Search results for "nitration"

Protein Tyrosine Nitration Induced by Heme/Hydrogen Peroxide: Inhibitory Effect of Hydroxycinnamoyl Conjugates

2006

The present study was designed to optimize the experimental conditions that govern the heme-catalyzed nitration of protein tyrosine residues by nitrite, and, within this framework, to study the effects of 3,5-dicaffeoylquinic acid and its methyl ester, both of which have been previously reported to be antioxidants and inhibitors of leukocyte functions. Although the presence of hydrogen peroxide is essential in cell-free systems, an excess of this compound was found to be detrimental, so much so that an increase in hemin concentration actually resulted in an inverse effect on the reaction, depending on the levels of fixed hydrogen peroxide. Unlike previous reports on nitrite-induced albumin …

Post-translational modifications of hsp60 and its extracellular release via exosomes are induced by the histone deacetylase inhibitor (HDACi) SAHA in…

2015

The chaperonin Hsp60 has multiple functions, among which that of supporting the growth of some type of tumours (1). HDACi (histone-deacetylase inhibitors) are drugs that regulate gene expression via modulation of epigenetic mechanisms, and induce tumor-cell death (2). Here, we show that in the tumor cells H292 the HDACi SAHA decreases the intracellular level of Hps60 and promotes its extracellular trafficking by exosomal vesicles. SAHA caused a time- and dose-dependent decrease in cell viability with a G/2M cell-cycle arrest at 24 h and cell death at 48 h. These effects were accompanied by production of reactive oxygen species and mitochondrial membrane-potential dissipation. The marked dec…

Modulation of protein tyrosine nitration and inflammatory mediators by isoprenylhydroquinone glucoside.

2007

The nitration of tyrosine caused by peroxynitrite and other reactive nitrogen species is clearly detrimental for some physiological processes; however, its signalling role is still open to controversy. Among the natural phenolics known for their ability to oppose free tyrosine nitration, isoprenylhydroquinone glucoside is investigated due to its unusual structure, which contains a simple hydroxybenzene alkylated by a hemiterpenoid moiety. This hydroquinone was shown to be an effective inhibitor of peroxynitrite-induced protein tyrosine nitration in 3T3 fibroblasts. When tested on bovine seroalbumin nitration, however, the potency was reduced by half and the effect was almost abolished in th…

Interaction of dicaffeoylquinic derivatives with peroxynitrite and other reactive nitrogen species.

2008

Plant phenolic antioxidants, among them catechins and hydroxycinnamoyl conjugates, constitute a well defined class of inhibitors of reactive nitrogen species (RNS). To gain deeper insight in this field, we examined the effects of 3,5-di-O-caffeoylquinic acid (DCA), its methyl ester (DCE) and epigallocatechin gallate (EGCG) in nitrative and oxidative processes. These compounds were found to be strong inhibitors of the nitration of tyrosine residues induced by ONOO- in bovine seroalbumin, with their IC50 values (10-40 microM) notably decreasing in the presence of bicarbonate. When studied on the intracellular protein tyrosine nitration induced by ONOO- in cultured murine fibroblasts as well a…

Understanding the Mechanism of Nitrobenzene Nitration with Nitronium Ion: A Molecular Electron Density Theory Study

2019

Polycondensed nitrogen heterocycles. Part17. Isoxazolo[4,3-d]pyrazolo[3,4-f][1,2,3]triazepine. A new ring system

1987

The title compounds were prepared by nitration of compounds 2, reduction of the dinitro derivatives 4 and diazotization of the diamino derivatives 6 followed by an intramolecular coupling reaction. Compound 4a showed good activity against Salmonella cholerasuis and Clostridium perfringens bacteria.

Die darstellung nitrierter phenolischer mehrkernverbindungen durch kondensation von nitrophenol und seinen derivaten

1970

Es wurden einige Mehrkernverbindungen dargestellt, die aus Nitrophenoleinheiten bestehen, welche in ortho-Stellung zur phenolischen OH-Gruppe uber Methylengruppen verbunden sind. Die Nitrierung fertiger phenolischer Mehrkernverbindungen ist hierzu nicht geeignet. Jedoch gelingt die Darstellung durch Kondensation von Nitrophenolen mit Formaldehyd oder durch Kondensation von chlormethylierten Nitrophenolen mit anderen Nitrophenolen. Im ersten Fall ist die Bildung des Benzdioxanringes als Nebenreaktion zu beobachten. All dargestellten Mehrkernverbindungen wurden dunnschichtchromatographisch auf Reinheit gepruft; ihre Struktur wurde in beinahe allen Fallen durch voneinander unabhangige. Synthes…

Effects of plant alkylphenols on cytokine production, tyrosine nitration and inflammatory damage in the efferent phase of contact hypersensitivity

2007

Background and purpose: The phenolic compounds isoprenylhydroquinone glucoside (IHG), 3,5-dicaffeoylquinic acid (DCA), and its methyl ester (DCE) have previously been shown to inhibit both contact hypersensitivity (CHS) and peroxynitrite reactivity. The present work seeks to establish a relationship between the anti-inflammatory effect and the release of cytokines and tyrosine nitration in skin. Experimental approach: Murine CHS was developed by means of sensitization and challenge with dinitrofluorobenzene (DNFB) or oxazolone. Ear swelling was measured 24 and 96 h after challenge. Interleukin (IL)-1b, IL-4, and tumour necrosis factor (TNF)-a were measured by ELISA; and the expression of in…

Selective Derivatization of Calix[4]arenes via Amino Groups Attached to the Wide Rim

2004

A new strategy is proposed for the synthesis of tetraether derivatives of calix[4]arenes bearing at the wide rim nitro and phthalimido groups in well defined positions. Since both groups are precursors of amino functions, calix[4]arenes substituted by different N-acylamino residues are easily available in four steps. The essential steps during the synthesis of the precursor consist in the protection of amino groups by the formation of their phthalimides followed by ipso-nitration of the remaining tert-butylphenol ether units. This nitration occurs without side reactions at the phthalimido substituted units, in contrast to simple N-acyl derivatives.

Mechanism of genotoxicity and electron density distribution by NMR of 5-nitro-3-thiophenecarboxamides, a novel group of direct-acting mutagens in Sal…

1993

Abstract The mutagenic activity of 23 5-nitro-3-thiophenecarboxanilides and of 5-nitro-3-thiophenecarboxamide, the prototype, (NTCAs) have been evaluated in the Ames test on Salmonella typhimurium strains TA100 ad TA98 with and without metabolic activation. Effects of different substituents (electron-donating and electron-withdrawing) were studied to evaluate structural features that affect the metabolism and the bacterial mutagenic potency. All the derivatives were direct-acting mutagens, the mutagenic potency ranging from 0.7 to 142 revertants (rev.)/nmol in TA100 and from 0.09 to 68 rev./nmol in TA98 strain. Results obtained with strains TA98NR and TA98/1,8-DNP 6 indicated that the mutag…