共查询到20条相似文献,搜索用时 15 毫秒
1.
P. Aravind M.N.V. Prasad P. Malec A. Waloszek K. Strzałka 《Journal of trace elements in medicine and biology》2009,23(1):50-60
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. 相似文献
2.
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. 相似文献
3.
M. García-Tomás J. Sánchez M. Piles M.T. Mitjavila 《Animal reproduction science》2010,117(3-4):314-321
Oxidative stress plays a key role in the male reproductive function. Differences between rabbit breeds have been found for testis size, seminiferous tubule diameter, number and size of interstitial and germ cells, etc. Traits related to the redox system could also be affected by genetic factors. It is likely that differences between breeds for these traits would lead to differences in reproductive maturation and fertility.We have investigated in the present paper the age-related changes of the plasma testosterone (TST) concentration, superoxide anion (O2?) radical formation, superoxide dismutase (SOD) activity, catalase (CAT) activity and thiobarbituric acid-reactive substances (TBARs) level in testis of rabbits in two breeds selected for different aptitudes (Caldes for growth rate and Prat for litter size). The effect of birth season for these traits was also assessed.Major changes in parameters related to oxidative stress were observed at an early age and most probably can be explained by the concomitant changes in testicular structure and function. Both lines showed similar developmental profiles and levels for all the variables studied. There was no interaction between line and birth season, consequently environmental conditions affected both lines in the same manner. Significant differences between males born in different seasons were found for O2? (4.84 ± 0.19 RLU/mg tissue min versus 5.67 ± 0.19 RLU/mg tissue min), SOD (6.12 ± 0.11 U/mg protein versus 7.09 ± 0.11 U/mg protein) and CAT (0.058 ± 0.002 K/mg protein versus 0.040 ± 0.002 K/mg protein). Future studies should take into account differences between seasons for a more precise analysis. 相似文献
4.
《Saudi Journal of Biological Sciences》2017,24(6):1370-1374
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. 相似文献
5.
Binhua Zhou Baojian Li Wei Yi Xianzhang Bu Lin Ma 《Bioorganic & medicinal chemistry letters》2013,23(13):3759-3763
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. 相似文献
6.
Yinshi Sun Haifang Zhu Jianhua Wang Zhengbo Liu Jianjie Bi 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2009,877(8-9):733-737
Water-soluble salvianolic acid A (Sal A) and salvianolic acid B (Sal B) were successfully isolated and purified from the crude extract of Salvia miltiorrhiza by high-speed counter-current chromatography (HSCCC). The solvent system was n-hexane–ethyl acetate–methanol–water (3:6:6:10, v/v/v/v). 4.27 mg of Sal A and 32.09 mg of Sal B were obtained from 260 mg of the crude sample. The purities of Sal A and Sal B were 96.67% and 97.43%, respectively. Their structures were identified by 1H NMR and 13C NMR. Antioxidant activities of Sal A and Sal B were also evaluated and compared by the methods of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) radical cation decolourisation assay. Both Sal A and Sal B showed high radical scavenging activities with their EC50 values being 1.43 ± 0.09 and 1.81 ± 0.01 μg/ml in DPPH radical method. The ABTS results showed that Sal A and Sal B exhibited high total antioxidant activities, their EC50 values were 1.35 ± 0.00 and 1.43 ± 0.01 μg/ml, respectively. 相似文献
7.
Georgia Tanou Athanassios Molassiotis Grigorios Diamantidis 《Environmental and Experimental Botany》2009,65(2-3):270-281
The effect of salinity (200 mM NaCl, 7 d) on cellular oxidative metabolism and necrotic lesion formation were analyzed in strawberry (Fragaria × ananassa Duch., cv. Selva) leaves. It was found that NaCl-induced oxidative stress in strawberry leaves, as evidence by an H2O2/O2? accumulation, an increase in lipid peroxidation and carbonyl-groups content. Salinity visible symptoms, H2O2/O2? generation and cell death lesions formation co-occurred mainly in the rim of the leaf surface. However, DNA laddering was not evident in the leaves exposed to salinity. Leaf extracts from plants exposed to NaCl were able to reduce Fe3+ but not to chelate Fe2+, as judged by their promoting effect on deoxy-d-ribose oxidation system. Also, NaCl-treated leaf extracts were ineffective at protecting against plasmid DNA strand breakage induced by OH in a Fenton-type system. NaCl caused an accumulation in putrescine and spermidine, an oxidation of ascorbate and glutathione redox pairs and an inhibition in the activities of some ROS-metabolizing enzymes (e.g., catalase, ascorbate peroxidase, glutathione reductase). Experiments employing pharmacological agents suggested that NaCl-induced production of H2O2 was likely linked to NAD(P)H-oxidase and amine oxidase regulation and was signalled by nitric oxide (NO), salicylic acid (SA), protein kinase and Ca2+ channel activity. Further, a conceptual model for the action of NaCl-driven oxidative stress on necrotic death-like destruction is proposed. 相似文献
8.
