Enhancements of enantio and diastereoselectivities in reduction of (Z)-3-halo-4-phenyl-3-buten-2-one mediated by microorganisms in ionic liquid/water biphasic system

Reductions of (Z)-C₆H₅CHCXC(O)CH₃ (X = Cl, Br) mediated by Saccharomyces cerevisiae, Candida albicans, Rhodotorula glutinis, Geotrichum candidum and Micrococcus luteus gave the corresponding halohydrins through consecutive reduction reactions of CC and CO bonds. In general, the reactions performed in the biphasic system water/[(bmim)PF₆] gave better diastereoselectivity and enantioselectivity than in pure water.     

Water-soluble N-carboxymethylchitosan derivatives: Preparation,characteristics and its application

In this work, only N-substituted chitosan derivatives (water-soluble N-carboxymethylchitosan derivatives: N-CMC) with different degrees of substitution were obtained by reaction of a fully deacetylated chitosan (derived from deacetylation of chitosan using decrystallized method) with monochloroacetic acid at pH 8 and temperature of 90 °C. The structure of N-carboxymethylchitosan and chitosan was characterized by IR, ¹H, ¹³C and ¹H–¹³C NMR-HSQC spectra. In the IR spectrum of the N-carboxymethylchitosan, the appearance of peak at 1742 cm^?1 was assigned for CO group of NHCH₂COOH of substituted chitosan. In the ¹H NMR spectra, the peaks at about 3.81÷4.06 ppm, assigned for CH₂ groups of NHCH₂ and N(CH₂)₂, were the major feature, while in the ¹H–¹³C NMR-HSQC spectra, signals of CH₂ confirmed the presence of these two different substituted CH₂ groups. The degree of substitution (DS) of N-monosubstitution (DS_N-mono) decreased from 0.47 to 0.03 meanwhile that of N,N-disubstitution (DS_N,N-di) increased from 0.52 to 0.96 since the mass ratio of chitosan/monochloroacetic acid changing from 1/1 to 1/4. The N-carboxymethylchitosan derivatives have been used for adsorption Cu(II) ion from aqueous solution. The results shown that the optimum conditions for adsorption Cu(II) ion in nitrate solution were pH 6.5, temperature of 30 °C, for 60–90 min and the substituted chitosan derivative having DS_N-mono of 0.16 and DS_N,N-di of 0.81 had maximum adsorption capacity of 192 mg Cu(II) per gram of N-CMC.     

Effect of Pb2+ on the production of hydroxyl radical during solid-state fermentation of straw with Phanerochaete chrysosporium

Hydroxyl radical (OH) is a radical species highly destructive for lignin during solid-state fermentation (SSF) of straw with Phanerochaete chrysosporium (Pc). The production of OH at different initial Pb²⁺ concentrations during SSF of straw with Pc was investigated. The results showed that a modest amount (under 200 mg kg⁻¹) of Pb²⁺ could enhance the production of OH, while a higher Pb²⁺ concentration resulted in inhibition. The content of OH reached the peak value at day 12 in the whole tested samples, and the maximal content of OH was obtained at initial Pb²⁺ concentration of 100 mg kg⁻¹. It was also found that the production of OH was connected to enzymatic activity and oxalate content in some degree, in particular, a significant positive correlation was found between oxalate concentration and production of OH.We found that low concentration of Pb²⁺ can promote the degradation of lignin, and the higher initial Pb²⁺ concentration (400 mg kg⁻¹) resulted in inhibition. In addition, it appeared that there was no significant correlation between lignin degradation rate and the production of OH when Pb²⁺ concentration was taken into account.     

Evaluation of 2-indolcarbohydrazones as potent α-glucosidase inhibitors,in silico studies and DFT based stereochemical predictions

2-Indolcarbohydrazones 1–28 were synthesized and evaluated for their α-glucosidase inhibitory potential. A varying degree of inhibitory potential with IC₅₀ values in the range of 2.3 ± 0.11–226.4 ± 6.8 μM was observed while comparing these outcomes with the standard acarbose (IC₅₀ = 906.0 ± 6.3 μM). The stereochemistry of ten (10) randomly selected compounds (1, 3, 6, 8, 12, 18, 19, 23, 25 and 28) was predicted by Density Functional Theory (DFT). The stability of E isomer was deduced by comparing the calculated and experimental vibration modes of ν_CO, ν_NC and ν_CH (CH in NCH-R). It was observed that except compound 18, all other compounds were deduced to have E configuration while molecular modeling studies revealed the key interactions between enzyme and synthesized compounds.     

