Comparison of the degradation mechanisms of diclofenac in the presence of iron octacarboxyphthalocyanine and myeloperoxidase.

The degradation process of diclofenac (DCF) by hematoprotein myeloperoxidase (MPO) and iron octacarboxyphthalocyanine (FePcOC) in the presence of hydrogen peroxide was compared. During the oxidation of diclofenac, in the presence of iron octacarboxyphthalocyanine (FePcOC) and hydroxyl radicals (HO•) (from H2O2), an intermediate product (dimer with an m/z value of 587) with the characteristic yellow colouration and an intense band at λmax = 451 nm is formed. Iron octacarboxyphthalocyanine oxidises in the presence of hydrogen peroxide, following the first-order reaction kinetics for FePcOC and H2O2. The concentration of diclofenac does not affect the initial reaction rate. For comparison, the oxidation of DCF in the presence of myeloperoxidase and hydrogen peroxide also provided yellow-coloured solutions with an absorption maximum at λmax = 451 nm. However, LC-MS/MS analysis indicates the presence of at least seven main products of the diclofenac oxidation process in the final reaction mixture, including two dimers with the ion mass [M-H]¯ = 587.01. The mechanism of the diclofenac degradation with hematoprotein myeloperoxidase is more complex than with iron octacarboxyphthalocyanine. Furthermore, the biological activity of diclofenac and DCF dimer (iron octacarboxyphthalocyanine and hydroxyl radicals degradation product) was tested. In this case, the long-term assayed in vitro against E. coli, colorectal HCT116 and melanoma Me45 cancer cells were performed.

HPLC-DAD profile of phenolic compounds and In vitro antioxidant activity of Ficus carica L. fruits from two Algerian varieties.

Ficus carica L., commonly known as the fig tree, is a plant belonging to the Moraceae family whose fruits are traditionally used for edible and therapeutic purposes. The study aimed to investigate the lyophilized aqueous extracts of two native Algerian fig varieties, azendjar (Az) and taamriouth (Ta), as a potential source of antioxidant compounds for possible use as ingredients in pharmaceuticals or nutraceuticals. The HPLC-DAD analysis revealed the presence of two phenolic acids (3,4-dihydroxybenzoic acid and vanillic acid) and two flavonoids (rutin and quercetin) at levels 3.67, 4.80, 84.16, and 6.87 µg/g respectively for Az variety extract, and 6.90, traces, 7.46 and 3.37 µg/g respectively for Ta variety extract. Total phenolic content was determined using the Folin-Ciocalteu method at levels 951.06 ± 61.08 and 730.88 ± 45.25 GAE mg/100 g of the dry extract. In contrast, the total flavonoid content was determined using Christ-Müller's method at levels 428.34 ± 15.42 and 307.63 ± 7.94 QE mg/100 g of dry extract in the Az and Ta varieties, respectively. The total polyphenolic content of the extract may be responsible for its antioxidant action. The gathered results indicate that the extracts from the dark peel fig variety - azendjar, are characterized by a higher content of phenolic and flavonoid compounds and antioxidant activity than the extract from the light peel variety - taamriouth. In conclusion, the conducted studies and in vitro assays indicate that the studied extracts are a source of natural antioxidants and can be considered functional raw materials for producing food supplements and pharmaceuticals.

Determination of Glyphosate and AMPA in Food Samples Using Membrane Extraction Technique for Analytes Preconcentration.

The method for determining glyphosate (NPG) and its metabolite AMPA (aminomethyl phosphonic acid) in solid food samples using UAE-SLM-HPLC-PDA technique was developed. Firstly, ultrasonic-assisted solvent extraction (UAE) and protein precipitation step were used for the analyte isolation. Then, the supernatant was evaporated to dryness and redissolved in distilled water (100 mL). The obtained solution was alkalized to pH 11 (with 1 M NaOH) and used directly as donor phase in SLM (supported liquid membrane) extraction. The SLM extraction was performed using 2 M NaCl (5 mL) as an acceptor phase. The flow rate of both phases (donor and acceptor) was set at 0.2 mL/min. The membrane extraction took 24 h but did not require any additional workload. Finally, the SLM extracts were analyzed using the HPLC technique with photo-diode array detector (PDA) and an application of pre-column derivatization with p-toluenesulfonyl chloride. Glyphosate residues were determined in food samples of walnuts, soybeans, barley and lentil samples. The LOD values obtained for the studied food were 0.002 µg g-1 and 0.021 µg g-1 for NPG and AMPA, respectively. Recoveries values ranged from 32% to 69% for NPG, 29% to 56% for AMPA and depended on the type of sample matrix. In the case of buckwheat and rice flour samples, the content of NPG and AMPA was below the detection level of a used analytical method.

