Organic Nitrite Research Articles

Cytochrome P450‐P450 Reductase Mediated Nitric Oxide And Nitrosothiol Generation From Organic Nitrates

Cytochrome P450 reductase (CPR) and cytochrome P450 (CP) play important roles in organic nitrate bioactivation, however, the mechanism by which they convert organic nitrate to nitric oxide (NO) remains unknown. Questions remain regarding the initial precursor of NO that serves to link organic nitrate to the activation of soluble guanylyl cyclase (sGC). To characterize the mechanism of CPP-CP-mediated organic nitrate bioactivation, Electron Paramagnetic Resonance (EPR) spectroscopy, chemiluminescence NO analyzer, NO electrode, and immunoassay studies were performed. With rat hepatic microsomes or purified CPR, the presence of NADPH triggered organic nitrate reduction to nitrite (NO2-). The CPR flavin site inhibitor diphenyleneiodonium inhibited this NO2- generation, while the CP inhibitor clotrimazole did not. However, clotrimazole greatly inhibited NO2--dependent NO generation. Therefore, CPR catalyzes organic nitrate reduction producing nitrite, while CP can mediate further nitrite reduction to NO. Nitrite-dependent NO generation contributed less than 10% of the CPR-CP-mediated NO generation from organic nitrates, thus NO2- is not the main precursor of NO. Studies suggested that organic nitrite (R-O-NO) is produced from organic nitrate reduction by CPR. Further reaction of organic nitrite with thiols leads to NO or nitrosothiol generation and thus stimulates the activation of sGC. Thus, organic nitrite is the initial product in the process of organic nitrate activation and is the precursor of NO and nitrosothiols, serving as the link between organic nitrate and sGC activation.

Mechanisms of mercury removal by O and OH in the atmosphere

The mechanisms of the reactions of gaseous Hg atoms with O3 and OH radical are evaluated from current kinetic and enthalpy data. The reaction, O3+Hg→HgO+O2, is considered to be an unlikely pathway for atmospheric conditions. Considerations given here suggest that the reaction may occur with initial formation of a metastable HgO3 molecule that in laboratory experiments is the source of the HgO product observed to accumulate on the walls of the reactor (HgO3→HgO(s)+O2). Laboratory studies of the gas phase reaction, Hg+OH→HgOH (2), have been reported using relative rate measurements initiated by photodissociation of an organic nitrite in mixtures of Hg vapor with NO, air and various reference hydrocarbons. Computer simulations of this reaction system suggest that the use of reactive reference gases (e.g., cyclohexane) leads to the generation of significant ozone in these NOx–RH–air mixtures, and the resulting O3–Hg reaction can result in an over-estimate of the rate of reaction (2). Also the apparent rate coefficients for reaction (2) are highly dependent on the assumed rate coefficients of its competitive reactions of dissociation in HgOH→Hg+OH (3), and association of HgOH molecule with other free radicals present in the system: HgOH+X→XHgOH (4); X=OH, HO2, RO, RO2, NO, NO2. Reaction (4) competes successfully with HgOH decomposition for the laboratory conditions employed, and the kinetic measurements relate to the rate determining reaction, Hg+OH→HgOH in this case. However, the use of these laboratory measurements of k2 to determine the extent of Hg removal by OH in the troposphere will greatly over-estimate the importance of Hg removal by this reaction.

