Transformation of ethyl alcohol to ethyl nitrite in acidified saliva: possibility of its occurrence in the stomach

After taking alcoholic beverages, the ethanol is mixed with saliva and then gastric juice. As pH of gastric juice is around 2, the ethanol might be transformed to ethyl nitrite in the stomach by reacting with salivary nitrite. In this study, reactions between ethanol and nitrite in acidified saliva were investigated. The result indicates that nitrite in acidified saliva reacted with ethanol producing ethyl nitrite. It is discussed that ethyl nitrite might be formed in the stomach after drinking alcoholic beverages and that the ethyl nitrite might function as a donor of NO in intestinal and gastric tissues.     

Ethyl nitrite is produced in the human stomach from dietary nitrate and ethanol,releasing nitric oxide at physiological pH: potential impact on gastric motility

Background. Nitric oxide (^∙NO), a ubiquitous molecule involved in a plethora of signaling pathways, is produced from dietary nitrate in the gut through the so-called nitrate–nitrite–NO pathway. In the stomach, nitrite derived from dietary nitrate triggers a network of chemical reactions targeting endogenous and exogenous biomolecules, thereby producing new compounds with physiological activity.Objective. The aim of this study was to ascertain whether compounds with physiological relevance are produced in the stomach upon consumption of nitrate- and ethanol-rich foods.Design. Human volunteers consumed a serving of lettuce (source of nitrate) and alcoholic beverages (source of ethanol). After 15 min, samples of the gastric headspace were collected and ethyl nitrite was identified by GC–MS. Wistar rats were used to study the impact of ethyl nitrite on gastric smooth muscle relaxation at physiological pH.Result. Nitrogen oxides, produced from nitrite in the stomach, induce nitrosation of ethanol from alcoholic beverages in the human stomach yielding ethyl nitrite. Ethyl nitrite, a potent vasodilator, is produced in vivo upon the consumption of lettuce with either red wine or whisky. Moreover, at physiological pH, ethyl nitrite induces gastric smooth muscle relaxation through a cGMP-dependent pathway. Overall, these results suggest that ethyl nitrite is produced in the gastric lumen and releases ^∙NO at physiological pH, which ultimately may have an impact on gastric motility. Systemic effects may also be expected if ethyl nitrite diffuses through the gastric mucosa reaching blood vessels, therefore operating as a ^∙NO carrier throughout the body.Conclusion. These data pinpoint posttranslational modifications as an underappreciated mechanism for the production of novel molecules with physiological impact locally in the gut and highlight the notion that diet may fuel compounds with the potential to modulate gastrointestinal welfare.     

Evaluation of a combined activated carbon prefilter and biotrickling filter system treating variable ethanol and ethyl acetate gaseous emissions

The removal of a 1:1 by weight mixture of ethanol and ethyl acetate was studied in a gas phase biotrickling filter running under conditions that simulated industrial emissions from the flexographic sector, i.e. discontinuous loading (twelve hours per day and five days per week) and oscillating concentration of the inlet stream. Three sets of experimental conditions were tested in which empty‐bed residence time varied from 60 to 25 s (inlet loads from 50 to 90 g C m^?3 h^?1). The biotrickling filter reached a maximum elimination capacity of 48.5 g C m^?3 h^?1 (removal efficiency=68.9%) for an empty‐bed residence time of 40 s. A decrease in the residence time from 40 to 25 s adversely affected the elimination capacity (40.3 g C m^?3 h^?1, removal efficiency=46.6%). For the three tested residence times, outlet concentrations during pollutant feeding were above 100 mg C m^?3 (EU legal limit for flexographic facilities). Then an activated carbon prefilter was installed to buffer the fluctuating concentration, enabling a more stable operation. The desorbed pollutant from the activated carbon during non‐feeding hours also served as an extra source of substrate, avoiding severe starvation. The use of the activated carbon prefilter with a volume 25 times lower than that of the bioreactor was shown to reach an average outlet emission concentration lower than 50 mg C m^?3 operating the biotrickling filter at an empty‐bed residence time of 40 s, with a maximum elimination capacity of 59.6 g C m^?3 h^?1 (removal efficiency=92.0%).     

