Katarzyna Zawada

1H and 13C NMR‐based sugar profiling with chemometric analysis and antioxidant activity of herbhoneys and honeys

BACKGROUND Herbhoneys, relatively new bee products, are expected to have interesting medicinal properties. However, there is still a lack of data concerning their composition and antioxidant properties. ¹H and ¹³C NMR spectroscopy coupled with chemometric analysis (PCA and PLS-DA) and antioxidant assays (DPPH-ESR and ORAC-FL) were used to study 25 samples of Polish herbhoneys and honeys. RESULTS Antioxidant activity varied among the samples. The best properties were exhibited by cocoa and instant coffee herbhoneys. The contents of total polyphenols and total carotenoids in the studied samples were found to be 70-1340 mg GAE kg⁻¹ and 0-28.05 mg kg⁻¹ respectively. No significant differences between herbhoney and honey samples were found in their sugar profiles. The PCA of ¹³C NMR spectra of the samples in DMSO-d6 resulted in sample clustering due to sucrose content. CONCLUSION Herbhoneys have similar antioxidant properties to traditional honeys, being therefore of equal nutritional value. There was a noticeable influence of the extract concentration on the observed antioxidant effect. For samples with high antioxidant activity, polyphenols were responsible for the observed effect. Sample clustering due to sucrose content in the NMR-PCA study allowed effortless detection of adulteration.

Nitroxide-coated silver nanoparticles: synthesis, surface physicochemistry and antibacterial activity

In this paper, we describe the facile synthesis and physicochemical characteristics of nitroxide-coated silver nanoparticles. The proposed procedure allows us to obtain isolatable, devoid of Ag+ impurities, long-term stable, spherical nanoparticles with an average diameter ca. 7 nm, which exhibit high antibacterial activity towards both Gram-negative and Gram-positive strains. The determined Minimum Bactericidal Concentrations (MBCs) are significantly lower than the values reported for other thiolate-capped silver nanoparticles and range from 4 μg ml−1 (against Pseudomonas aeruginosa) to 12 μg ml−1 (against Staphylococcus aureus). Our studies proved that the nitroxide coverage favours the antibacterial activity of silver nanoparticles, probably due to the ability of nitroxides to be oxidized by reactive oxygen species (ROS) to positively charged oxoammonium ions which can interact strongly with the bacterial membrane. Furthermore, the mechanism of chemisorption of disulphide bisnitroxide on a silver surface has been discussed on the basis of XPS, FTIR and ESR results.

Surface-enhanced Raman spectroscopy studies of phenylpyridines interacting with a copper electrode surface

Surface-enhanced Raman scattering (SERS) spectra serve as a valuable source of information about the organic adsorbates at the surface and about the nature of the oxide films of monolayer thickness. In this study, interactions of 2-phenylpyridine and 3-phenylpyridine with copper surface were investigated by means of SERS spectroscopy and cyclic voltammetry and compared with 4-phenylpyridine. A strong dependence of the spectral pattern on the applied potential was observed for all phenylpyridines. Experimental spectra were compared with ab initio calculations in order to better understand the spectral effects. The SERS results were interpreted in terms of reorientation of the molecular plane with respect to the Cu surface.

Changes in antioxidant capacity of blood due to mutual action of electromagnetic field (1800 MHz) and opioid drug (tramadol) in animal model of persistent inflammatory state.

BACKGROUND The biological effects and health implications of electromagnetic field (EMF) associated with cellular mobile telephones and related wireless systems and devices have become a focus of international scientific interest and world-wide public concern. It has also been proved that EMF influences the production of reactive oxygen species (ROS) in different tissues. METHODS Experiments were performed in healthy rats and in rats with persistent inflammatory state induced by Complete Freunds Adjuvant (CFA) injection, which was given 24 h before EMF exposure and drug application. Rats were injected with CFA or the same volume of paraffin oil into the plantar surface of the left hind paw. Animals were exposed to the far-field range of an antenna at 1800 MHz with the additional modulation which was identical to that generated by mobile phone GSM 1800. Rats were given 15 min exposure, or were sham-exposed with no voltage applied to the field generator in control groups. Immediately before EMF exposure, rats were injected intraperitoneally with tramadol in the 20 mg/kg dose or vehicle in the 1 ml/kg volume. RESULTS Our study revealed that single EMF exposure in 1800 MHz frequency significantly reduced antioxidant capacity both in healthy animals and those with paw inflammation. A certain synergic mode of action between applied electromagnetic fields and administered tramadol in rats treated with CFA was observed. CONCLUSIONS The aim of the study was to examine the possible, parallel/combined effects of electromagnetic radiation, artificially induced inflammation and a centrally-acting synthetic opioid analgesic drug, tramadol, (used in the treatment of severe pain) on the antioxidant capacity of blood of rats. The antioxidant capacity of blood of healthy rats was higher than that of rats which received only tramadol and were exposed to electromagnetic fields.