Oxidation of diclofenac in the presence of iron(II) octacarboxyphthalocyanine.

This paper presents the results of the research on the influence of catalytic activity of iron(II) octacarboxyphthalocyanines (FePcOC) on the transformation of diclofenac (DCF) which is the most popular anti-inflammatory analgesic. Diclofenac poses a serious threat to the natural environment. The paper demonstrates that diclofenac, in the presence a monomeric form of iron octacarboxyphthalocyanine and hydroxyl radicals (HO•) (from H2O2), undergoes a transformation into diclofenac-2,5-iminoquinone (DCF-2,5-IQ), causing distinct changes in the UV-Vis absorption spectrum. In the presence of iron octacarboxyphthalocyanine and H2O2, the previously colourless diclofenac solution becomes intense orange. As a result, a new band at approx. 450 nm appears in the absorption spectrum. HPLC analysis has shown that the concentration of diclofenac decreases with time. TD-DFT calculations using the CAM-B3LYP/6-31+G (d, p) method have been conducted to confirm experimental data concerning the formation of a new band at λmax = 450 nm.

Direct Analysis of Psilocin and Muscimol in Urine Samples Using Single Drop Microextraction Technique In-Line with Capillary Electrophoresis.

The fully automated system of single drop microextraction coupled with capillary electrophoresis (SDME-CE) was developed for in-line preconcentration and determination of muscimol (MUS) and psilocin (PSC) from urine samples. Those two analytes are characteristic active metabolites of Amanita and Psilocybe mushrooms, evoking visual and auditory hallucinations. Study analytes were selectively extracted from the donor phase (urine samples, pH 4) into the organic phase (a drop of octanol layer), and re-extracted to the acidic acceptor (background electrolyte, BGE), consisting of 25 mM phosphate buffer (pH 3). The optimized conditions for the extraction procedure of a 200 µL urine sample allowed us to obtain more than a 170-fold enrichment effect. The calibration curves were linear in the range of 0.05-50 mg L-1, with the correlation coefficients from 0.9911 to 0.9992. The limit of detections was determined by spiking blank urine samples with appropriate standards, i.e., 0.004 mg L-1 for PSC and 0.016 mg L-1 for MUS, respectively. The limits of quantification varied from 0.014 mg L-1 for PSC and 0.045 mg L-1 for MUS. The developed method practically eliminated the sample clean-up step, which was limited only to simple dilution (1:1, v/v) and pH adjustment.

The Formation of Glycerol Oligomers with Two New Types of End Groups in the Presence of a Homogeneous Alkaline Catalyst.

The purpose of this work was to synthesize and characterize oligoglycerols with the chains of more than four repeating units. Those oligoglycerols may have some interesting applications, among others, as polyoxyalkylation starters. The glycerol oligomerization process was carried out during 12 h, at 230 °C, under the pressure of 0.4 bar, with the use of sodium carbonate as a homogeneous basic catalyst; various concentrations of the catalyst in the reaction medium were used. The reaction products were analyzed with the use of direct infusion electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (13C NMR) and Fourier transform infrared spectroscopy (FTIR) techniques. Based on the analytical findings, the compositions of the obtained product mixtures and the structures of oligoglycerols present in individual fractions were determined. The effect of catalyst concentration on the composition of the post-reaction mixture was observed. Moreover, in addition to the conventional linear oligomers (α,α-oligoglycerols), two new types of the oligomers were for the first time detected in the post-reaction mixture: one with two hydroxyl groups and the other with a carboxylate group at the α-carbon atom.

The application of the supported liquid membrane and molecularly imprinted polymers as solid acceptor phase for selective extraction of biochanin A from urine.