《Saudi Journal of Biological Sciences》2017,24(1):103-107
Exposures to particulate matter with a diameter of 2.5 μm or less (PM2.5) may influence the risk of birth defects and make you allergic, which causes serious harm to human health. Bamboo charcoal can adsorb harmful substances,that was of benefitto people’s health. In order to figure out the optimal adsorbtion condition and the intrinsic change of bamboo charcoal, five chemicals were adsorbed by bamboo charcoal and were analyzed by FT-IR. The optimal blast time was 80 min of Na2SO3, 100 min of Na2S2O8, 20 min of Na2SO4, 120 min of Fe2(SO4)3 and 60 min or 100 min of S. FT-IR spectra showed that bamboo charcoal had five characteristic peaks of SS stretch, H2O stretch, OH stretch, CO stretch or CC stretch, and NO2 stretch at 3850 cm−1, 3740 cm−1, 3430 cm−1, 1630 cm−1 and 1530 cm−1, respectively. For Na2SO3, the peaks at 3850 cm−1, 3740 cm−1, 3430 cm−1, 1630 cm−1 and 1530 cm−1 achieved the maximum at 20 min. For Na2S2O8, the peaks at 3850 cm−1, 3740 cm−1, 3430 cm−1 and 1530 cm−1 achieved the maximum at 40 min. For Na2SO4, the peaks at 3850 cm−1, 3740 cm−1 and 1530 cm−1 achieved the maximum at 40 min. For Fe2(SO4)3, the peaks at 3850 cm−1, 3740 cm−1, 1630 cm−1 and 1530 cm−1 achieved the maximum at 120 min. For S, the peaks at 3850 cm−1 and 3740 cm−1 achieved the maximum at 40 min, the peaks at 1630 cm−1 and 1530 cm−1 achieved the maximum at 40 min. It proved that bamboo charcoal could remove sulfur powder from air to restrain sulfur allergies. 相似文献
9.
《Saudi Journal of Biological Sciences》2017,24(6):1355-1360
Sulfur and ammonia nitrogen are rich nutrient pollutants, after entering water can cause algal blooms, cause eutrophication of water body, the spread of them will not only pollute the environment, destroy the ecological balance, but also harm human health through food chain channels, especially drinking-water toxicosis. Acticarbon can adsorb harmful substances, it was beneficial for people’s health. In order to figure out the optimal adsorption condition and the intrinsic change of acticarbon, five chemicals were adsorbed by acticarbon and analyzed by FT-IR. The optimal adsorption condition of Fe2(SO4)3, Na2SO4, Na2S2O8, S and Na2SO3 was 9 g/1000 g at 80 min, 21 g/1000 g at 20 min, 15g/1000 g at 20 min, 21 g/1000 g at 60 min and 21 g/1000 g at 100 min, respectively. FT-IR spectra showed that acticarbon had eight characteristic peaks, such as S-S stretch, H2O stretch, OH stretch, CH stretch, CO or CC stretch, CH2 bend, CH were at 3850 cm−1, 3740 cm−1, 3435 cm−1, 2925 cm−1, 1630 cm−1, 1390 cm−1, 1115 cm−1, 600 cm−1, respectively. For FT-IR spectra of Fe2(SO4)3, the peaks at 3850 cm−1, 3740 cm−1, 2925 cm−1 achieved the maximum with 9 g/1000 g at 20 min. For Na2SO4, the peaks at 2925 cm−1, 1630 cm−1, 1390 cm−1, 1115 cm−1, 600 cm−1 achieved the maximum with 21 g/1000 g at 120 min. For ones of Na2S2O8, the peaks at 3850 cm−1, 3740 cm−1, 1390 cm−1, 1115 cm−1, 600 cm−1, achieved the maximum with 2 g/1000 g at 80 min. For ones of S, the peaks at 3850 cm−1, 3740 cm−1, 2925 cm−1 achieved the maximum with 19 g/1000 g at 100 min, the peaks at 1390 cm−1, 1115 cm−1, 600 cm−1 achieved the maximum with 19 g/1000 g at 20 min. For FT-IR spectra of Na2SO3, the peaks at 1630 cm−1, 1390 cm−1, 1115 cm−1, 600 cm−1 achieved the maximum with 2 g/1000 g at 100 min. It provided that acticarbon could adsorb and desulphurize from sulfur solution against drinking-water toxicosis. 相似文献
10.