Free radical scavenging activity from different extracts of leaves of Bauhinia vahlii Wight & Arn.

The objectives of this study were to determine phenolic content and antioxidant activities of chloroform, acetone, methanol and hot water extracts of Bauhinia vahlii leaves. The hot water extract afforded the highest yield (6.3%) while the lowest yield was obtained from the chloroform extract (2.1%). The methanol extract contains higher levels of total phenolics (48.7 ± 0.7 g GAE/100 g extract), tannins (21.7 ± 0.7 g GAE/100 g extract) and flavonoids (10.3 ± 0.2 RE/100 g extract). The extracts were subjected to assess their antioxidant potential using various in vitro systems such as DPPH, ABTS⁺, FRAP, OH, β-carotene linoleic acid bleaching system, phosphomolybdenum reduction and Fe²⁺ chelation. It is concluded that the methanolic extract of B. vahlii leaves have strong antioxidant potential. Further study is necessary for isolation and characterization of the active antioxidants, which may serve as a potential source of natural antioxidants.     

Differential roles of nitric oxide synthases in regulation of ultraviolet B light-induced apoptosis

Ultraviolet B light (UVB) activates nitric oxide synthase(s) (NOSs) and nitric oxide (NO) production, which plays a role in regulation of apoptosis. However, the role of NO in UVB-induced apoptosis remains controversial. In this study, we analyzed expression and activation of constitutive NOSs (cNOSs) and their roles in UV-induced apoptosis of HaCaT keratinocytes. Our data showed that the expression of neuronal NOS (nNOS) was increased while endothelial NOS (eNOS) was uncoupled in the early phase (0–6 h) post-UVB. The expression of both cNOSs peaked at 12 h post-UVB and NO was transiently elevated with 30 min and then steadily rose from 6 to 18 h post-UVB. The expression of iNOS was detected at 6 h post-UVB and then sturdily increased. Inhibition of cNOSs with l-NAME reduced the inducibility of NO in the early and late phases of irradiation. Along with the eNOS uncoupling, an increased level of peroxynitrite (ONOO^?) was detected in the early phase, but not in the late phase post-UVB. Inhibition of cNOSs reduced the production of ONOO^? in the early time, but led to an increase of ONOO^? in the late time after UVB-irradiation. The results indicate that cNOSs regulate NO/ONOO^? imbalance after UVB-irradiation. Our data suggested that the activation of cNOSs in the early phase post-UVB leads to NO/ONOO^? imbalance and promotes apoptosis via a caspase 3-independent pathway. The elevation of NO in the late phase of UVB-irradiation is mainly produced by inducible NOS (iNOS). However, cNOSs also contribute to the NO production and to maintain a higher NO/ONOO^? ratio, which reduces caspase 3 activity and protects cells from UVB-induced apoptosis.     

Calibration of nitric oxide flux generation from diazeniumdiolate NO donors

The 1-(secondary amino) diazen-1-ium-1,2-diolates (NONOates) are the most commonly utilized nitric oxide (NO, nitrogen monoxide) donor because of the ability of different NONOates to spontaneously break down liberating NO at different rates, which can be utilized to control NO fluxes. However, the parameters that determine these fluxes of NO generation, half-lives and stoichiometry of NO per donor, can vary significantly with specific experimental conditions in addition to the donor chosen. Here we report straightforward methods that can be used to determine these parameters. For donors of intermediate half-life (10–80 min) a real-time oxymyoglobin (oxyMb) assay can be analyzed to simultaneously determine both the half-life and the total amount of NO liberated, from which the NO flux can be obtained for any given donor concentration. The half-lives obtained by oxyMb assay are very similar to those obtained by following NONOate decomposition kinetics spectrophotometrically, and a survey of several NONOates from different commercial sources show consistent results. These data provide validation for the methodologies employed. In addition, procedures are described for calibration of donors with shorter (<10 min) and longer (>80 min) half-lives. These procedures can be used to reproducibly and routinely calibrate NO fluxes for a variety of donors under any specific condition.     

