Helena Abramovič

In Vitro Antimicrobial and Antioxidant Activity of Commercial Rosemary Extract Formulations

Phenolic plant extracts are sources of natural bioactive compounds, which can inhibit the rate of food spoilage. MIC and MBC concentrations of four oil- or water-soluble rosemary (Rosmarinus officinalis) extracts against gram-positive (Bacillus and Staphylococcus) and gram-negative (Campylobacter and Salmonella) bacteria were determined by using disk diffusion, agar dilution, and broth microdilution methods, as well as bacterial survival kinetics in a macrodilution test. To describe the antioxidant properties of the extracts, the reducing power, free radical scavenging effectiveness, and beta-carotene bleaching test were used. The antimicrobial and antioxidant activity depended on the concentration and chemical nature of the phenolic compounds in the extracts. Gram-positive bacteria were more sensitive than were gram-negative bacteria, especially for oil-soluble extracts with carnosic acid as the major phenolic compound. A microdilution method based on ATP measurement was found to be a useful, rapid technique for determining antibacterial efficiency, and its results correlated well with MICs from survival curve measurement. Reducing power and free radical scavenging effectiveness was higher in water-soluble formulations, according to their higher total phenolic content, but in an aqueous emulsion system of linoleic acid, they exhibited lower antioxidant activity. This correlated well with the higher efficiency of antimicrobial activity of oil-soluble formulations, despite the lower total phenolic content of these extracts.

Sinapic Acid and Its Derivatives: Natural Sources and Bioactivity

 Sinapic acid is widespread in the plant kingdom (fruits, vegetables, cereal grains, oilseed crops, and some spices and medicinal plants) and as such is common in the human diet. Derivatives of sinapic acid are characteristic compounds in the Brassicaceae family. Sinapic acid shows antioxidant, antimicrobial, anti-inflammatory, anticancer, and anti-anxiety activity. 4-Vinylsyringol (a decarboxylation product of sinapic acid) is a potent antioxidative and antimutagenic agent which suppresses carcinogenesis and the induction of inflammatory cytokines. Sinapine (sinapoyl choline) is considered to be an acetylcholinesterase inhibitor which might have therapeutic applications in various disease treatments. Mainly due to their antioxidative activity, these compounds have been suggested for potential use in food processing, cosmetics, and the pharmaceutical industry, and this review aims to summarize current knowledge on the natural sources, chemistry, and biological activity of these substances.

Antioxidant properties of 4-vinyl derivatives of hydroxycinnamic acids.

The compounds 4-vinylphenol (4-VP), 4-vinylguaiacol (4-VG), 4-vinylsyringol (4-VS) and 4-vinylcatechol (4-VC) were prepared by thermal decarboxylation of the corresponding hydroxycinnamic acids p-coumaric, ferulic, sinapic and caffeic acid, respectively. For confirmation of the synthesised products LC-MS followed by NMR analysis was used. To evaluate their antioxidant potential, their reducing power and efficiency in scavenging the alkylperoxyl radical generated in an emulsion system, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and the superoxide anion radical (O2(-)) were determined. All tested 4-vinyl derivatives revealed weaker antioxidant activity in a homogeneous polar medium than the corresponding phenolic acids. In the emulsion system the activity for 4-vinyl derivatives was higher than was the activity of their corresponding phenolic acids, with 4-VG as the most active among the tested phenolic compounds.

The rheological properties of Slovenian wines

Abstract Forty samples of bottled wines from Slovenia were characterised by standard chemical analysis. The effect of temperature on their density and viscosity was studied in the temperature range from 20°C to 50°C. From the density data the expansibility coefficients at 25°C and their temperature dependence were calculated. The viscosity of wine decreases non-linearly with increasing temperature. The experimental data were fitted to some theoretical models in order to describe the temperature dependence of the viscosity of wine. A modified Andrade equation was found to best describe this dependence. The activation energy for viscous flow of wine, calculated by the Arrhenius relation, varied from 18.63 kJ mol −1 to 20.25 kJ mol −1 . Correlations between the activation energy for viscous flow and the concentrations of solutes other than ethanol were estimated. A significant correlation between the osmolality of wine and its viscosity was found for all wines investigated.

Conductivity of some tetra-n-alkylammonium salts of pectic acid

From commercially available pectin, (OBIPEKTIN AG), pectic acid was isolated by alkaline catalysed hydrolysis and physicochemically characterized. The conductivities of aqueous solutions of tetramethyl-, tetraethyl-, tetra-n-propyl- and tetra-n-butyl pectate were determined. The concentration dependence of the conductivity as well as the conductometric titration of the investigated systems exhibited typical polyelectrolyte behaviour. The mobility of the polyelectrolyte solute was found to be influenced by the nature of the counterion. The calculated values of the molar conductivity deduced on the basis of the Manning limiting law were found to be lower than the experimental ones. The fraction of free counterions was evaluated and found to depend on the concentration and on the nature of the counterion.

