naphthoquinones and 2-bromo-1-4-naphthoquinone

Silver nanoparticles have been synthesized by a simple and inexpensive solution combustion method with urea as fuel. The structural and morphology of the silver nanoparticles were investigated through X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersion Spectra (EDS) techniques. Structural and morphological results confirmed the nanocrystalline nature of the silver nanoparticles. Density Functional Theory (DFT) calculations were also performed to study the ground and excited state behavior of 2-bromo-1,4-naphthoquinone (2-BrNQ) and 2-BrNQ on silver nanoparticles. Surface-Enhanced Raman Scattering (SERS) spectra of 2-BrNQ adsorbed on silver nanoparticles were investigated. The CO, CH in-plane bending and CBr stretching modes were enhanced in SERS spectrum with respect to normal Raman spectrum. The spectral analysis reveals that the 2-BrNQ adsorbed 'stand-on' orientation on the silver surface. Density Functional Theory (DFT) calculations are also performed to study the vibrational features of 2-BrNQ molecule and 2-BrNQ molecule on silver surface.

Topics: Adsorption; Metal Nanoparticles; Models, Molecular; Naphthoquinones; Powder Diffraction; Quantum Theory; Silver; Spectrum Analysis, Raman; Surface Properties; X-Ray Diffraction

Apatone™, a combination of menadione (2-methyl-1,4-naphthoquinone, VK3) and ascorbic acid (vitamin C, VC) is a new strategy for cancer treatment. Part of its effect on tumor cells is related to the cellular pro-oxidative imbalance provoked by the generation of hydrogen peroxide (H2O2) through naphthoquinone redox cycling. In this study, we attempted to find new naphthoquinone derivatives that would increase the efficiency of H2O2 production, thereby potentially increasing its efficacy for cancer treatment. The presence of an electron-withdrawing group in the naphthoquinone moiety had a direct effect on the efficiency of H2O2 production. The compound 2-bromo-1,4-naphthoquinone (BrQ), in which the bromine atom substituted the methyl group in VK3, was approximately 10- and 19-fold more efficient than VK3 in terms of oxygen consumption and H2O2 production, respectively. The ratio [H2O2]produced / [naphthoquinone]consumed was 68 ± 11 and 5.8 ± 0.2 (µM/µM) for BrQ and VK3, respectively, indicating a higher efficacy of BrQ as a catalyst for the autoxidation of ascorbic acid. Both VK3 and BrQ reacted with glutathione (GSH), but BrQ was the more effective substrate. Part of GSH was incorporated into the naphthoquinone, producing a nucleophilic substitution product (Q-SG). The depletion of BrQ by GSH did not prevent its redox capacity since Q-SG was also able to catalyze the production of reactive oxygen species. VK3/VC has already been submitted to clinical trials for the treatment of prostate cancer and has demonstrated promising results. However, replacement of VK3 with BrQ will open new lines of investigation regarding this approach to cancer treatment.

Topics: Antineoplastic Agents; Ascorbic Acid; Drug Combinations; Drug Substitution; Humans; Hydrogen Peroxide; Naphthoquinones; Oxidation-Reduction; Oxygen Consumption; Reactive Oxygen Species; Structure-Activity Relationship; Tumor Cells, Cultured; Vitamin K 3

Plasma thiol concentration has long been recognised as a potential indicator for assessing the severity of oxidative stress processes within physiological systems. While such measurements are normally restricted to research studies, this communication has sought to develop and characterise a novel approach through which this parameter could be exploited within routine clinical settings. The protocol is based on the rapid derivatisation of reduced thiol functionalities (protein and monomolecular moieties) through the homogenous reaction of a naphthoquinone bromide derivative. Bromide released in the reaction can be easily quantified through ion chromatography (Isocractic Dionex DX-120 incorporating an IonPac AS14 anion exchange column and a 25 microL sample loop with conductivity detector. Mobile phase consisted sodium carbonate/bicarbonate (3.5 mM/1 mM) at a flow rate of 1.5 mL/min). Method selectivity and sensitivity has been critically evaluated. The technique covers the range 15 microM-3.5 mM PSH with a detection limit of 9 microM PSH and analysis time of 5 min. The efficacy of the approach for the analysis of human plasma from five volunteers was assessed (ranging from 49 to 72 microM with an intra assay variation of less than 5% in all cases). The responses were validated through comparison with the standard Ellman colorimetric technique.

Topics: Adult; Anions; Bromides; Chromatography, Ion Exchange; Humans; Middle Aged; Naphthoquinones; Oxidation-Reduction; Oxidative Stress; Sensitivity and Specificity; Sulfhydryl Compounds