Biomedical subjects

E Forgács

Publications and source records attributed to E Forgács.

At least 37 records · Page 2Linked to original sources

PubMed2000

Colour pigments of Trichoderma harzianum. Preliminary investigations with thin-layer chromatography-Fourier transform infrared spectroscopy and high-performance liquid chromatography with diode array and mass spectrometric detection.

The colour pigments of Trichoderma harzianum fermentation broth were separated and the main fractions were tentatively identified by reversed-phase thin-layer chromatography-Fourier transform infrared spectroscopy (RP-TLC-FT-IR), RP-HPLC-diode array detection and RP-HPLC-MS. It was established that the multistep gradient elution developed for RP-TLC separation of pigments can be successfully used as a pilot method for the rational design of gradient elution in RP-HPLC for the separation of the same pigments. FT-IR and MS measurements were unable to identify the exact chemical structures of the main pigment fractions, the presence of OH, =CH and C=O (RP-TLC-FT-IR) and OH and NH, substructures (RP-HPLC-MS) was confirmed. It was assumed that the main pigment fractions are oxidation polymers originating from monomer molecules containing polar substructures and double bonds in the alkyl chain which are liable for oxidation during the aerobic fermentation process.

Chromatography, High Pressure Liquid↗

PubMed2000

Separation and quantitation of colour pigments of chili powder (Capsicum frutescens) by high-performance liquid chromatography-diode array detection.

The performance of reversed-phase thin-layer (RP-TLC) and reversed-phase high-performance liquid chromatography (RP-HPLC) was compared for the separation and determination of the colour pigments of chili (Capsicum frutescens) powder using a wide variety of eluent systems. No separation of pigments was achieved in RP-TLC, however, it was established that tetrahydrofuran shows an unusually high solvent strength. RP-HPLC using water-methanol-acetonitrile gradient elution separated the chili pigments in many fractions. Diode array detection (DAD) indicated that yellow pigments are eluted earlier than the red ones and chili powder contains more yellow pigments than common paprika powders. It was established that the very different absorption spectra of pigments make the use of DAD necessary.

Capsicum↗

PubMed2000

Classification of chili powders by thin-layer chromatography and principal component analysis.

Silica gel, aluminium oxide, diatomaceous earth, polyamide, cyano, diol and amino plates have been tested for their capacity to separate the color pigments of six chili powders of different origin by both adsorption and reversed-phase thin-layer chromatography. The plates were evaluated at 340 and 440 nm wavelengths. Best separation of color pigments was obtained on impregnated diatomaceous earth layer using acetone-water 17:3 v/v eluent. It was found that the pigment composition of chili powders showed marked differences. Principal component analysis employed for the classification of the chili powders according to their pigment composition indicated that these differences can be used for the determination of the similarity or dissimilarity of the chili powders.

Capsicum↗

PubMed2000

Solid-phase extraction and high-performance liquid chromatographic separation of pigments of red wines.

The adsorption and desorption capacities of 11 different solid-phase extraction sorbents were tested for the preconcenration of pigments of various Hungarian red wines. The concentrates were evaluated by multiwavelengh spectrophotometry combined with a spectral mapping technique (SPM) and by reversed-phase high-performance liquid chromatography. The highest (10-fold) concentration of pigments was achieved on octadecylsilica sorbent. It can be used five times without losing adsorption and desorption characteristics. SPM indicated that multiwavelength spectrophotometry can be employed for the differentiation of red wines. Comparison of the chromatograms of pigments with and without preconcentration showed that preconcentration makes possible the separation and detection of pigments present in low concentration in red wines.

Chromatography, High Pressure Liquid↗

PubMed2000

Effect of sample handling on alkaloid and mineral content of aqueous extracts of greater celandine (Chelidonium majus L.).