An efficient sample clean-up and preconcentration procedure for phytoestrogens analysis in urine has been developed. It was based on a combination of solid phase extraction with hollow-fiber supported liquid membrane and molecularly imprinted beads (MIPs-HF-SLM-SPE). The molecularly imprinted polymers (MIPs) were synthesized by precipitation polymerization technique with biochanin A (BCA) as a template, giving narrowly dispersed microspheres with a regular shape. As the functional monomer, (dimethylamino)ethyl methacrylate (-DEM) turned out to be better than methacrylic acid (MAA) to get the best-imprinted effects. The MIPs used as sorbents in the MIPs-HF-SLM-SPE extraction process exhibited excellent binding selectivity for BCA, in comparison to non-imprinted polymers as well as its structural analogs (genistein and daidzein). Finally, the developed method was used to detect BCA in urine. Under optimal extraction conditions, the recovery of BCA in urine samples (using 4.5 mL sample spiked with 10 µg L-1) was over 41%, with a coefficient of variation (CV) < 6.6% (n = 5). The detection limit (LOD) and quantification limit (LOQ) for BCA analysis in urine were 0.41 and 1.36 µg L-1, respectively.

'Structural constraints in cyanobacteria-mediated whole-cell biotransformation of methoxylated and methylated derivatives of 2'-hydroxychalcone.

Halophilic and freshwater strains of cyanobacteria representing the Oscillatoriales, Nostocales, Chroococcales, and Synechococcales orders of Cyanophyta were examined to determine (i) the resistance of their cultures when suppressed by the presence of exogenous methoxylated and methylated derivatives of 2'-hydroxychalcone, (ii) morphological changes in cells treated with the tested chalcones and, most importantly, (iii) whether these photoautotrophic microorganisms transform chalcone derivatives in a structure- or strain-dependent manner. The growth of cyanobacterial cultures depended on chalcone derivatives and the strain; nevertheless, trends for correlations between these parameters are difficult to determine. The exposure of cyanobacteria to the tested chalcones revealed severe membrane damage that was consistent with the disruption of membrane integrity. All examined blue-green algae transformed methoxy derivatives of 2'-hydroxychalcone via hydrogenative bio-reduction and formed the corresponding hydroxydihydro derivatives with various efficiencies (≤1 - 70%), depending more on the structure than on the strain. We observed dependency of the routes and efficiency of biohydrogenation of tested chalcones on the location of the methoxyl substituent and, to a lesser extent, on cyanobacterial strains. 2'-hydroxy-4″-methylchalcone was also converted by cyanobacteria to various products, amongst which the most interesting were 2'-ethoxy derivatives. The final products of biocatalytic transformation were extracted from the cyanobacterial media, separated by high performance thin-layer chromatography (HPTLC) and identified by a combination of liquid chromatography-tandem mass spectrometry (LC-MS/MS technique) and one-dimensional (1D 1H and 13C) and two-dimensional (2D HSQC and COSY) nuclear magnetic resonance (NMR) spectroscopy.

2-(1,3-Oxazolin-2-yl)pyridine and 2,6-bis(1,3-oxazolin-2-yl) pyridine.

The data presented in this article are related to research articles "Titanium and vanadium catalysts with oxazoline ligands for ethylene-norbornene (co)polymerization (Ochedzan-Siodlak et al., 2018). For the title compounds, 2-(1,3-oxazolin-2-yl)pyridine (Py-ox) and 2,6-bis(1,3-oxazolin-2-yl)pyridine (Py-box), the single-crystal X-ray diffraction measurement together with NMR, GC, MS, DSC analysis, like also the method of crystallization are presented.

Secondary metabolites from the aerial parts of Cytisus villosus Pourr.

Phytochemical investigation of the aerial parts of Cytisus villosus Pourr. resulted in the isolation and characterization of a new isoflavan, (3S, 4S)-2',4'-dihydroxy-3'-methoxy-6,7-methylenedioxyisoflavan- 4-ol (1), and a new monoterpene, (4R,6S)-4-hydroxy-2,2,6-trimethyl-9-oxabicyclo [4.2.1] non-1(8)-en-7-one (2), together with four known flavonoids: geinstein (3), chrysin (4), chrysin -7-O-ß-D-glucopyranoside (5) and 2″-O-α-L-rhamnosylorientin (6). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis, including 1D, 2D NMR (1H, 13C, COSY, TOCSY, HMBC and HSQC) and HRESIMS. The absolute configurations of 1 and 2 were established by the comparison of experimental and calculated electronic circular dichroism (ECD) spectra.