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. 相似文献
11.
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. 相似文献
12.
To further understand the physiological mechanisms of cold-tolerance in banana plants, the responses of four introducing cultivars (cv.) W811 (via long-term cold adaptation), PB, BJ10 and BJ11 to low-temperature stress (LT) were investigated. LT caused increased malondialdehyde (MDA) content, elevated contents of hydrogen peroxide (H2O2) and superoxide radical (O2−), and decreased photochemical efficiency (Fv/Fm) and net photosynthetic rate (Pn) in the leaves of four banana cultivars, but cv. W811 showed better LT tolerance than the other three cultivars. After 72 h of LT, four key antioxidative enzymes in the four cultivars showed different responses. Compared to controls, superoxide dismutase (SOD) activities in the four cultivars showed a significant decrease and W811 had the smallest amount of decrease. Catalase (CAT) activities showed a significant decrease. Peroxidase (POD) activities kept relatively higher activities and showed no significant changes (P > 0.05) in W811, BJ10 and BJ11 whereas that in PB showed a significant increase (P < 0.001). Ascorbate peroxidase (APX) activities in W811 and PB showed no significant changes (P > 0.05). Our results showed that higher cold-tolerance in cv. W811 may correlate with the long-term cold adaptation of the antioxidative enzymes such as SOD, POD and APX that alleviate oxidative stress caused by LT. 相似文献
13.
14.
David F. Stowe Ashish K. Gadicherla Yifan Zhou Mohammed Aldakkak Qunli Cheng Wai-Meng Kwok Ming Tao Jiang James S. Heisner MeiYing Yang Amadou K.S. Camara 《生物化学与生物物理学报:生物膜》2013,1828(2):427-442
We tested if small conductance, Ca2 +‐sensitive K+ channels (SKCa) precondition hearts against ischemia reperfusion (IR) injury by improving mitochondrial (m) bioenergetics, if O2‐derived free radicals are required to initiate protection via SKCa channels, and, importantly, if SKCa channels are present in cardiac cell inner mitochondrial membrane (IMM). NADH and FAD, superoxide (O2?), and m[Ca2 +] were measured in guinea pig isolated hearts by fluorescence spectrophotometry. SKCa and IKCa channel opener DCEBIO (DCEB) was given for 10 min and ended 20 min before IR. Either TBAP, a dismutator of O2?, NS8593, an antagonist of SKCa isoforms, or other KCa and KATP channel antagonists, were given before DCEB and before ischemia. DCEB treatment resulted in a 2-fold increase in LV pressure on reperfusion and a 2.5 fold decrease in infarct size vs. non-treated hearts associated with reduced O2? and m[Ca2 +], and more normalized NADH and FAD during IR. Only NS8593 and TBAP antagonized protection by DCEB. Localization of SKCa channels to mitochondria and IMM was evidenced by a) identification of purified mSKCa protein by Western blotting, immuno-histochemical staining, confocal microscopy, and immuno-gold electron microscopy, b) 2-D gel electrophoresis and mass spectroscopy of IMM protein, c) [Ca2 +]‐dependence of mSKCa channels in planar lipid bilayers, and d) matrix K+ influx induced by DCEB and blocked by SKCa antagonist UCL1684. This study shows that 1) SKCa channels are located and functional in IMM, 2) mSKCa channel opening by DCEB leads to protection that is O2? dependent, and 3) protection by DCEB is evident beginning during ischemia. 相似文献
15.
