Prevention of peroxynitrite-induced oxidation and nitration reactions by ellagic acid

Four benzoic acid derivatives and three phenylpropanoids were tested for their ability to suppress oxidation of dichlorodihydrofluorescein (DCDHF) induced by 3-morpholinosydnonimine (SIN-1, a peroxynitrite donor). Ellagic acid was found to potently inhibit this oxidation and to inhibit oxidation of DCDHF induced by peroxynitrite itself. Moreover, this compound prevented peroxynitrite-induced oxidative single strand breaks in pTZ 18U plasmid DNA and nitration of tyrosyl residues in bovine serum albumin. These results show that ellagic acid protects biomolecules against oxidative and nitrative damage induced by peroxynitrite in vitro.     

一种新的产生和检测过氧亚硝基的化学发光体系

研究产生和消除过氧亚硝基（Peroxynitrite anion,ONOO^-）是自由基生物学和医学的一项紧迫任务。为此,建立了一种新的产生和检测ONOO^-的化学发光体系,并评估了检测的最佳条件。该方法为：10mmol／L羟胺与0．5mol,LNaOH、1mmol／L、乙二胺四乙酸二钠（Disodium ethylenediamine tetraacetate,EDTA）反应产生ONOO^-,随后用MnO2粉末过滤反应液以除去H2O2,然后在测量管内加入100μL抗氧化剂和860μL0．Imol／L的碳酸盐缓冲液（pH10）,再加入40μL过滤后的ONOO^-反应液、混匀、延迟10s,测10s化学发光强度。以抗氧化剂茶多酚、抗坏血酸、芦丁和黄芩苷作清除ONOO^-的实验。结果表明,本体系是一种灵敏价廉、可靠易行的筛选ONOO^-清除剂的新方法。     

Bicarbonate Effect in the Ozone-UV Process in the Presence of Nitrate

Ozonation and advanced oxidation processes (AOP) are very efficient methods for the destruction of refractory organic matters. These virtues have always been related to the production of hydroxyl radicals HO^?, which are extremely powerful and non-selective oxidants. In this study, the O₃-UV process is used as an AOP, where hydroxyl radicals are generated from the photodecomposition of ozone by short wavelength ultraviolet radiation. The obtained results indicated a weak scavenging effect of tert-butanol proving that hydroxyl radicals and ozone are not the only oxidants existing in the medium. Moreover, bicarbonate, known for a long time as effective HO^? radical scavengers, does not slow down the oxidation of benzoic acid, but surprisingly increases it. Chlorides significantly decrease the degradation of organic compounds through their reaction with HO^? radicals to produce chlorine. Carbonate radicals, nitrate and nitrogenated species as peroxynitrite/?peroxynitrous acid are involved in the oxidative mechanisms.     

Comparison of Peroxynitrite-Scavenging Capacities of Several Citrus Fruit Peels

Citrus fruit peels contain a large variety of bioactive components and are considered as potential sources of functional components. The purpose of this study was to evaluate the peroxynitrite-scavenging activities of different citrus fruit peels. The peroxynitrite-scavenging activities of methanolic extracts of nine dried citrus fruit peels were evaluated as determined by their ability to attenuate the peroxynitrite-mediated nitrotyrosine formation in albumin. The results showed that all of the tested citrus fruit peels had the ability to attenuate the formation of nitrotyrosine. The total phenolics contents highly correlated with the peroxynitrite-scavenging activities. The results also indicated that the peroxynitrite-scavenging activity of citrus fruit peels was mainly attributed to the total phenolics.     

Evaluation of peroxynitrite-scavenging capacities of several commonly used fresh spices

Peroxynitrite-induced nitration of protein tyrosine residues is considered as one of the major pathological causes of several human diseases, e.g. cardiovascular disorders. Therefore, it appears that attenuation of peroxynitrite-induced nitration by certain foods could be beneficial to human health. Certain spices, used widely in folk medicine for cardiovascular disorders, conceivably protect against the activities of peroxynitrite. Seven culinary spices, including chilli, garlic, ginger, leek, onion, shallot and Welsh onion, were selected for this study. The peroxynitrite-scavenging capacities of these aqueous spice extracts were evaluated on the basis of their ability to attenuate peroxynitrite-induced nitrotyrosine formation in albumin. All of the spices had abilities to attenuate the peroxynitrite-mediated protein nitration. Ginger had outstanding peroxynitrite-scavenging ability. The phenolics and flavonoids in certain spices had abilities to suppress the peroxynitrite-mediated tyrosine nitration reaction. This indicates that these compounds could act as peroxynitrite-scavengers.     