Biocatalytic hydrogenation of the C=C bond in the enone unit of hydroxylated chalcones-process arising from cyanobacterial adaptations.

To verify the hypothesis that cyanobacteria naturally biosynthesising polyphenolic compounds possess an active enzymatic system that enables them to transform these substances, such an ability of the biocatalytic systems of whole cells of these biota was assessed for the first time. One halophilic strain and seven freshwater strains of cyanobacteria representing four of the five taxonomic orders of Cyanophyta were examined to determine the following: (i) whether they contain polyphenols, including flavonoids; (ii) the resistance of their cultures when suppressed by the presence of exogenous hydroxychalcones-precursors of flavonoid biosynthesis and (iii) whether these photoautotrophs can transform hydroxylated chalcones. All examined strains were found to contain polyphenols and flavonoids, and the growth of their cultures was inhibited in the presence of 2'-hydroxychalcone, 2″-hydroxychalcone and 4″-hydroxychalcone. We also confirmed that the examined cyanobacteria transformed hydroxychalcones via hydrogenative bio-reduction and formed the corresponding hydroxydihydro derivatives with yields above 90% whenever the substrates were bioavailable for such a conversion. Moreover, we observed that the routes and efficiency of biohydrogenation (and hydroxylation) of chalcones were dependent on the location of the hydroxyl substituent. The final products obtained as the results of biotransformations were extracted from the media and identified by mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (1H NMR, 13C NMR, COSY, HSQC). Based on those results, we believe that the very efficient biohydrogenation of hydroxychalcones, which may easy be scaled up for biotechnological purposes, reflects the natural activity of the cyanobacterial defence system, because hydroxydihydrochalcones were less active inhibitors of the growth of cyanobacterial cultures than the corresponding substrates.

Multivariate optimization of the hollow fibre liquid phase microextraction of muscimol in human urine samples.

A liquid phase microextraction based on hollow fibre followed by liquid chromatographic determination was developed for the extraction and quantitation of the hallucinogenic muscimol from urine samples. Method applicability on polar hallucinogens was also tested on two alkaloids, a psychedelic hallucinogen, tryptamine and a polar amino acid, tryptophan which exists in its charged state in the entire pH range. A multivariate design of experiments was used in which a half fractional factorial approach was applied to screen six factors (donor phase pH, acceptor phase HCl concentration, carrier composition, stirring rate, extraction time and salt content) for their extent of vitality in carrier mediated liquid microextractions. Four factors were deemed essential for the effective extraction of each analyte. The vital factors were further optimized for the extraction of single-spiked analyte solutions using a central composite design. When the simultaneous extraction of analytes was performed under universal factor conditions biased towards maximizing the enrichment of muscimol, a good composite desirability value of 0.687 was obtained. The method was finally applied on spiked urine samples with acceptable enrichments of 4.1, 19.7 and 24.1 obtained for muscimol, tryptophan and tryptamine respectively. Matrix-based calibration curves were used to address matrix effects. The r(2) values of the matrix-based linear regression prediction models ranged from 0.9933 to 0.9986. The linearity of the regression line of the matrix-based calibration curves for each analyte was directly linked to the analyte enrichment repeatability which ranged from an RSD value of 8.3-13.1%. Limits of detection for the developed method were 5.12, 3.10 and 0.21ngmL(-1) for muscimol, tryptophan and tryptamine respectively. The developed method has proven to offer a viable alternative for the quantitation of muscimol in human urine samples.

Research on acute toxicity and the behavioral effects of methanolic extract from psilocybin mushrooms and psilocin in mice.