Contribution of SO2 to antioxidant potential of white wine

The reactivity of SO2 with the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and in Folin Ciocalteu (FC) assays was analysed under different experimental conditions. There was significantly higher reactivity between SO2 and DPPH in buffered methanol than in methanol alone. When DPPH and FC assays were performed in a mixture of caftaric acid and SO2, there were synergistic effects that were more pronounced with the FC assay. Phenolics are an important parameter of wine quality, and their accurate characterisation in wine is essential. Analysis of white wines with DPPH and FC assays overestimates the contribution of phenolics to the antioxidant potential (AOP). SO2 contributes (from 20% to 45%) to the AOP of the white wines analysed. As SO2 reactivity depends highly on buffer composition, pH, time of incubation and other compounds, e.g. phenolics and aldehydes, different experimental protocols can produce large variations in AOPs, and therefore control of experimental conditions is extremely important.

Effect of heat treatment of camelina (Camelina sativa) seeds on the antioxidant potential of their extracts.

The effect of different heat treatments of camelina (Camelina sativa) seeds on the phenolic profile and antioxidant activity of their hydrolyzed extracts was investigated. The results showed that total phenol contents increased in thermally treated seeds. Heat treatment affected also the quantities of individual phenolic compounds in extracts. Phenolics in unheated camelina seeds existed in bound rather than in free form. A temperature of 160 °C was required for release of insoluble bound phenolics, whereas lower temperatures were found to be optimal to liberate those present as soluble conjugates. The best reducing power and alkyl peroxyl radical scavenging activity in the emulsion was expressed by phenolics which were bound to the cell wall, whereas the best iron chelators and 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavengers were found to be those present in free form. The heat treatment of seeds up to 120 °C increased the reducing power and DPPH• radical scavenging ability of extracts, but negatively affected iron chelating ability and their activity in an emulsion against alkyl peroxyl radicals.

Viscosities and apparent specific volumes of pectic acid and its lithium salt in aqueous solutions

Abstract From commercially available apple pectin, pectic acid was isolated by alkaline catalysed hydrolysis and physico-chemically characterised. The densities and viscosities of aqueous solutions of pectic acid and its lithium salt were determined at concentrations up to 0.016 g cm −3 . The effect of the addition of simple salt and the degree of neutralisation on the apparent specific volume and on the limiting viscosity number of dilute aqueous solutions of pectic acid and its lithium salt was investigated

Eyring Functions of Activation for the Viscous Flow of Some Higher Alcohols in Cyclohexane Solutions

Summary. The viscosities of solutions of 1-octanol, 1-nonanol, and 1-decanol in cyclohexane up to concentrations of 1.56 molċkg−1 were determined in the temperature range from 293.15 to 333.15 K. Applying Eyring’s transition state theory, the Eyring functions of activation for the viscous flow of binary mixtures, i.e. the molar Gibbs free energy, entropy, and enthalpy were estimated. The correlation coefficients βY (Y=G, H, or S) were derived and used to discuss the initial effect of the solute on the activation parameters for the viscous flow. From the partial molar thermodynamic functions of activation and the partial molar volumetric data of solute and solvent at infinite dilution, the viscosity coefficient B was determined. For the interpretation of the experimental data, the Unified Interaction Parameter Formalism was used.Zusammenfassung. Die Viskositäten von Lösungen von 1-Octanol, 1-Nonanol und 1-Decanol in Cyclohexan wurden im Temperaturbereich von 293.15 bis 333.15 K bis zu Konzentrationen von 1.56 molċkg−1 bestimmt. Anwendung der Eyringschen Theorie des Übergangszustandes erlaubte die Abschätzung der Eyringschen Aktivierungsfunktionen für das viskose Fließen binärer Mischungen, d.h. der molaren Größen Gibbssche Energie, Entropie und Enthalpie. Anhand der Korrelationskoeffizienten βY (Y=G, H oder S) wird der Effekt des gelösten Stoffes auf die Aktivierungs-parameter diskutiert. Aus den partiellen molaren thermodynamischen Aktivierungsfunktionen des viskosen Flusses und den partiellen molaren volumetrischen Daten von Lösungsmittel und gelöstem Stoff bei unendlicher Verdünnung wurde der Viskositätskoeffizient B bestimmt. Zur Interpretation der Daten wurde der Unified Interaction Parameter-Formalismus angewandt.

Apparent molal volumes of pectic acid and some tetra-N-alkylammonium salts of pectic acid

Abstract From commercially available pectin (OBIPEKTIN AG), pectic acid was isolated by alkaline catalysed hydrolysis and physico-chemically characterised. The densities of aqueous solutions of tetramethyl-, tetraethyl-, tetra-n-propyl- and tetra-n-butylammonium pectate were determined at concentrations up to 0.016 g·cm −3 with a vibrating tube densimeter at 298 K. The concentration dependence of the derived apparent molal volumes and the influence of the nature of the counterion on the apparent molal volume was investigated. Thereby, a linear increase in the apparent molal volume, determined at the reference concentration, with increasing number of carbon atoms in the counterion was found. The experimental values of the apparent molal volumes approached a logarithmic dependence on concentration. The theoretical expression for the concentration dependence of the apparent molal volumes was interpreted on the basis of the cell-model of a polyelectrolyte solution and on the basis of infinite-line-charge theory. The experimental values of the apparent molal volumes were found to be higher than theoretical ones in the concentration range investigated.