Nitric oxide organic donors

Importantly, the purple color is completely restored upon recooling the solution. Thus, the thermal electron-transfer equilibrium depicted in equation (35) is completely reversible over multiple cooling/warming cycles. On the other hand, the isolation of the pure cation-radical salt in quantitative yield is readily achieved by in vacuo removal of the gaseous nitric oxide and precipitation of the MA+ BF4 salt with diethyl ether. This methodology has been employed for the isolation of a variety of organic cation radicals from aromatic, olefinic and heteroatom-centered donors.174 However, competitive donor/acceptor complexation complicates the isolation process in some cases.175... 

These compounds contain the fragment R as an alkyl or aryl moiety. In other words, they result from the esterification of an alcohol or a phenol with nitrous acid, nitric acid, phosphoric acid, sulfuric acid, or sulfamic acid, respectively. Many of the esters to be examined in this chapter must be activated prior to eliciting their effects, e.g., the organic nitrites and nitrates, which act as donors of nitric oxide or an analogous molecule, and phosphates, which are activated by hydrolysis or even by phosphorylation (antiviral agents). Sulfates are very seldom active or used as prodrugs, but they have significance as metabolites and as industrial xenobiotics. 

Figure 8.2 Proposed mode of action of the organic nitrates, nitroglycerin and nitroprusside. Note that nitroprusside acts as a direct donor of nitric oxide (NO), whereas the nitrates require the presence of nitrosothiols to produce NO.

Nitric oxide generation from L-arginine and nitric oxide donors and the formation of cGMP. L-NMMA inhibits nitric oxide synthase. Some of the nitric oxide donors such as furoxans and organic nitrates and nitrites require a thiol cofactor such as cysteine or glutathione to form nitric oxide. 

Organic nitrites (amyl nitrite and isobutyl nitrite) cause dizziness, giddiness, rapid heart rate, lowered blood pressure, "speeding," and flushing of the skin. These effects last only a few minutes and can readily be repeated. The main effect of the drug on sexual performance is probably to enhance or prolong erection through the release of nitric oxide in the corpora cavernosa (see Chapter 19 Nitric Oxide, Donors, Inhibitors). 

Nitrification must be followed by denitrification to remove nitrogen from wastewater. It implies the reduction of nitrate to nitric oxide, nitrous oxide and nitrogen gas, coupled to the respiratory electron transport chain (because nitrates or nitrites are used as electron acceptors for the oxidation of a variety of organic or inorganic electron donors). 

Two of the patients with a response to nitric oxide gas that precluded transplantation of the heart alone died one, following combined heart lung transplantation, and one, of an intercurrent pneumonia while awaiting suitable donor organs. The pulmonary histology confirmed severe and irreversible pulmonary vascular changes in both patients. 

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