydrogen-Ion Concentration; Morpholines; Nitrites; Nitrosamines; Pseudomonas aeruginosa

Experiments used 409 male CBA mice to study the effect of ascorbic acid on carcinogenesis induced by treatment with such precursors of nitroso compounds as sodium nitrite and morpholine. The former was given with feed in a total dose of 573-891 mg/animal and the latter--with drinking water in a total dose of 138-183 mg/animal. As a result, the total number of tumor-bearers grew from 63.8% (controls) to 82.5%. Treatment with all doses of ascorbic acid tested (1.5; 0.25 and 0.025% with drinking water) was followed by reduction in frequency of tumors in animals treated with nitroso compound precursors to 37.9, 55.1 and 60%, respectively.

Topics: Animals; Ascorbic Acid; Male; Mice; Mice, Inbred CBA; Morpholines; Neoplasms, Experimental; Nitrites; Sodium Nitrite

We determined the effects of phenol and 2,6-dimethoxyphenol (syringol) on N-nitrosomorpholine (NMOR) formation in rats given morpholine and nitrite by gavage. At 30 min post-gavage the recovery (from the stomach, duodenum and blood) of 564 micrograms NMOR was six times higher when administered to rats by gavage with 2 g of semipurified diet (SPD) than when given without food. Rats were gavaged with 12 mg each of morpholine, one of the modifiers and nitrite and examined 30 min later. Syringol decreased the amount of NMOR in both the stomach and blood by 89%, while phenol had no effect. We compared these results with those obtained with ascorbic acid and thiocyanate. The effect of ascorbic acid was similar to that of syringol. However, thiocyanate increased the amount of NMOR in the stomach and blood 2.7- and 4-fold, respectively. When 2 g of SPD was administered to rats by gavage, together with the precursors, syringol and ascorbic acid blocked NMOR formation in the stomach by 58 and 45%, respectively, and thiocyanate enhanced the yield 1.5-fold. The effect of phenol was not significant for the stomach and blood and that of the other modifiers was not significant for blood. Administration of the reactants together with food decreased the NMOR level in blood 155-fold relative to controls (no food), suggesting that food decreased the absorption rate over a 30-min period. These results demonstrate the modifying effect of phenol and syringol on NMOR formation in vivo to be similar to that observed in a previous in vitro study, and show that the effect of food on NMOR levels in blood was more important than that of the modifiers.

Topics: Animals; Ascorbic Acid; Food; Food, Formulated; Gastric Mucosa; Gastrointestinal Contents; Intestinal Absorption; Male; Morpholines; Nitrites; Nitrosamines; Phenol; Phenols; Pyrogallol; Rats; Rats, Inbred Strains; Thiocyanates

Ascorbate anion and glutathione were found to inhibit the aqueous reaction between nitrogen dioxide (NO2) and morpholine (MOR) and thereby prevented the formation of N-nitrosomorpholine (NMOR) and N-nitromorpholine (NTMOR) at both pH 7.4 and 12.5. These antioxidants are approximately 3 orders of magnitude more reactive towards NO2 than is MOR and may play an important role in the prevention of carcinogen formation in the lung due to inhaled NO2. Ammonium sulfamate was ineffective at preventing nitrosation or nitration by NO2 at either pH 7.4 or 12.5.

Topics: Ascorbic Acid; Glutathione; Hydrogen-Ion Concentration; Morpholines; Nitrogen Dioxide; Vitamin E

Topics: Animals; Ascorbic Acid; Citrus; Food Additives; Male; Morpholines; Mutagenicity Tests; Mutation; Rats; Rats, Inbred Strains; Salmonella typhimurium; Sodium Nitrite

The possibility of N-nitrosomorpholine formation was investigated in mice treated with morpholine and then exposed to 45 p.p.m. nitrogen dioxide in an inhalation chamber for 2 h. Following this treatment, the mice were frozen and pulverized in liquid nitrogen and concentrated extracts from the powders of these animals were analyzed for N-nitrosomorpholine using a thermal energy analyzer interfaced to a gas chromatograph. The data indicate that nitrogen dioxide exposure causes the nitrosation of morpholine in vivo. Additional data show that significant levels of artifactually formed N-nitrosomorpholine are found in control animals that are treated with morpholine after exposure to nitrogen dioxide for 2 h unless a combination of L-ascorbic acid and d,1-alpha-tocopherol are used to inhibit nitrosation during the homogenization, extraction, and analysis of the samples. The need for both a lipid phase nitrosation blocker (d,1-alpha-tocopherol) and an aqueous phase nitrosation blocker (L-ascorbic acid) indicates that the nitrosation of morpholine occurs in both a lipid and an aqueous phase in vitro and therefore may occur in both a lipid and an aqueous environment in vivo. The data from this study also demonstrate the importance of adding suitable inhibitors of nitrosation, such as L-ascorbic acid and d,1-alpha-tocopherol to the extraction solution to prevent possible artifactual formation of N-nitrosomorpholine during the extraction and analysis of the samples.

Topics: Animals; Ascorbic Acid; Carcinogens; Kinetics; Male; Mice; Morpholines; Nitrogen Dioxide; Nitrosamines; Vitamin E

Topics: Acetates; Ascorbic Acid; Drug Therapy; Female; Hesperidin; Humans; Ketones; Morpholines; Premenstrual Syndrome; Vitamins