In this study, a series of novel bromophenols were synthesized from benzoic acids and methoxylated bromophenols. The synthesized compounds were evaluated by using different bioanalytical antioxidant assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS+) radical scavenging assays. Also, reducing power of novel bromophenols were evaluated by Cu2+-Cu+ reducing, Fe3+-Fe2+ reducing and [Fe3+-(TPTZ)2]3+-[Fe2+-(TPTZ)2]2+ reducing and ferrous ions (Fe2+) chelating abilities. The compounds demonstrate powerful antioxidant activities when compared to standard antioxidant molecules of α-tocopherol, trolox, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT). Also in the last part of this studies novel bromophenols were tested against some metabolic enzymes including acetylcholinesterase (AChE), butyrylcholinesterase (BChE) enzymes and carbonic anhydrase I, and II (hCA I and hCA II) isoenzymes. The newly synthesized bromophenols showed Ki values in a range of 6.78 ± 0.68 to 126.07 ± 35.6 nM against hCA I, 4.32 ± 0.23 to 72.25 ± 12.94 nM against hCA II, 4.60 ± 1.15 to 38.13 ± 5.91 nM against AChE and 7.36 ± 1.31 to 29.38 ± 3.68 nM against BChE. 相似文献
16.
Two novel prenylated phenols, cyclocomunoindenol (1) and cyclocomunohexanol (2) were isolated from the cortex of roots of Artocarpus communis. Their structures were determined by spectroscopic methods. Compounds 2 and 6 revealed significant DPPH-scavenging activity with an IC50 values of 435.48 ± 0.93 and 53.55 ± 8.73 μM, respectively. Compounds 1, 2, and 6 displayed significant ABTS+ scavenging activity with an IC50 values of 164.26 ± 2.44, 227.01 ± 3.64, and 44.09 ± 0.88 μM, respectively. Compound 6 exhibited an inhibitory effect on XO activity with an IC50 value of 10.91 ± 1.77 μM and the relative oxygen radical absorbance capacity (ORAC) values of 1–6, using ORAC-pyrogallol red (PGR) assay, were determined to be 0.28 ± 0.06, 0.31 ± 0.02, 0.55 ± 0.25, 0.84 ± 0.36, 0.35 ± 0.15, and 0.70 ± 0.09, respectively. Antioxidants 5 and 6 significantly attenuate UVA radiation-induced damage on human HaCaT keratinocytes and Hs68 fibroblasts. These finding showed that 1–6 may be used as antioxidants and 5 and 6 may protect skin against the adverse effects of UV radiation. 相似文献
17.
Chronic lead exposure induces hypertension affecting endothelial function. We investigated whether low-concentration lead exposure alters blood pressure and vascular reactivity, focusing on the roles of NO, oxidative stress, cyclooxygenase-derived vasoconstrictor prostanoids, and the local angiotensin–renin system. Aortic rings from 3-month-old Wistar rats were treated daily with lead acetate (first dose 4 mg/100 g, subsequent doses 0.05 mg/100 g, im) or vehicle for 30 days. Treatment increased lead blood levels (12 μg/dl), blood pressure, and aortic ring contractile response to phenylephrine (1 nM–100 mM). Contractile response after L-NAME administration increased in both groups but was higher after lead treatment. Lead effects on Rmax decreased more after apocynin and superoxide dismutase administration compared to control. Indomethacin reduced phenylephrine response more after lead treatment than in controls. The selective COX-2 inhibitor NS398, thromboxane A2/prostaglandin H2 receptor antagonist SQ 29,548, TXA2 synthase inhibitor furegrelate, EP1 receptor antagonist SC 19220, and ACE inhibitor and AT1 receptor antagonist losartan reduced phenylephrine responses only in vessels from lead-treated rats. Basal and stimulated NO release was reduced and local O2− liberation increased in the lead-treated group compared to controls. eNOS, iNOS, and AT1 receptor protein expression increased with lead exposure, but COX-2 protein expression decreased. This is the first demonstration that blood Pb2+ (12 µg/dl) concentrations below the WHO-established values increased systolic blood pressure and vascular phenylephrine reactivity. This effect was associated with reduced NO bioavailability, increased reactive oxygen species production, increased participation of COX-derived contractile prostanoids, and increased renin–angiotensin system activity. 相似文献
18.