Zinc protects Ceratophyllum demersum L. (free-floating hydrophyte) against reactive oxygen species induced by cadmium

Evidence for Zn protection against Cd-induced reactive oxygen species in the free-floating hydrophyte Ceratophyllum demersum L. is presented in this paper. Metal treatments of 10 μmol/L Cd, 10 Cd μmol/L supplemented with Zn (10, 50, 100 and 200 μmol/L) and Zn-alone treatments of the same concentrations were used. Using 5,5 dimethyl pyrroline-N-oxide as the spin-probe, electron spin resonance spectra indicated a drastic increase in hydroxyl radicals (OH) in Cd-10 μmol/L treatments, which was closely correlating with the enhanced formation of hydrogen peroxide (H₂O₂) and generation of superoxide radical (O₂^?) triggered by the oxidation of NADPH. The supplementation of adding Zn (10–200 μmol/L) to the Cd-10 μmol/L treatments significantly decreased the production of free radicals especially by eliminating the precursors of OH through inhibition of NADPH oxidation. Cd-enhanced ROS production which substantially increased the oxidative products of proteins measured as carbonyls was effectively inhibited by Zn supplementation.     

Synthesis of new mer,trans-rhodium(III) hydrido-bis(acetylide) complexes: Structure of mer,trans-[(PMe3)3Rh(CC–C6H4-4-NMe2)2H]

Terminal alkynes (R–CC–H, R = 1-naphthyl, 9-anthryl, 4-Me₂N–C₆H₄–, or the longer analogue, 4-(4-Me₂N–C₆H₄–CC–)–C₆H₄–) react with [Rh(PMe₃)₄Me] at ambient temperature, with loss of methane and one PMe₃ ligand, to form the corresponding mer,trans-[(PMe₃)₃Rh(CCR)₂H] compounds in excellent yield. In this preliminary study, the synthesis and spectroscopic characterization of the four new compounds are reported, along with the single-crystal structure of the R = 4-Me₂N–C₆H₄ derivative.     

Characteristics of activated carbon remove sulfur particles against smog

Sulfur particles, which could cause diseases, were the main powder of smog. And activated carbon had the very adsorption characteristics. Therefore, five sulfur particles were adsorbed by activated carbon and were analyzed by FT-IR. The optimal adsorption time were 120 min of Na₂SO₃, 120 min of Na₂S₂O₈, 120 min of Na₂SO₄, 120 min of Fe₂(SO₄)₃ and 120 min of S. FT-IR spectra showed that activated carbon had the eight characteristic absorption of SS stretch, H₂O stretch, OH stretch, CH stretch, conjugated CO stretch or CC stretch, CH₂ bend, CO stretch and acetylenic CH bend vibrations at 3850 cm^–1, 3740 cm^–1, 3430 cm^–1, 2920 cm^–1, 1630 cm^–1, 1390 cm^–1, 1110 cm^–1 and 600 cm^–1, respectively. For Na₂SO₃, the peaks at 2920 cm^–1, 1630 cm^–1, 1390 cm^–1 and 1110 cm^–1 achieved the maximum at 20 min. For Na₂S₂O₈, the peaks at 3850 cm^–1, 3740 cm^–1 and 2920 cm^–1 achieved the maximum at 60 min. The peaks at 1390 cm^–1, 1110 cm^–1 and 600 cm^–1 achieved the maximum at 40 min. For Na₂SO₄, the peaks at 3430 cm^–1, 2920 cm^–1, 1630 cm^–1, 1390 cm^–1, 1110 cm^–1 and 600 cm^–1 achieved the maximum at 60 min. For Fe₂(SO₄)₃, the peaks at 1390 cm^–1, 1110 cm^–1 and 600 cm^–1 achieved the maximum at 20 min. For S, the peaks at 1630 cm^–1, 1390 cm^–1 and 600 cm^–1 achieved the maximum at 120 min. It provided that activated carbon could remove sulfur particles from smog air to restrain many anaphylactic diseases.     

Synthesis,antioxidant, and antimicrobial evaluation of some 2-arylbenzimidazole derivatives

A series of 2-arylbenzimidazole derivatives (3a–3p and 4a–4i) were synthesized and evaluated as potential antioxidant and antimicrobial agents. Their antioxidant properties were evaluated by various in vitro assays including hydroxyl radical (HO) scavenging, superoxide radical anion (O₂^?) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, and ferric reducing antioxidant power. Results demonstrated that compounds with hydroxyl group at the 5-position of benzimidazole ring had a comparable or better antioxidant activity in comparison to standard antioxidant tert-butylhydroquinone (TBHQ). Markedly, compound 4h that showed the highest HO scavenging activity (EC₅₀ = 46 μM) in vitro had a significant reduction of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced intracellular oxidative stress and H₂O₂-induced cell death. In addition, these compounds showed moderate to good inhibitory activity against Staphylococcus aureus selectively at noncytotoxic concentrations.     