Comprehensive evaluation of antioxidant activity for various substances with 5-axe cobweb chart

Antioxidant activities of various substances against peroxynitrite and peroxyl radical generated from 2,2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH) were evaluated by the previously proposed method [Terashima, M., Nakatani, I., Harima, A., Nakamura, S., & Shiiba M. (2007). New method to evaluate water-soluble antioxidant activity based on protein structure change. Journal of Agricultural and Food Chemistry, 55(1), 165–169] using myoglobin as a probe. Activities of several antioxidants against five different reactive oxygen species, DPPH, hypochlorite ion, hydroxyl radical, peroxynitrite, and peroxyl radical, were characterised comprehensively by 5-axe cobweb charts. For example, Trolox, ascorbic acid, and ferulic acid show similar activities against DPPH radicals (7–10 mM VC), the shapes of the 5-axe cobweb charts are different from each others. This clear-cut expression would be useful to predict probable physiological effects of various antioxidants and to compare quality of antioxidants contained in food materials and food products.     

Scavenging effects of lotus seed extracts on reactive nitrogen species

The inhibitory effect of lotus (Nelumbo nicifera) seed extracts extracted with water (LSWE), ethyl acetate (LSEAE) and hexane (LSHE) on reactive nitrogen species, induced by DNA damage in macrophage RAW 264.7 cells, was investigated. The results showed that all extracts could inhibit nitric oxide accumulation in LPS-activated RAW 264.7 cells. The extracts in the range of 0.01–0.2 mg/ml showed a dose-dependent inhibitory effect on the accumulation of nitric oxide upon decomposition of sodium nitroprusside (SNP). The potency of inhibitory activity was in the order: LSEAE > LSWE > LSHE. The results of the comet assay indicated that the three extracts could inhibit DNA damage in macrophage RAW 264.7 cells induced by SNP. In addition, the three samples, at 0.2 mg/ml, showed 63%, 59%, and 38% inhibition of DNA damage in macrophage RAW 264.7 cells induced by peroxynitrite, respectively. All extracts tested were found to be potent peroxynitrite scavengers, capable of preventing the nitration of tyrosine. The data obtained suggest that lotus seed extracts might act as chemopreventers through reduction of excess amounts of nitric oxide.     

Inhibition of reactive nitrogen species invitro and exvivo by thioredoxin h2 from sweet potato ‘Tainong 57’ storage roots

In this study, the ability of thioredoxin h2 (TRX h2) expressed in Escherichia coli to scavenge ON and ONOO⁻ were investigated. The data obtained show that TRX h2 generated a dose-dependent inhibition on production of nitrite and superoxide radicals. TRX h2 also caused a dose-dependent inhibition of the oxidation of dihydrorhodamine 123 (DHR) by peroxynitrite. Spectrophotometric analyses revealed that TRX h2 suppressed the formation of ONOO⁻-mediated tyrosine nitration through an electron donation mechanism. In further studies, TRX h2 also showed a significant ability of inhibiting the nitration of bovine serum albumin (BSA) in a dose-dependent manner. In vivo TRX h2 inhibited LPS-induced nitrite production in macrophage in a concentration-dependent manner. The present study suggested that TRX h2 had an efficient reactive nitrogen species scavenging ability. TRX h2 might be a potential effective NO and ONOO⁻ scavenger useful for the prevention of the NO and ONOO⁻ involved diseases.     

Carbonate-catalyzed chemiluminescence decomposition of peroxynitrite via (CO2)2 intermediate

Peroxynitrous acid (ONOOH) was formed by the on-line rapid reaction of acidified hydrogen peroxide with nitrite in a simple flow system. A weak chemiluminescent (CL) signal was observed due to the production of singlet oxygen (¹O₂) when ONOOH reacted with NaOH, whereas the replacement of NaOH by Na₂CO₃ markedly enhanced the CL intensity. The predominant CL-enhanced pathway was achieved by the carbonate-catalyzed decomposition of peroxynitrite (ONOO⁻). Carbonate species was regenerated in the process, that is, carbonate acts as a catalyst. Based on the studies of CL and fluorescence spectra, a possible CL mechanism from the reaction of carbonate with ONOOH was proposed. In brief, ONOOH was an unstable compound in acidic solution and could be quenched into ONOO⁻ in basic media. It was suggested that ONOO⁻ reaction with excess HCO₃⁻ proceeded via one-electron transfer to yield bicarbonate ion radicals (HCO₃√). The recombination of HCO₃√ may directly generate excited triplet dimers of two CO₂ molecules [(CO₂)₂^*]. With the decomposition of this unstable intermediate to CO₂, the energy was released by CL emission. The addition of uranine into carbonate solution caused enhancement of the CL signal, which was due to a part of excited triplet dimers of two CO₂ molecules energy to transfer to uranine, resulting in two CL peaks.