Although quinones represent a class of organic compounds that may exert toxic effects both in vitro and in vivo, the molecular mechanisms involved in quinone species toxicity are still largely unknown, especially in the presence of transition metals, which may both induce the transformation of the various quinone species and result in generation of harmful reactive oxygen species. In this study, the oxidation of 1,4-naphthohydroquinone (NH2Q) in the absence and presence of nanomolar concentrations of Cu(II) in 10 mM NaCl solution over a pH range of 6.5–7.5 has been investigated, with detailed kinetic models developed to describe the predominant mechanisms operative in these systems. In the absence of copper, the apparent oxidation rate of NH2Q increased with increasing pH and initial NH2Q concentration, with concomitant oxygen consumption and peroxide generation. The doubly dissociated species, NQ2−, has been shown to be the reactive species with regard to the one-electron oxidation by O2 and comproportionation with the quinone species, both generating the semiquinone radical (NSQ−). The oxidation of NSQ− by O2 is shown to be the most important pathway for superoxide (O2−) generation with a high intrinsic rate constant of 1.0×108 M−1 s−1. Both NSQ− and O2− served as chain-propagating species in the autoxidation of NH2Q. Cu(II) is capable of catalyzing the oxidation of NH2Q in the presence of O2 with the oxidation also accelerated by increasing the pH. Both the uncharged (NH2Q0) and the mono-anionic (NHQ−) species were found to be the kinetically active forms, reducing Cu(II) with an intrinsic rate constant of 4.0×104 and 1.2×107 M−1 s−1, respectively. The presence of O2 facilitated the catalytic role of Cu(II) by rapidly regenerating Cu(II) via continuous oxidation of Cu(I) and also by efficient removal of NSQ− resulting in the generation of O2−. The half-cell reduction potentials of various redox couples at neutral pH indicated good agreement between thermodynamic and kinetic considerations for various key reactions involved, further validating the proposed mechanisms involved in both the autoxidation and the copper-catalyzed oxidation of NH2Q in circumneutral pH solutions. 相似文献
19.
Tomasz Korzeniak Corine Mathonière Abdellah Kaiba Philippe Guionneau Marcin Koziel Barbara Sieklucka 《Inorganica chimica acta》2008,361(12-13):3500-3504
Ionic triads formed by [NiII(bipy)3]2+ (bipy = 2,2′-bipyridyl) and diamagnetic [MIV(CN)8]4? (M = Mo and W) were prepared and structurally characterized. The two compounds are isostructural and their structure consists of a three-dimensional hydrogen-bonded framework where cation–anion interactions occur through short contacts M–CN?H–C(bipy). Before irradiation, the Mo analogue behaves as paramagnet with small intermolecular interactions between the [NiII(bipy)3]2+ cations. Upon irradiation with visible light, it exhibits a reversible photomagnetic effect, which is interpreted in terms of the formation of paramagnetic [MoV(CN)8]3? and [NiII(bipy)2(bipy?)]+ due to the outer-sphere electron transfer. 相似文献
20.
Boerhaavia diffusa Linn. of family Nyctaginaceae is a known traditional medicinal plant and has been used in the treatment of many free radical mediated diseases. Excessive formation of free radicals, either reactive oxygen species (ROS) or reactive nitrogen species (RNS) is responsible for damaging various biomolecules like DNA, lipids and proteins. The present investigation was initially carried out to explore the possible link between antioxidant, oxidative DNA damage protective and α-amylase inhibitory property of B. diffusa root extract and their bioactive fraction. Our results illustrated an enhanced DPPH radical scavenging activity/antioxidant power of methanol root extract (IC50 < 250 μg/ml) than ethanol (IC50 = 250 μg/ml) and aqueous extract (IC50 > 250 μg/ml). In addition, the methanol root extract also showed better oxidative DNA damage protective activity and α-amylase inhibitory property than ethanol and aqueous root extract. Phytochemical screening of B. diffusa ethanol and methanol root extract showed the presence of saponins, alkaloids, flavonoids, glycosides and terpenoids in large amount. By means of repetitive preparatory TLC and HPLC the potent antioxidant and α-amylase inhibitory fraction was isolated from methanol root extract. Our results illustrated that DPPH radical scavenging activity (IC50 < 250 μg/ml) and oxidative DNA damage protective and α-amylase inhibitory activity of the isolated/purified bioactive compound from methanol extract were significantly closer to that of crude extract, which in turn confirm that antioxidant and antidiabetic property of methanol root extract resides in this fraction and established a significant correlation between antioxidant and inhibitory α-amylase property of this bioactive fraction compound. These profound effects of B. diffusa methanol root extract and its purified fraction against oxidative plasmid DNA damage, antioxidant and α-amylase inhibitory activity may explain its extensive use in daily life and possible health benefits. 相似文献