Reactions of ferrous neuroglobin and cytoglobin with nitrite under anaerobic conditions

Recent evidence suggests that the reaction of nitrite with deoxygenated hemoglobin and myoglobin contributes to the generation of nitric oxide and S-nitrosothiols in vivo under conditions of low oxygen availability. We have investigated whether ferrous neuroglobin and cytoglobin, the two hexacoordinate globins from vertebrates expressed in brain and in a variety of tissues, respectively, also react with nitrite under anaerobic conditions. Using absorption spectroscopy, we find that ferrous neuroglobin and nitrite react with a second-order rate constant similar to that of myoglobin, whereas the ferrous heme of cytoglobin does not react with nitrite. Deconvolution of absorbance spectra shows that, in the course of the reaction of neuroglobin with nitrite, ferric Fe(III) heme is generated in excess of nitrosyl Fe(II)-NO heme as due to the low affinity of ferrous neuroglobin for nitric oxide. By using ferrous myoglobin as scavenger for nitric oxide, we find that nitric oxide dissociates from ferrous neuroglobin much faster than previously appreciated, consistently with the decay of the Fe(II)-NO product during the reaction. Both neuroglobin and cytoglobin are S-nitrosated when reacting with nitrite, with neuroglobin showing higher levels of S-nitrosation. The possible biological significance of the reaction between nitrite and neuroglobin in vivo under brain hypoxia is discussed.     

The interaction of nitrite with photosynthetic electron transport under anaerobic conditions

Chlorella cells were examined in a modulated oxygen polarograph under aerobic and anaerobic conditions. At light intensities below about 600 ergs · cm^?2 · s^?1 of 650 nm light, the oxygen yield and phase lag are lower under anaerobic conditions. Addition of 25 mM sodium nitrite increases both these parameters to values close to those found in the presence of oxygen. It is proposed that nitrite is reduced by Photosystem I thus diverting electrons from the cyclic electron transport pathway. The intersystem electron transport chain becomes more oxidized and this suppresses a backflow of electrons to the oxidizing side of Photosystem II, hence increasing the oxygen yield and the phase lag. The removal of oxygen from the bathing medium also alters the response of dark adapted _Chlorella to a series of saturating light flashes. In terms of the Kok model of Photosystem II (Kok, B., Forbush, B. and McGloin, M. (1970) Photochem. Photobiol. 11, 457–475) there is a large increase in the parameter α. Addition of nitrite reverses this change and virtually restores the response seen in the presence of oxygen. The deactivation of the S₂ state is greatly speeded up in the absence of oxygen but the addition of nitrite again reverses this.     

A novel mutagen, 2-(5-hydroxy-4,6-dinitroindolyl) ethanol, formed in the reaction between 5-hydroxytryptamine and nitrite under acid conditions, especially in the presence of l-cysteine

We examined the mutagenic activity of each of 29 amino acids mixed under acidic conditions with 5-hydroxytryptamine (5-HT) and nitrite using Salmonella typhimurium strain TA 100 with or without a metabolic activation system (S9 mix). The reaction mixture containing l-cysteine was strongly mutagenic without S9 mix. We subjected an ethyl acetate extract of the reaction mixture to HPLC, isolated a mutagenic component, and investigated its chemical structure by LC–mass spectrometry (MS), high-resolution fast atom bombardment (HRFAB)-MS, and ¹H and ¹³C NMR. We identified the mutagen as 2-(5-hydroxy-4,6-dinitro-3-indolyl) ethanol (2HDIE). We injected 8 mg/kg 2HDIE i.p. into male ICR mice and found that the compound increased the frequency of micronuclei in peripheral reticulocytes. Our results suggest that 2HDIE might be formed in vivo by consumption of 5-HT, nitrite and l-cysteine in foods, and might act as a mutagen.     

Functionalization of chitosan by laccase-catalyzed oxidation of ferulic acid and ethyl ferulate under heterogeneous reaction conditions

Chitosan particles were functionalized with ferulic acid (FA) and ethyl ferulate (EF) as substrates using laccase from Myceliophtora thermophyla as biocatalyst. The reactions were performed with chitosan particles under an eco-friendly procedure, in a heterogeneous system at 30 °C, in phosphate buffer (50 mM, pH 7.5).The FA-chitosan derivative presented an intense yellow-orange color stable while the EF-chitosan derivative was colorless. The spectroscopic analyses indicated that the reaction products bound covalently to the free amino groups of chitosan exhibiting a novel absorbance band in the UV/Vis spectra between 300 and 350 nm, at C-2 region by the duplication of C-2 signal in the ¹³C NMR spectrum, via Schiff base bond (NC) exhibiting novel bands in the FT-IR spectrum at 1640 and 1620 cm⁻¹. Additionally, antioxidant capacities of chitosan derivatives showed that the chitosan derivatives presented improved antioxidant properties, especially for FA-chitosan derivative (EC₅₀ were 0.52 ± 0.04, 0.20 ± 0.02 mg/ml for DPPH and ABTS⁺ scavenging, respectively).     