Surface-enhanced Raman spectroscopy and electrochemistry at the copper ∣ 4-phenylpyridine interface

Abstract The adsorption of 4-phenylpyridine (4-PhPy) on copper was examined by means of cyclic voltammetry and surface-enhanced Raman spectroscopy (SERS) in a wide range of electrode potentials. Electrochemical results revealed that anodic dissolution of copper as well as the cathodic evolution of hydrogen are inhibited in the presence of chemisorbed 4-PhPy molecules in both neutral and acidic solutions. An abrupt change of the spectral pattern was observed in the SERS spectra of neutral solutions of 4-PhPy at potentials more negative than −0.6 V versus Ag/AgCl. An assignment of the spectrum by ab initio calculations enabled us to interpret the spectroscopic results in terms of potential-induced reorientation of the molecular plane with respect to the surface. The SERS results revealed that at more negative potentials the adsorbed molecules stand vertically on the surface and self-assemble into molecular stacks. In intermediate potentials, molecules are adsorbed in a flat configuration. A vertical configuration reappears at positive potential values.

A smart synthesis of gold/polystyrene core-shell nanohybrids using TEMPO coated nanoparticles†

This paper describes a novel route to the synthesis of core–shell nanostructures utilizing Nitroxide Mediated Radical Polymerization (NMRP). The hybrid nanostructures with nanogold cores and precisely designed polystyrene shells (PDI < 1.3) have been synthesized through late injection of TEMPO coated gold nanoparticles into a TEMPOL (4-hydroxy-TEMPO) mediated styrene polymerization system. Thermal analyses have shown that the thus obtained polystyrene modified gold nanoparticles are significantly more stable to the thermal treatment than only thiol-stabilized gold nanoparticles (aggregation has not been observed even at 300 °C). The obtained materials exhibit intensive surface plasmon resonance (SPR) observed near 520 nm that provides an opportunity to apply them as high-temperature optical sensors. The proposed procedure allows for precise synthesis of tailor-made nanohybrids via macroradical coupling.

New opportunities of the application of natural herb and spice extracts in plant oils: application of electron paramagnetic resonance in examining the oxidative stability.

The aim of this study was to establish the applicability of natural water-ethanol extracts of herbs and spices in increasing the oxidative stability of plant oils and in the production of novel food. Different concentrations (0, 100, 300, 500, and 700 ppm) of spice extracts and butylated hydroxyanisole (BHA) (100 ppm) were added to the studied oils. The antioxidant activity of spice extracts was determined with electron paramagnetic resonance (EPR) spectroscopy using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. The study showed that the extracts significantly increased the oxidative stability of the examined oils when compared to one of the strongest synthetic antioxidants--BHA. The applied simple production technology and addition of herb and spice extracts to plant oils enabled enhancement of their oxidative stability. The extracts are an alternative to the oils aromatized with an addition of fresh herbs, spices, and vegetables because it did not generate additional flavors thus enabling the maintenance of the characteristic ones. Moreover, it will increase the intake of natural substances in human diet, which are known to possess anticarcinogenic properties.

Neuroprotective effects of tempol acyl esters against retinal ganglion cell death in a rat partial optic nerve crush model.

Purpose:  The aim of this study is to search for more effective derivatives of the superoxide dismutase mimetic tempol (4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl). Although tempol is neuroprotective in a rat partial optic nerve crush (PONC) model, relatively high doses are required to exert this effect.

Electrochemical and surface-enhanced Raman spectroscopy studies of 4-phenylpyridine adsorption at the gold/solution interface

The adsorption of 4-phenylpyridine (4-PhPy) on the Au electrode was examined using conventional electrochemical techniques: cyclic voltammetry and impedance measurements and also by surface enhanced Raman spectroscopy (SERS) in a wide range of electrode potentials. Electrochemical results indicate the strong adsorption of 4-Phpy molecules, particularly at the positively charged Au electrode. The wide shoulder of capacity close to the pzc suggests that the composition and/or the structure of 4-Phpy monolayer change with the sign of the surface charge on the electrode. Investigation of integrity of adsorbed layer, however, indicates that adsorbed molecules do not form tight, compact monolayer even in the case of adsorption from saturated solution. SERS spectra provided evidence for gradual, potential-induced reorientation of the molecular plane with respect to the surface, from nearly vertical in the negatively charged electrode, to more flat at the positively charged metal surface.

Evaluation of oxidative stability of vegetable oils enriched with herb extracts by EPR spectroscopy

Vegetable oils are important constituents of a healthy diet. Still, unsaturated fatty acids present in vegetable oils are susceptible to oxidation, which leads to undesirable changes in sensory, chemical and nutritional properties of oils. To prevent this problem, antioxidants are applied with herbs and spices being one of the most important sources of natural antioxidants. Electron paramagnetic resonance spectroscopy (EPR) can be used to detect free radicals, which are the short-lived intermediates of lipid oxidation, and to monitor changes in oxidation susceptibility. In this study, the ESR spin trapping technique was used as a potential method for the evaluation of the resistance to free radical formation in rapeseed and sunflower oils enriched with herb extracts. The antioxidant effect of herb extracts on vegetable oils was also investigated by measuring their ability to scavenge DPPH free radical using EPR spectroscopy. The herb extracts generally improved the radical scavenging properties of sunflower and rapeseed oils but their influence on the onset of rapid lipid oxidation as measured by spin-trapping EPR depended on the type of oil and on the extract concentration.