Tibor Cserháti

Biological activity and environmental impact of anionic surfactants.

The newest results concerning the biological activity and environmental fate of anionic surfactants are collected and critically evaluated. The chemical and physicochemical parameters related to the biological activity and the field of application are briefly discussed. Examples on the effect of anionic surfactants on the cell membranes, on the activity of enzymes, on the binding to various proteins and to other cell components and on their human toxicity are presented and the possible mode of action is elucidated. The sources of environmental pollution caused by anionic surfactants are listed and the methods developed for their removal from liquid, semiliquid and solid matrices are collected. Both the beneficial and adversary effects of anionic surfactants on the environment are reported and critically discussed. It was concluded that the role of anionic surfactants in the environment is ambiguous: they can cause serous environmental pollution with toxic effect on living organisms; otherwise, they can promote the decomposition and/or removal of other inorganic and organic pollutants from the environment. The relationship between their chemical structure, physicochemical parameters, biological activity and environmental impact is notwell understood. A considerable number of data are needed for the development of new anionic surfactants and for the successful application of the existing ones to reduce the adversary and to promote beneficial effects.

Alkyl ethoxylated and alkylphenol ethoxylated nonionic surfactants: Interaction with bioactive compounds and biological effects

Nonionic surfactants are amphipathic molecules consisting of a hydrophobic (alkylated phenol derivatives, fatty acids, longchain linear alcohols, etc.) and a hydrophilic part (generally ethylene oxide chains of various length). Although not as important commercially, tertiary amine and various sugar surfactants are also nonionic surfactants. Due to their favorable physicochemical properties, nonionic surfactants are extensively used in many fields of technology and research. The application of nonionic surfactants in various biotechnological processes has been recently reviewed (1). Surfactants have been successfully used to decrease the foaming of fermentation broths during solvent extraction (2), increase the conversion of linoleic acid to its hydroperoxide (3), and enhance the rate of cellulose hydrolysis (4). Nonionic surfactants are an integral part of the majority of pesticide formulations (5). They increase the leaf retention of spray solutions (6), enhance adhesional forces of aqueous droplets on crop leaf surfaces (7), and generally improve the effectiveness of active ingredients (8,9). However, not only do surfactants influence the performance of pesticides, but the pesticides exert some effects on the fate of surfactants; for example, pesticides promote or inhibit the photolytic degradation of nonionic surfactants (10). Nonionic surfactants are also used in pharmaceuticals to increase their stability (11) and to enhance the dissolution rate of active ingredients from suppositories (12) and solid dispersions (13), for example. The pharmaceutical industry also uses nonionic surfactants to facilitate solubilization (14) and to increase the stability of drugcarrier emulsions (15). Surfactants markedly modify the particle size of precipitated drugs, too (16,17. Due to strict regulations, nonionic surfactants have only limited application in the food industry, where they are employed to change the stability of various emulsions (18) and to decrease the retrogradation of amylopectin (19). Nonionic surfactants also have been used in analytical chemistry to increase the fluorescence of dansylated amino acids (20), improve protein separation in capillary zone electrophoresis (21), and mask side effects in spectrophotometry (22). This review presents a critical evaluation of recent results of studies on the interaction of alkyl ethoxylated and alkylphenol ethoxylated nonionic surfactants with various bioactive macromolecules and with organisms. The fate of surfactants in various ecological systems has been extensively studied. Nonionic surfactants are generally easily degradable; however, in some cases the persistence of intermediates has been observed. Due to the limited scope of this review, investigations of intermediates will not be discussed in detail.

Optimisation of the microwave-assisted extraction of pigments from paprika (Capsicum annuum L.) powders

The efficiency of microwave-assisted extraction (MAE) for the extraction of colour pigments from paprika (Capsicum annuum) powders was evaluated using 30 extracting solvent mixtures. The separation efficacy and selectivity of MAE was carried out using a spectral mapping technique and the relationship between the efficacy and selectivity of extraction and the physicochemical parameters of solvent mixtures was calculated by stepwise regression analysis. The calculation results were verified experimentally by the separation of pigment fractions by high-performance liquid chromatography. It was established that both the efficacy and selectivity of MAE depend significantly on the dielectric constant of the extraction solvent mixture.

Phenoxyacetic acids : separation and quantitative determination

The various chromatographic methods suitable for the separation and quantitative determination of phenoxyalkyl acid herbicides in environmental samples are reviewed, with special emphasis being placed on sample preparation methods such as liquid-liquid, solid-phase and supercritical fluid extractions. Techniques are classified (high-performance liquid chromatography, gas-liquid chromatography, capillary zone electrophoresis, micellar electrokinetic chromatography) and discussed separately. The advantages and disadvantages of the various preparation and separation methods and their combinations are evaluated.