A novel mutagen, 2-(5-hydroxy-4,6-dinitroindolyl) ethanol, formed in the reaction between 5-hydroxytryptamine and nitrite under acid conditions, especially in the presence of L-cysteine

We examined the mutagenic activity of each of 29 amino acids mixed under acidic conditions with 5-hydroxytryptamine (5-HT) and nitrite using Salmonella typhimurium strain TA 100 with or without a metabolic activation system (S9 mix). The reaction mixture containing L-cysteine was strongly mutagenic without S9 mix. We subjected an ethyl acetate extract of the reaction mixture to HPLC, isolated a mutagenic component, and investigated its chemical structure by LC-mass spectrometry (MS), high-resolution fast atom bombardment (HRFAB)-MS, and 1H and 13C NMR. We identified the mutagen as 2-(5-hydroxy-4,6-dinitro-3-indolyl) ethanol (2HDIE). We injected 8 mg/kg 2HDIE i.p. into male ICR mice and found that the compound increased the frequency of micronuclei in peripheral reticulocytes. Our results suggest that 2HDIE might be formed in vivo by consumption of 5-HT, nitrite and L-cysteine in foods, and might act as a mutagen.     

Synthesis of protein,nucleosides and other organic compounds from cyanamide and potassium nitrite under possible primitive earth conditions

The mixing of cyanamide and KNO₂ produced changes from white solids to yellow liquid and then to orange solid. The gases cyanogen and ammonia were formed. No external energy was used. The reactions were carried out with a small amount of O₂. The presence of proteins in the reaction product formed 13 months after the mixing was indicated by the positive reactions of the cyanamide-KNO₂ reaction product with ninhydrin, microbiuret, and Folin reagent; the ultraviolet absorption at about 280 nm; the yield of 24% of 15 amino acids; and molecular weight measurements of more than 160 000. The presence of nucleosides, nucleic acid bases, hydrocarbons, and organic esters in the reaction product formed 2 months after the mixing was indicated by ultraviolet absorption at about 260 nm, and the results of ligand-exchange chromatography, paper chromatography, infrared analysis, mass spectral analysis, and NMR spectroscopy. Possible cyanamide-mediated dehydration reactions and mechanisms are discussed.     

The nitrite reductase gene of Pseudomonas aeruginosa: Effect of growth conditions on the expression and construction of a mutant by gene disruption

Abstract The expression of nitrite reductase has been tested in a wild-type strain of Pseudomonas aeruginosa (Pao1) as a function of nitrate concentration under anaerobic and aerobic conditions. Very low levels of basal expression are shown under non-denitrifying conditions (i.e. absence of nitrate, in both aerobic and anaerobic conditions); anaerobiosis is not required for high levels of enzyme production in the presence of nitrate. A Pseudomonas aeruginosa strain, mutated in the nitrite reductase gene, has been obtained by gene replacement. This mutant, the first of this species described up to now, is unable to grow under anaerobic conditions in the presence of nitrate. The anaerobic growth can be restored by complementation with the wild-type gene.     

烤烟硝酸盐含量与土壤养分的关系

采用多元统计分析方法研究了湖南烤烟叶片硝酸盐、亚硝酸盐含量与土壤养分之间的关系,结果表明：（1）典型相关分析证实烟叶硝酸盐、亚硝酸盐含量与土壤主要含氮养分（土壤全氮、碱解氮、铵态氮）及有机质含量的关系密切,与土壤其他养分含量的相关性较小,反映出在一定范围内,随着土壤含氮养分及有机质含量的增加,烟叶（亚）硝酸盐含量呈现增加的趋势,且土壤含氮养分及有机质含量与烟叶硝酸盐含量关系的密切程度高于与亚硝酸盐含量的相关;（2）根据烟叶硝酸盐、亚硝酸盐含量及其相应的植烟土壤养分（有机质、全氮、碱解氮、铵态氮）含量的大小,通过聚类分析把同一等级的烟叶样品分为高、中、低3类,不同类别相比较,有机质含量越高的土壤,其土壤全氮、碱解氮、铵态氮含量以及相应的烟叶硝酸盐、亚硝酸盐含量也越高,说明土壤有机质的高低,直接影响了土壤氮素的供应状况,进而影响了烟叶硝态氮含量的积累;（3）根据聚类分析结果建立了不同等级烟叶硝酸盐、亚硝酸盐含量高低的判别函数,可作为烟叶硝态氮含量在不同土壤肥力条件下判别归类的参考依据。     