The kinetics of the reaction of nitrogen dioxide with iron(II)- and iron(III) cytochrome c

The reactions of NO₂ with both oxidized and reduced cytochrome c at pH 7.2 and 7.4, respectively, and with N-acetyltyrosine amide and N-acetyltryptophan amide at pH 7.3 were studied by pulse radiolysis at 23 °C. NO₂ oxidizes N-acetyltyrosine amide and N-acetyltryptophan amide with rate constants of (3.1±0.3)×10⁵ and (1.1±0.1)×10⁶ M⁻¹ s⁻¹, respectively. With iron(III)cytochrome c, the reaction involves only its amino acids, because no changes in the visible spectrum of cytochrome c are observed. The second-order rate constant is (5.8±0.7)×10⁶ M⁻¹ s⁻¹ at pH 7.2. NO₂ oxidizes iron(II)cytochrome c with a second-order rate constant of (6.6±0.5)×10⁷ M⁻¹ s⁻¹ at pH 7.4; formation of iron(III)cytochrome c is quantitative. Based on these rate constants, we propose that the reaction with iron(II)cytochrome c proceeds via a mechanism in which 90% of NO₂ oxidizes the iron center directly—most probably via reaction at the solvent-accessible heme edge—whereas 10% oxidizes the amino acid residues to the corresponding radicals, which, in turn, oxidize iron(II). Iron(II)cytochrome c is also oxidized by peroxynitrite in the presence of CO₂ to iron(III)cytochrome c, with a yield of ~60% relative to peroxynitrite. Our results indicate that, in vivo, NO₂ will attack preferentially the reduced form of cytochrome c; protein damage is expected to be marginal, the consequence of formation of amino acid radicals on iron(III)cytochrome c.     

Mechanisms and kinetic profiles of superoxide-stimulated nitrosative processes in cells using a diaminofluorescein probe

In this study, we examined the mechanisms and kinetic profiles of intracellular nitrosative processes using diaminofluorescein (DAF-2) as a target in RAW 264.7 cells. The intracellular formation of the fluorescent, nitrosated product diaminofluorescein triazol (DAFT) from both endogenous and exogenous nitric oxide (NO) was prevented by deoxygenation and by cell membrane-permeable superoxide (O₂⁻) scavengers but not by extracellular bovine Cu,Zn-SOD. In addition, the DAFT formation rate decreased in the presence of cell membrane-permeable Mn porphyrins that are known to scavenge peroxynitrite (ONOO⁻) but was enhanced by HCO₃⁻/CO₂. Together, these results indicate that nitrosative processes in RAW 264.7 cells depend on endogenous intracellular O₂⁻ and are stimulated by ONOO⁻/CO₂-derived radical oxidants. The N₂O₃ scavenger sodium azide (NaN₃) only partially attenuated the DAFT formation rate and only with high NO (>120 nM), suggesting that DAFT formation occurs by nitrosation (azide-susceptible DAFT formation) and predominantly by oxidative nitrosylation (azide-resistant DAFT formation). Interestingly, the DAFT formation rate increased linearly with NO concentrations of up to 120–140 nM but thereafter underwent a sharp transition and became insensitive to NO. This behavior indicates the sudden exhaustion of an endogenous cell substrate that reacts rapidly with NO and induces nitrosative processes, consistent with the involvement of intracellular O₂⁻. On the other hand, intracellular DAFT formation stimulated by a fixed flux of xanthine oxidase-derived extracellular O₂⁻ that also occurs by nitrosation and oxidative nitrosylation increased, peaked, and then decreased with increasing NO, as previously observed. Thus, our findings complementarily show that intra- and extracellular O₂⁻-dependent nitrosative processes occurring by the same chemical mechanisms do not necessarily depend on NO concentration and exhibit different unusual kinetic profiles with NO dynamics, depending on the biological compartment in which NO and O₂⁻ interact.     