Xanthine Oxidase Catalyzes Anaerobic Transformation of Organic Nitrates to Nitric Oxide and Nitrosothiols: CHARACTERIZATION OF THIS MECHANISM AND THE LINK BETWEEN ORGANIC NITRATE AND GUANYLYL CYCLASE ACTIVATION

Organic nitrates have been used clinically in the treatment of ischemic heart disease for more than a century. Recently, xanthine oxidase (XO) has been reported to catalyze organic nitrate reduction under anaerobic conditions, but questions remain regarding the initial precursor of nitric oxide (NO) and the link of organic nitrate to the activation of soluble guanylyl cyclase (sGC). To characterize the mechanism of XO-mediated biotransformation of organic nitrate, studies using electron paramagnetic resonance spectroscopy, chemiluminescence NO analyzer, NO electrode, and immunoassay were performed. The XO reducing substrates xanthine, NADH, and 2,3-dihydroxybenz-aldehyde triggered the reduction of organic nitrate to nitrite anion (NO2-). Studies of the pH dependence of nitrite formation indicated that XO-mediated organic nitrate reduction occurred via an acid-catalyzed mechanism. In the absence of thiols or ascorbate, no NO generation was detected from XO-mediated organic nitrate reduction; however, addition of L-cysteine or ascorbate triggered prominent NO generation. Studies suggested that organic nitrite (R-O-NO) is produced from XO-mediated organic nitrate reduction. Further reaction of organic nitrite with thiols or ascorbate leads to the generation of NO or nitrosothiols and thus stimulates the activation of sGC. Only flavin site XO inhibitors such as diphenyleneiodonium inhibited XO-mediated organic nitrate reduction and sGC activation, indicating that organic nitrate reduction occurs at the flavin site. Thus, organic nitrite is the initial product in the process of XO-mediated organic nitrate biotransformation and is the precursor of NO and nitrosothiols, serving as the link between organic nitrate and sGC activation.

Reduction of Organic Nitrites to Nitric Oxide Catalyzed by Xanthine Oxidase: Possible Role in Metabolism of Nitrovasodilators

Xanthine oxidase (XO) was shown to catalyze the reduction of isoamyl and isobutyl nitrites to nitric oxide (NO) in the presence of xanthine under anaerobic conditions. NO was produced at a stoichiometric ratio of 2:1 versus urate generation, steady-state analysis of which showed Michaelis–Menten kinetics with xanthine as varied substrate and substrate inhibition with varied organic nitrite. Under the conditions of NO generation from isoamyl nitrite, XO was progressively inactivated by a mechanism involving conversion of MoS to MoO, yielding “desulfo” enzyme. It is proposed that XO is involved in the metabolism of organic nitrites to NO in vivo and that the observed inactivation serves to explain the phenomenon of tolerance.

IR Investigation of Selective Reduction of NO by Ethene on Cu-ZSM-5

Abstract Adsorbed species during the reaction of selective catalytic reduction of NOx by hydrocarbons (HC-SCR) on Cu ion-exchanged ZSM-5 (Cu-ZSM-5) were investigated by in situ FT-IR using isotopes as well as gas phase analysis. No oxygen-containing species was observed by IR and no reaction proceeded in the presence of gaseous O2 and C2H4 below 473 K, at which HC-SCR occurs. However, an extra NOx species (tentatively assigned to organic nitrite or nitrate species), other than inorganic NOx species derived from O2 and NO, appeared very rapidly in IR at 1670 cm−1 at room temperature, in the presence of adsorbed NO2 species, gaseous C2H4 and NO. Afterwards, a carbonyl species (1677 cm−1) was formed gradually at room temperature. When the extra NOx species was observed, N2 and N2O evolved even at room temperature, therefore, the extra NOx species is considered to be related to HC-SCR. In the O2 + C2H4 + NO reaction at 473 K, no nitrogen-containing species, except for quite a small amount of nitrile (2168 cm−1), was observed in IR. At 473 K, N2, and CO evolved very rapidly with a steep increase in the IR intensity of carboxylate (1574 and 1375 cm−1), while CO2 and carbonyl species increased more slowly.