The effect of oxygen on nitrate and nitrite assimilation in leaves of Zea mays L. under dark conditions

The assimilation of nitrate under dark-N₂ and dark-O₂ conditions in Zea mays leaf tissue was investigated using colourimetric and ¹⁵N techniques for the determination of organic and inorganic nitrogen. Studies using ¹⁵N indicated that nitrate was assimilated under dark conditions. However, the rate of nitrate assimilation in the dark was only 28% of the rate under non-saturating light conditions. No nitrite accumulated under dark aerobiosis, even though nitrate reduction occurred under these conditions. The pattern of nitrite accumulation in leaf tissue in response to dark-N₂ conditions consisted of three phases: an initial lag phase, followed by a period of rapid nitrite accumulation and finally a phase during which the rate of nitrite accumulation declined. After a 1-h period of dark-anaerobiosis, both nitrate reduction and nitrite accumulation declined considerably. However, when O₂ was supplied, nitrate reduction was stimulated and the accumulated nitrite was rapidly reduced. Anaerobic conditions stimulated nitrate reduction in leaf tissue after a period of dark-aerobic pretreatment.     

Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions

A combined bioreactor system, composed of a stirred tank and a three-stage tubular bioreactor in series and with a total working volume of 3260 ml, was established. Continuous ethanol production was carried out using Saccharomyces cerevisiae and a very high gravity (VHG) medium containing 280 g l⁻¹ glucose. An average ethanol concentration of 124.6 g l⁻¹ or 15.8% (v) was produced when the bioreactor system was operated at a dilution rate of 0.012 h⁻¹. The yield of ethanol to glucose consumed was calculated to be 0.484 or 94.7% of its theoretical value of 0.511 when ethanol entrapped in the exhaust gas was incorporated. Meanwhile, quasi-steady states and non-steady oscillations were observed for residual glucose, ethanol and biomass concentrations for all of these bioreactors during their operations. Models that can be used to predict yeast cell lysis and viability loss were developed.     

The expression of aquaporins 1 and 9 in adult rat epididymis is perturbed by chronic exposure to ethanol

Aquaporins (AQPs), notably AQP-1 and AQP-9, may contribute to reabsorption of fluid and solute across the epididymis. Ethanol is related to be a toxicant affecting directly or indirectly the epididymis and the sperm motility. This study examined the expression of AQP-1 and AQP-9 in adult epididymis of the UChA and UChB 10% (v/v) ethanol-preferring rats, focusing the ethanol-induced hormonal disturbances upon the regulation of these AQPs. Chronic ethanol intake significantly decreased body weight, while UChA and UChB rats displayed a marked loss of epididymal weights. Both ethanol-consuming animals had a severe reduction of testosterone levels, whereas LH and 17β-estradiol were unchanged. Throughout the epididymis, a strong reaction to AQP-1 was observed in myoid and endothelial cells of the UChB ethanol-preferring rats, differently from a moderate intensity in the initial segment of the UChA rats. In addition, AQP-9 showed a strong immunoreaction in the apical membrane of principal cells at initial segment. In cauda epididymis, the level of AQP-9 was reduced along the microvillus projections in both UChA and UChB rats compared to controls. We conclude that chronic ethanol consumption modulates the androgen levels, thereby modifying the expression pattern of AQP-1 and 9 in the epididymis.     

Reactions of (+)-catechin with salivary nitrite and thiocyanate under conditions simulating the gastric lumen: Production of dinitrosocatechin and its thiocyanate conjugate

Abstract

Catechins are ingested as food components and supplements. It is known that catechins are transformed to dinitrosocatechins by nitrite under acidic conditions, suggesting the possibility of their formation in the stomach because saliva contains nitrite. This paper deals with nitrite-induced transformation of (+)-catechin in methanol extracts of adzuki bean into 6,8-dinitrosocatechin in acidified saliva (pH ≈ 1.9). As the mechanism of its formation, addition of nitric oxide (NO) to (+)-catechin semiquinone radical, both of which were produced in nitrous acid/(+)-catechin systems, was proposed. The dinitrosocatechin was oxidized to the quinone by nitrous acid, and the quinone reacted with a salivary component thiocyanate producing 6′-thiocyanato-6,8-dinitrosocatechin. Since quinones are toxic, we propose a function of thiocyanate as a scavenger of the o-quinone formed from dinitrosocatechins in the stomach.     