Polyethylene-coated silica and zirconia stationary phases in view of quantitative structure-retention relationships

SummaryRetention properties of two new high-performance liquid chromatographic (HPLC) stationary phases, polyethylene-coated silica (PECSiO2) and polyethylene-coated zirconia (PECZrO2), were compared chemometrically. Reversed phase HPLC capacity factors were determined isocratically for a carefully designed series of 25 structurally diverse solutes. Linear free energy relationship (LFER)-based solute parameters (excess molar refraction, dipolarity-polarizability, hydrogen-bond acidity and basicity, McGowan volume) and solute structural descriptors determined by physico-chemical methods (water accessible van der Waals volume, dipole moment, atomic electron excess charge) were regressed as independent variables against log capacity factors. The quantitative structure-retention relationships (QSRR) obtained show the predominating partition mechanism of separation on both phases. Both the LFER parameters and the structural parameters obtained by molecular modelling produced QSRR equations of high and practically identical retention prediction ability. It has been concluded that intermolecular interactions of the dipolarity-polarizability type manifest themselves more strongly on the silica-based phase than on the zirconia-based one. This can be due to a role of active free silanols on the silica support.

Effect of water-soluble β-cyclodextrin polymer on the lipophilicity of polymyxine examined by reversed-phase thin-layer chromatography

Abstract Thin-layer chromatography has shown that the water-soluble β-cyclodextrin polymer forms inclusion complexes with the antibiotic polymyxine, reducing its lipophilicity and its adsorption energy on silica gel. A lower dielectric constant and increasing salt concentration of the solution as well as greater cation radii counteract the complex formation.

Influence of storage conditions on the stability of monomeric anthocyanins studied by reversed-phase high-performance liquid chromatography

The effect of light, storage time and temperature on the decomposition rate of monomeric anthocyanin pigments extracted from skins of grape (Vitis vinifera var. Red globe) was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). The impact of various storage conditions on the pigment stability was assessed by stepwise regression analysis. RP-HPLC separated well the five anthocyanins identified and proved the presence of other unidentified pigments at lower concentrations. Stepwise regression analysis confirmed that the overall decomposition rate of monomeric anthocyanins, peonidin-3-glucoside and malvidin-3-glucoside significantly depended on the time and temperature of storage, the effect of storage time being the most important. The presence or absence of light exerted a negligible impact on the decomposition rate.

Interactions between cyclodextrins and cell-membrane phospholipids

Abstract The interactions between cyclodextrins (CDs) and selected cell membrane phospholipids, liposomes and human erythrocytes were studied. Non-methylated cyclodextrins did not influence the differential scanning calorimetric behaviour of phospholipids and did not increase the permeability of dipalmitoyl-phosphatidyl-choline liposomes. Dimethyl- and trimethyl- β-CD interacted with the phospholipids but the effect was negligible compared to the effect of valinomycin. Reversed-phase thin-layer chromatography revealed complex formation with dimethyl-β-cyclodextrin, but not with others. The addition of cyclodextrins up to 10 −2 mol litre −1 concentration did not modify the active or passive alkali ion transport of human erythrocytes, however, higher concentrations of added β-cyclodextrin especially dimethyl-β-cyclodextrin resulted in hemolysis.

Interaction of taxol and other anticancer drugs with hydroxypropyl-β-cyclodextrin

Abstract The interaction between 23 anticancer drugs and hydroxypropyl-β-cyclodextrin (HPβCD) was studied by reversed-phase charge-transfer thin-layer chromatography and the relative strength of interaction was calculated. HPβCD formed inclusion complexes with 15 compounds, the complex always being more hydrophilic than the uncomplexed drug. The inclusion forming capacity of drugs differed considerably according to their chemical structure. The intensity of interaction significantly increased with increasing hydrophobicity of the guest molecule, demonstrating the preponderant role of hydrophobic interactions in inclusion complex formation.

Comparison of the retention behaviour of phenol derivatives on porous graphitized and octadecylsilica columns

SummaryThe retention of 22 ring-substituted phenol derivatives on porous graphitized carbon (PGC) (eluents: acetonitrile — water and methanol — water mixtures) and on octadecylsilica (ODS) (eluents: methanol — 0.025 M KH2PO4 mixtures) was determined, and the relationship between retention and physicochemical parameters were evaluated by principal component analysis followed by two-dimensional nonlinear mapping and by cluster analysis as well as by canonical correlation analysis. Calculations proved that marked differences can be detected between the retention characteristics of PGC and ODS columns, and the electronic parameters of phenol derivatives have the highest impact on their retention. The comparison of various multivariate mathematical-statistical methods indicated that principal component analysis followed by two dimensional non-linear mapping is the most appropriate method for the evaluation of large data matrices in RP-HPLC.