Organogold(I) complexes of a C2-symmetric diacetylide ligand derived from 1,1′-bi-2-naphthol

Alkynylgold(I) complexes incorporating a chiral binaphthyl group have been prepared. Bis(alkyne) reagents [rac-1,1′-C₂₀H₁₂-2,2′-(OCH₂CCH)₂] (1) and [rac-1,1′-C₂₀H₁₂-2,2′-(OC(O)CH₂CCH)₂] (2), react with [AuCl(SMe₂)] and base to give insoluble oligomeric alkynylgold(I) complexes [rac-1,1′-C₂₀H₁₂-2,2′-(OCH₂CCAu)₂]_n (3) and [rac-1,1′-C₂₀H₁₂-2,2′-(OC(O)CH₂CCAu)₂]_n (4), which react with phosphine or diphosphine ligands to give soluble complexes [rac-1,1′-C₂₀H₁₂-2,2′-(OCH₂CCAuPR₃)₂] (5), R = Ph or Cy, [rac-1,1′-C₂₀H₁₂-2,2′-(OCH₂CCAu)₂(Ph₂P(CH₂)_nPPh₂)] (6), or [rac-1,1′-C₂₀H₁₂-2,2′-(OC(O)CH₂CCAu)₂(Ph₂P(CH₂)_nPPh₂)] (7), with n = 3–5. Several of the complexes 6 and 7 are shown to exist as mixtures of isomeric forms in solution.     

Iron deprivation-induced reactive oxygen species generation leads to non-autolytic PCD in Brassica napus leaves

Using iron-deprived (–Fe) chlorotic as well as green iron-deficient (5 μM Fe) and iron-sufficient supplied (50 μM Fe) leaves of young hydroponically reared Brassica napus plants, we explored iron deficiency effects on triggering programmed cell death (PCD) phenomena. Iron deficiency increased superoxide anion but decreased hydroxyl radical (OH) formation (TBARS levels). Impaired photosystem II efficiency led to hydrogen peroxide accumulation in chloroplasts; NADPH oxidase activity, however, remained on the same level in all treatments. Non-autolytic PCD was observed especially in the chlorotic leaf of iron-deprived plants, to a lesser extent in iron-deficient plants. It correlated with higher DNAse-, alkaline protease- and caspase-3-like activities, DNA fragmentation and chromatin condensation, hydrogen peroxide accumulation and higher superoxide dismutase activity. A significant decrease in catalase activity together with rising levels of dehydroascorbic acid indicated a strong disturbance of the redox homeostasis, which, however, was not caused by OH formation in concordance with the fact that iron is required to catalyse the Fenton reaction leading to OH generation. This study documents the chain of events that contributes to the development of non-autolytic PCD in advanced stages of iron deficiency in B. napus leaves.     

Scavenging and antioxidant activities of immunomodulating polysaccharides isolated from Salvia officinalis L.

Crude polysaccharides, isolated from the aerial parts of sage (Salvia officinalis L.) by sequential extraction with water (A), hot ammonium oxalate (B), dimethyl sulfoxide (C), 1 M (D) and 4 M (E) potassium hydroxide solutions, and six ion-exchange fractions of A were examined for their ability to inhibit peroxidation of liposome lipid by hydroxyl radicals and to reduced DPPH radical content. The highest inhibition of liposome lipid peroxidation was found with crude polysaccharides A, B and D, antioxidant activities reached ～37%. The purified fractions A1 and A2 inhibited the liposome peroxidation to ～35%. However, the radical scavenging abilities of the most active crude polysaccharides A, B and C on DPPH radicals were found in the range 80–90%, while the most active purified fractions A₃–A₆ in three or fourfold doses achieved 75–92%. The least effective tested polysaccharides succeeded 20% inhibition using both methods.     

Mechanistic and kinetic evaluation of biosorption of reactive azo dyes by free,immobilized and chemically treated Citrus sinensis waste biomass

Sorption potential of Citrus sinensis biomass for reactive yellow 42 and reactive red 45 was investigated with variation of pH, biosorbent dose and dye concentration. Biosorbent was treated by organic and inorganic reagents of which acetic acid and acetonitrile enhanced the sorption capacities for reactive yellow 42 and reactive red 45, respectively. Sorption equilibrium was established within 60 min using free and chemically treated biosorbent, while prolonged to 120 min using immobilized biosorbent. Freundlich isotherm and pseudo-second-order rate law described best the sorption mechanism. FT-IR analysis of biosorbent revealed the presence of CO, CO, NH and OH groups on the surface of biosorbent. Desorption experiments were performed to regenerate the sorbent, making the process more economical and environment friendly.     