Impact on Water Quality of High and Low Density Applications of Spent Mushroom Substrate to Agricultural Lands

We studied the influence of spent mushroom substrate (SMS) land application on water resources. Four study sites, including mushroom farms with low or high density land applications of SMS, and two controls, an alfalfa field and a woodland, were instrumented with soilwater lysimeters and groundwater monitoring wells. Water samples were collected during the dormant season (winter) and growing season (spring). Samples were analyzed for a number of water quality parameters, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonia, chloride, nitrate, nitrite, phosphate, sulfate, aluminum, cadmium, calcium, chromium, copper, iron, lead, magnesium, manganese, mercury, nickel, potassium, silicon, sodium, and zinc. Additional analyses were performed for pesticides commonly used in the cultivation of alfalfa or corn, or for insect control, including methomyl, dimethoate, hexazinone, atrazine, diuron and permethrin.All agricultural sites had elevated salt concentrations relative to the wo...

Detection of nitric oxide production from a perfused organ by a luminol-H2O2 system.

Nitric oxide, thought to be the endothelium-derived relaxing factor (EDRF), is involved in intra- and intercellular signalling in various tissues. A system for the continuous detection of NO in the picomolar range from a perfused organ is described. The detection is based upon the chemiluminescence reaction between NO and the luminol (5-amino-2,3-dihydro-1,4-phthalazinedione)-H2O2 system. The chemiluminescence is due to the formation of peroxynitrite from NO and H2O2. The luminol-H2O2 system is specifically reactive to NO, so that other nitrogen-containing compounds, (organic nitrite, organic nitrate, and thio-nitroso compounds) or endothelium-derived compounds do not interfere. The limit of determination was approximately 100 fM. This system has been used to measure continuous NO release from isolated perfused rat kidney and the simultaneous changes of perfusion pressure. In Wistar rats basal NO release was 85 +/- 11 fmol/min-1 (g of kidney weight)-1 (39 pM in the perfusate), and acetylcholine increased NO release dose dependently with a concomitant pressure reduction. The changes in NO release were always associated with mirror image changes in the perfusion pressure. Simple pressure reduction did not interfere with the chemiluminescence. Precise titration data as well as results of some preliminary experiments using this method are presented.

Comparison of isobutyl nitrate and isobutyl nitrite: tolerance and cross-tolerance to glyceryl trinitrate

This study includes the first systematic comparison of an organic nitrate with the corresponding organic nitrite - isobutyl nitrate and isobutyl nitrite. The spasmolytic activity of the nitrite on isolated rabbit aortic strips was stronger, more rapid in onset, but less stable than the activity of the nitrate. In vitro tolerance to glyceryl trinitrate and isobutyl nitrite greatly weakened the activity of isobutyl nitrate, respectively, but had much less effect on isobutyl nitrite. Possible reasons for these differences are discussed.

Lagrangian Model of Nitrogen Kinetics in the Chattahoochee River

A Lagrangian reference frame is used to solve the convection-dispersion equation and interpret water-quality data obtained from the Chattahoochee River. The model was calibrated using unsteady concentrations of organic nitrogen, ammonia, and nitrite plus nitrate obtained during June 1977 and verified using data obtained during August 1976. Reaction kinetics of the cascade type are shown to provide a reasonable description of the nitrogen-species processes in the Chattahoochee River. The conceptual model is easy to visualize in the physical sense and the output includes information that is not easily determined from an Eulerian approach, but which is very helpful in model calibration and data interpretation. For example, the model output allows one to determine which data are of most value in model calibration or verification.