The pharmacological activities and acute toxicity of the psilocin (PC) and dried residues of the crude extracts of psychotropic mushrooms were investigated in mice. The hallucinogenic substances were effectively isolated, by using methanol, from the species of Psilocybe semilanceata and Pholiotina cyanopus, that were collected in the north-east region of Poland. The chemical analysis of these extracts, which was performed by liquid chromatography with mass spectrometry detection (LC-MS), indicated the presence of psilocin and other hallucinogenic substances, including indolealkylamines and their phosphorylated analogues. When the pure psilocin or fungal extracts were used, slight differences in determined LD50 values were observed. However, the application of PC evoked the highest level of toxicity (293.07 mg/kg) compared to the activity of extracts from Ph. cyanopus and P. semilanceata, where the level of LD50 was 316.87 mg/kg and 324.37 mg/kg, respectively. Furthermore, the behavioral test, which considered the head-twitching response (HTR), was used to assess the effects of the studied psychotropic factors on the serotonergic system. Both, the fungal extracts and psilocin evoked characteristic serotoninergic effects depending on the dose administered to mice, acting as an agonist/partial agonist on the serotonergic system. A dose of 200 mg/kg 5-hydroxytryptophan (5-HTP) induced spontaneous head-twitching in mice (100% effect), as a result of the formation of 5-hydroxytryptamine (5-HT) in the brain. Compared to the activity of 5-HTP, the intraperitoneal administration of 1mg/kg of psilocin or hallucinogenic extracts of studied mushrooms (Ph. cyanopus and P. semilanceata) reduced the number of head-twitch responses of about 46% and 30%, respectively. In contrast, the administration of PC exhibited a reduction of about 60% in HTR numbers.

Surface molecularly imprinted silica for selective solid-phase extraction of biochanin A, daidzein and genistein from urine samples.

Selective molecularly imprinted silica polymer (SiO2MIP) for extraction of biochanin A, daidzein and genistein was synthesized using the surface molecular imprinting technique with the silica gel as a support. Biochanin A (BCA) was used as a template, 3-aminopropyltriethoxysilane (APTES) as a functional monomer, and tetraethoxysilicane (TEOS) as a cross-linker. Non-imprinted polymer with the sol-gel process (SiO2NIP) was also prepared for comparison. The synthesized polymers were characterized by Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) and a standard Brunauer-Emett-Teller (BET) and Barret-Joyner-Halenda (BJH) analysis. The obtained results indicated the structural differences between imprinted and non-imprinted polymers. Finally, the SiO2MIP and SiO2NIP were adopted as the adsorbents of solid phase extraction for isolation and preconcentration of biochanin A and its structural analogues-daidzein and genistein from aqueous and urine samples. The performance analysis revealed that SiO2MIP displayed better affinity to the three investigated isoflavones compared with SiO2NIP. The recoveries of spiked samples for studied analytes ranged from 65.7% to 102.6% for molecularly imprinted silica polymer and 8.9-16.0% for non-imprinted sorbents.

Characterization of particle morphology of biochanin A molecularly imprinted polymers and their properties as a potential sorbent for solid-phase extraction.

Molecularly imprinted polymers (MIPs) with biochanin A as a template were obtained using a bulk polymerization with non-covalent imprinting approach. The polymers were prepared in acetonitrile as porogen, using ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The synthesis, with an application of 1',1'-azobis(cyclohexanecarbonitrile) (ACHN) as an initiator, has been performed thermally. During the synthesis process the effect of different functional monomers such as methacrylic acid (MAA), acrylamide (AA) and 4-vinylpyridine (4-VP) was investigated. The application of nitrogen sorption porosimetry, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) permitted the characterization and evaluation of synthesized polymers. The adsorption capacity of obtained MIPs was checked by using the binding testing. All synthesized polymers were evaluated as solid-phase extraction (SPE) sorbents for isolation and preconcentration of biochanin A and its analogues, daidzein and genistein. The MIPs exhibited higher affinity for biochanin A over competitive compounds.

Do differences in chemical composition of stem and cap of Amanita muscaria fruiting bodies correlate with topsoil type?

Fly agaric (Amanita muscaria) was investigated using a 1H NMR-based metabolomics approach. The caps and stems were studied separately, revealing different metabolic compositions. Additionally, multivariate data analyses of the fungal basidiomata and the type of soil were performed. Compared to the stems, A. muscaria caps exhibited higher concentrations of isoleucine, leucine, valine, alanine, aspartate, asparagine, threonine, lipids (mainly free fatty acids), choline, glycerophosphocholine (GPC), acetate, adenosine, uridine, 4-aminobutyrate, 6-hydroxynicotinate, quinolinate, UDP-carbohydrate and glycerol. Conversely, they exhibited lower concentrations of formate, fumarate, trehalose, α- and ß-glucose. Six metabolites, malate, succinate, gluconate, N-acetylated compounds (NAC), tyrosine and phenylalanine, were detected in whole A. muscaria fruiting bodies but did not show significant differences in their levels between caps and stems (P value>0.05 and/or OPLS-DA loading correlation coefficient <0.4). This methodology allowed for the differentiation between the fruiting bodies of A. muscaria from mineral and mineral-organic topsoil. Moreover, the metabolomic approach and multivariate tools enabled to ascribe the basidiomata of fly agaric to the type of topsoil. Obtained results revealed that stems metabolome is more dependent on the topsoil type than caps. The correlation between metabolites and topsoil contents together with its properties exhibited mutual dependences.