Mitochondria generated nitric oxide protects against permeability transition via formation of membrane protein S-nitrosothiols

Mitochondria generated nitric oxide (NO) regulates several cell functions including energy metabolism, cell cycling, and cell death. Here we report that the NO synthase inhibitors (L-NAME, L-NNA and L-NMMA) administered either in vitro or in vivo induce Ca²⁺-dependent mitochondrial permeability transition (MPT) in rat liver mitochondria via a mechanism independent on changes in the energy state of the organelle. MPT was determined by the occurrence of cyclosporin A sensitive mitochondrial membrane potential disruption followed by mitochondrial swelling and Ca²⁺ release. In in vitro experiments, the effect of NOS inhibitors was dose-dependent (1 to 50 µM). In addition to cyclosporin A, L-NAME-induced MPT was sensitive to Mg²⁺ plus ATP, EGTA, and to a lower degree, to catalase and dithiothreitol. In contrast to L-NAME, its isomer D-NAME did not induce MPT. L-NAME-induced MPT was associated with a significant decrease in both the rate of NO generation and the content of mitochondrial S-nitrosothiol. Acute and chronic in vivo treatment with L-NAME also promoted MPT and decreased the content of mitochondrial S-nitrosothiol. SNAP (a NO donor) prevented L-NAME mediated MPT and reversed the decrease in the rate of NO generation and in the content of S-nitrosothiol. We propose that S-nitrosylation of critical membrane protein thiols by NO protects against MPT.     

Novel rhodium complexes containing a bulky iminophosphine ligand and their use as catalysts for the hydroboration of vinylarenes

Addition of o-Ph₂PC₆H₄CHN-2,6-ⁱPr₂C₆H₃ (1) to [RhCl(coe)₂]₂ (coe = cis-cycloctene) gave several new iminophosphino rhodium(I) complexes including [Rh(κ²-o-Ph₂PC₆H₄CHN-2,6-ⁱPr₂C₆H₃)(μ-Cl)]₂ (2). Addition of 1 to Rh(acac)(coe)₂ (acac = acetylacetonato) gave [Rh(acac)(κ²-o-Ph₂PC₆H₄CHN-2,6-ⁱPr₂C₆H₃)] (3) in yields of up to 75%. Complex 3 has been examined for its ability to catalyze the hydroboration of a series of vinyl arenes. Reactions using catecholborane and pinacolborane seem to proceed largely through a dehydrogenative borylation mechanism to give a number of boronated products.     

Nitroxyl (HNO) suppresses vascular Nox2 oxidase activity

Nox2 oxidase activity underlies the oxidative stress and vascular dysfunction associated with several vascular-related diseases. We have reported that nitric oxide (NO) decreases reactive oxygen species production by endothelial Nox2. This study tested the hypothesis that nitroxyl (HNO), the redox sibling of NO, also suppresses vascular Nox2 oxidase activity. Specifically, we examined the influence of two well-characterized HNO donors, Angeli’s salt and isopropylamine NONOate (IPA/NO), on Nox2-dependent responses to angiotensin II (reactive oxygen species production and vasoconstriction) in mouse cerebral arteries. Angiotensin II (0.1 μmol/L)-stimulated superoxide (measured by lucigenin-enhanced chemiluminescence) and hydrogen peroxide (Amplex red fluorescence) levels in cerebral arteries (pooled basilar and middle cerebral (MCA)) from wild-type (WT) mice were ~60% lower (P<0.05) in the presence of either Angeli’s salt (1 μmol/L) or IPA/NO (1 μmol/L). Similarly, phorbyl 12,13-dibutyrate (10 μmol/L; Nox2 activator)-stimulated hydrogen peroxide levels were ~40% lower in the presence of IPA/NO (1 μmol/L; P<0.05). The ability of IPA/NO to decrease superoxide levels was reversible and abolished by the HNO scavenger l-cysteine (3 mmol/L; P<0.05), but was unaffected by hydroxocobalamin (100 μmol/L; NO scavenger), ODQ (10 μmol/L; soluble guanylyl cyclase (sGC) inhibitor), or Rp-8-pCPT-cGMPS (10 μmol/L; cyclic guanosine monophosphate (cGMP)-dependent protein kinase inhibitor). Angiotensin II-stimulated superoxide was substantially less in arteries from Nox2-deficient (Nox2^−/y) versus WT mice (P<0.05). In contrast to WT, IPA/NO (1 μmol/L) had no effect on superoxide levels in arteries from Nox2^−/y mice. Finally, angiotensin II (1–1000 μmol/L)-induced constriction of WT MCA was virtually abolished by IPA/NO (1 μmol/L), whereas constrictor responses to either the thromboxane A₂ mimetic U46619 (1–100 nmol/L) or high potassium (122.7 mmol/L) were unaffected. In conclusion, HNO suppresses vascular Nox2 oxidase activity via a sGC–cGMP-independent pathway. Thus, HNO donors might be useful therapeutic agents to limit and/or prevent Nox2-dependent vascular dysfunction.