The reductive reaction mechanism of tobacco nitrite reductase derived from a combination of crystal structures and ultraviolet-visible microspectroscopy

Assimilatory nitrite reductase (aNiR) reduces nitrite to an ammonium ion and has siroheme and a [Fe(4)S(4)] cluster as prosthetic groups. A reaction mechanism for Nii3, an aNiR from tobacco, is proposed based on high resolution X-ray structures and UV-Vis (ultraviolet-visible) microspectroscopy of Nii3-ligand complexes. Analysis of UV-Vis spectral changes in Nii3 crystals with increasing X-ray exposure showed prosthetic group reductions. In Nii3-NO2(-) structures, X-ray irradiation enhanced the progress of the reduction reaction, and cleavage of the N-O bond was observed when X-ray doses were increased. Crystal structures of Nii3 with other bound ligands, such as Nii3-NO and Nii3-NH(2)OH, were also determined. Further, by combining information from these Nii3 ligand-bound structures, including that of Nii3-NO2(-), with UV-Vis microspectral data obtained using different X-ray doses, a reaction mechanism for aNiR was suggested. Cleavage of the two N-O bonds of nitrite was envisaged as a two-step process: first, the N-O bond close to Lys224 was cleaved, followed by cleavage of the N-O bond close to Arg109. X-ray structures also indicated that aNiR-catalyzed nitrite reduction proceeded without the need for conformation changes in active site residues. Geometrical changes in the ligand molecules and the placement of neighboring water molecules appeared to be important to the stability of the active site residue interactions (Arg109, Arg179, and Lys224) and the ligand molecule. These interactions may contribute to the efficiency of aNiR reduction reactions.     

The hydrogenation and hydroformylation of alkenes as catalyzed by polymer-anchored rhodium trichloride under water gas shift reaction conditions

The ‘heterogenized’ water gas shift catalyst Rh/P4VP, prepared from the reaction of RhCl₃ with poly(4-vinylpyridine), is also active for hydrogenation and hydroformylation of 1-hexene and cyclohexene in aqueous ethoxyethanol under mild shift reaction conditions (typically 0.9 atm. P_CO at 100°C). The catalytic activities for these systems were studied as functions of several experimental variables. Hydroformylation rates increased with the P_CO but exhibited saturation behavior in the 1.5 atm. range. Rates for cyclohexane and hexane production were inhibited by CO at higher pressures. Cyclohexene hydroformylation and hydrogenation turnover frequencies were independent of the polymer-loading (50–150 μM RhCl₃/1.0 g P4VP) indicating that the active species are of the same nuclearity as the principal species present. The temperature dependence did not follow simple Arrhenius behavior, but appeared segmented. These data are discussed in terms of possible mechanisms.     

The effect of plant growth regulators, nitric oxide, nitrate, nitrite and light on the germination of dimorphic seeds of Suaeda salsa under saline conditions

Suaeda salsa, a leaf succulent shrub in the family Chenopodiaceae, is one of the most important halophytes in China. Suaeda salsa produces dimorphic seeds (soft brown seeds and hard black seeds). Seeds of S. salsa were collected from the coastal salt flats near Huanghua City, China. Experiments were conducted to determine the salinity-alleviating effect of plant growth regulators, nitric oxide, nitrate, nitrite and light on the germination of dimorphic seeds of S. salsa. Brown seeds had a higher germination rate than black seeds in all experiments. Black seeds were more sensitive to salt in the absence of light in comparison to brown seeds. Brown seeds absorbed water more quickly in comparison to black seeds and were found to be more tolerant of salt stress. Our results showed that 1-aminocyclopropane-1-carboxylate (ACC, the immediate precursor of ethylene), nitrite, GA₄ and BA improved seed germination in the presence of salt. However, nitrate, GA₁, GA₃ failed to alleviate salt stress. ABA inhibited seed germination and seedling growth. Possible mechanisms involved in the alleviation of salt stress in S. salsa seeds and the ecological adaptation of the seeds to the environment are discussed.