ChemInform Abstract: ATMOSPHERIC PHOTODISSOCIATION LIFETIMES FOR NITROMETHANE, METHYL NITRITE, AND METHYL NITRATE

Chemischer InformationsdienstVolume 11, Issue 36 Preparative Organic Chemistry ChemInform Abstract: ATMOSPHERIC PHOTODISSOCIATION LIFETIMES FOR NITROMETHANE, METHYL NITRITE, AND METHYL NITRATE W. D. TAYLOR, W. D. TAYLORSearch for more papers by this authorT. D. ALLSTON, T. D. ALLSTONSearch for more papers by this authorM. J. MOSCATO, M. J. MOSCATOSearch for more papers by this authorG. B. FAZEKAS, G. B. FAZEKASSearch for more papers by this authorR. KOZLOWSKI, R. KOZLOWSKISearch for more papers by this authorG. A. TAKACS, G. A. TAKACSSearch for more papers by this author W. D. TAYLOR, W. D. TAYLORSearch for more papers by this authorT. D. ALLSTON, T. D. ALLSTONSearch for more papers by this authorM. J. MOSCATO, M. J. MOSCATOSearch for more papers by this authorG. B. FAZEKAS, G. B. FAZEKASSearch for more papers by this authorR. KOZLOWSKI, R. KOZLOWSKISearch for more papers by this authorG. A. TAKACS, G. A. TAKACSSearch for more papers by this author First published: September 9, 1980 https://doi.org/10.1002/chin.198036119Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue36September 9, 1980 RelatedInformation

The determination of iduronic acid and glucuronic acid in heparins by a new technique: Re-evaluation of the variable hexuronic acid composition of mammalian heparins

A new technique for the quantitative determination of the uronic acid components of heparin is described. Heparin was deamination with organic nitrite and methanolyzed. The monomeric derivatives of uronic acids were quantitated by gas chromotography. Depolymerization to monomeric units appeared essentially complete as judged from the yield of uronic acid derivatives. By applying the method the relative contents of iduronic acid and glucuronic acid in a number of heparin samples were estimated. In all samples examined the content of iduronic acid was larger than that of glucuronic acid. A species specific difference in the iduronic acid to glucuronic acid ration of heparin was noted. Noticeable difference of this ratio was observed also between different organs of a species of animal and among heparin fractions obtained from an organ.

Nitroglycerin biotransformation by rat blood serum

The degradation of 14C-labeled glyceryl trinitrate by rat blood serum was investigated. Attention was focused upon the first de-esterification which yielded inorganic nitrite and the two isomeric glyceryl dinitrates. Cleavage of the nitrate group at carbon-2 was favored 4-fold over attack upon each terminal nitrate. The conversion proceeded optimally at approximately pH 7–8 and within the temperature range of 50–57°. Iodoacetamide and p-chloromercuribenzoate inhibited the ability of rat serum to transform nitroglycerin. Serum activity was not lost by dialysis. The data are interpreted as indicating that the de-esterification of nitroglycerin by serum is enzymatic and involves the reduction of organic nitrate to organic nitrite followed by the hydrolysis of nitrite ester to inorganic nitrite. The V max of the unpurified rat serum showed it to be more potent than the hog liver organic nitrate reductase described previously. Unlike the hog liver enzyme, the serum reductase does not require reduced glutathione. Lacking this requirement, the serum system is also free of dependence upon TPNH for the function of glutathione reductase.

Some recent developments in the preparative photolysis of organic nitrites

I N T R O D U C T I O N THE use of photochemical reactions in preparative organic chemistry I has increased considerably during the last twenty years. Many structures accessible only with difficulty by more conventional means have been made available by the agency of radiant energy. One of the most common primary photochemical processes is the homolytic dissociation of an appropriate bond to give rise to two fragments each containing an unpaired electron. The subsequent fate of these free radicals determines the synthetic usefulness of such photochemical processes. It would appear that the nitrogen-oxygen bond in organic nitrite esters is particularly susceptible to homolysis. The latter process does not necessarily have to result f rom photochemical activation: on the contrary, most of the literature on the decomposition of nitrites describes pyrolytic procedures. In the present review, however, special emphasis will be given to photolysis, since the fragments thereby produced are endowed with sufficient energy z to result in subsequent behavior not otherwise attainable. In fact, a very recent development in the field is the photolytic decomposition of nitrites to alkoxy radicals, followed by a stereoselective intramolecular hydrogen abstraction by the latter and recombination of the resulting carbon radicals with NO to form nitrose-monomers, dimers or oximes. This novel course we shall designate the Barton Reaction, in honor of the inventor, and experiments central and peripheral to its nature will form the core of this review.