Determination of muscimol and ibotenic acid in mushrooms of Amanitaceae by capillary electrophoresis.

In this study, the CZE method for rapid quantitative and qualitative determination of ibotenic acid and muscimol in Amanita mushrooms naturally grown in Poland was developed. The investigations included the species of A. muscaria, A. pantherina, and A. citrina, collected in southern region of Poland. The studied hallucinogenic compounds were effectively extracted with a mixture of methanol and 1 mM sodium phosphate buffer at pH 3 (1:1 v/v) using ultrasound-assisted procedure. The obtained extracts were separated and determined by CZE utilizing a 25 mM sodium phosphate running buffer adjusted to pH 3 with 5% content of acetonitrile v/v. The calibration curves for both analytes were linear in the range of 2.5-7000 µg/mL. The intraday and interday variations of quantitative data were 1.0 and 2.5% RSD, respectively. The recovery values of analyzed compounds were over 87%. The identities of ibotenic acid and muscimol were confirmed by UV spectra, migration time, and measurements after addition of external standard.

Characterization of hydrocarbon-degrading and biosurfactant-producing Pseudomonas sp. P-1 strain as a potential tool for bioremediation of petroleum-contaminated soil.

The Pseudomonas sp. P-1 strain, isolated from heavily petroleum hydrocarbon-contaminated soil, was investigated for its capability to degrade hydrocarbons and produce a biosurfactant. The strain degraded crude oil, fractions A5 and P3 of crude oil, and hexadecane (27, 39, 27 and 13% of hydrocarbons added to culture medium were degraded, respectively) but had no ability to degrade phenanthrene. Additionally, the presence of gene-encoding enzymes responsible for the degradation of alkanes and naphthalene in the genome of the P-1 strain was reported. Positive results of blood agar and methylene blue agar tests, as well as the presence of gene rhl, involved in the biosynthesis of rhamnolipid, confirmed the ability of P-1 for synthesis of glycolipid biosurfactant. 1H and 13C nuclear magnetic resonance, Fourier transform infrared spectrum and mass spectrum analyses indicated that the extracted biosurfactant was affiliated with rhamnolipid. The results of this study indicate that the P-1 and/or biosurfactant produced by this strain have the potential to be used in bioremediation of hydrocarbon-contaminated soils.

Supported liquid membrane extraction with single hollow fiber for the analysis of fluoroquinolones from environmental surface water samples.

In this work, the simple analytical method for the determination of four fluoroquinolone antibiotics: ciprofloxacin, enrofloxacin, norfloxacin and danofloxacin, in environmental surface water samples is described. Sample pretreatment step was performed by the application of a technique based on supported liquid membrane extraction with the configuration of single hollow fiber (HF-SLM). The HPLC system with diode array detection was used for final analysis of studied analytes. Various parameters affecting the extraction efficiency during HF-SLM enrichment, such as type of membrane diluent, pH of donor (sample) and acceptor phases, as well as an enrichment time and salt content of sample were studied. Using the presented hollow-fiber extraction high recovery (70-80%) was achieved. It gave enrichment factor above 100. The detection limits in surface water samples, for the four target antibiotics, were at range 0.01-0.02 microg/l, when 10 ml samples were processed. The obtained results demonstrate the applicability of presented method for the selective extraction of fluoroquinolones in environmental water samples at ultratrace level. Errors, expressed as relative standard deviation (RSD) were below 8%, for all tested concentration levels.

Sample pretreatment techniques for oligopeptide analysis from natural sources.

The analysis of oligopeptides in samples of food, tissues, and body fluids attracts considerable attention. The complexity of such samples requires efficient sample preparation (i.e., concentration and cleanup) procedures to remove interfering endogenous compounds and inorganic or organic salts. The methods of sample pretreatment that enable effective and selective isolation and/or preconcentration of oligopeptides from complex sample matrices have been reviewed. In each case, examples of application were presented and discussed, taking into account selectivity, enrichment, method automation, cleanup, and environmental aspects of the developed methods.