The authors examined the extraction of alkaloids from the greater celandine (Chelidonium majus L.) by different methods (traditional pressing and tea making, microwave and supercritical fluid extraction). The extractants were water and propylene glycol. For comparison of the extraction methods, the yield was evaluated according to total alkaloid content measured by spectroscopy. The highest alkaloid yield was obtained by microwave extraction and by making tea. Distribution of the components was studied by thin-layer chromatography and densitometry. The concentration and the ratio of alkaloid components in extracts are significantly different depending on the extraction method. The solution obtained by supercritical fluid extraction contains coptisine and chelidonine, while berberine could be obtained by microwave extraction only. Extracts with high coptisine content were obtained by supercritical fluid extraction, followed by pressing and microwave extraction. Mineral element content of the drug and extracts was also determined by inductively coupled plasma atomic emission spectrometry. Element content (Na, Ca, Fe) was found to be highest in microwave extracts.

Alkaloids↗

PubMed2000

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.

Capsicum↗

PubMed2000

Relationship between the retention characteristics on an alumina column and physico-chemical parameters of some environmental pollutants.

The retention behavior of 16 environmental pollutants was studied on alumina and porous graphitized carbon (PGC) columns using n-hexane as eluent. The relationship between the logarithm of the capacity factors determined on the alumina column and the physico-chemical characteristics of the solutes was elucidated by principal component analysis (PCA) followed by two-dimensional nonlinear mapping. The 12 original variables can be reduced to four with only a 10% loss of information. The logarithm of the capacity factor formed a cluster with the hydrogen donor and acceptor properties of the solutes and their Taft's constant on the two-dimensional nonlinear map of PC loadings indicating that both steric and electronic parameters play a considerable role in the retention mechanism on alumina support. Alcohols, aromatics and chlorinated alkanes formed separate clusters on the two-dimensional nonlinear map of PC variables suggesting that their retention mechanism may be different on the alumina column. Solutes were not retained on the PGC surface proving that under normal-phase conditions the retention capacity of alumina can be higher than that of PGC.

Aluminum Oxide↗

PubMed2000

Liquid chromatography of natural pigments.

The newest results in the application of various liquid chromatographic techniques for the analysis of natural pigments in pure state and in complicated matrices are compiled. The methods employed for the separation and quantitative determination of the different pigment classes (flavonoids, coumarins, chlorophylls, etc.) are described and critically evaluated. The future trends are briefly discussed.

Chromatography, High Pressure Liquid↗

PubMed2000

The binding of amino acids to the herbicide 2,4-dichlorophenoxy acetic acid.

The interaction of amino acids with the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was studied by charge-transfer chromatography carried out on diatomaceous layers covered with different amount of 2,4-D and the effect of salts on the strength of interaction was elucidated. It was established that Arg, His, Lys, Orn, Phe and Trp binds to 2,4-D, the binding process is of saturation character. Principal component analysis proved that the concentration of 2,4-D exerts the highest impact on the interaction and the effect of salts is of secondary importance. The results suggest that these amino acid residues may account for the binding of 2,4-D to proteins and can play a considerable role in the detoxification processes by forming conjugates with 2,4-D.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2000

Simultaneous interaction of steroidal drugs with gamma- and hydroxypropyl-beta-cyclodextrin studied by charge-transfer chromatography.

The simultaneous interaction of 15 steroidal drugs with tau-cyclodextrin (tauCD) and hydroxypropyl-beta-CD (HPbetaCD) was determined by charge transfer chromatography and the relative strength of interaction was calculated for each drug-tauCD-HPbetaCD ternary complex. The mixture of CDs interacted with each steroidal drugs decreasing the lipophilicity of the guest molecules. The chemical structure of steroidal drugs markedly influenced their capacity to interact with the mixture of CDs, the more lipophilic compounds formed stronger complexes with CDs. In the overwhelming majority of cases the stability of drug-tauCD-HPbetaCD system was higher than those of binary (drug-tauCD and drug-HPbetaCD) system indicating the probability of ternary complex formation. The data indicated that the ternary complex formation has to be taken into consideration in pharmaceutical formulations containing more than one type of CD or CD derivatives.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2000

Separation and identification of volatile components in the fermentation broth of Trichoderma atroviride by solid-phase extraction and gas chromatography-mass spectrometry.

A preseparated fermentation broth of Trichoderma atroviride strain 11 is analyzed by gas chromatography followed by mass-spectral detection using a Finnigan MAT GCQ apparatus. After preseparation in a C18 and a silica gel column, nineteen pyrone and dioxolane derivatives and two aliphatic esters are obtained, respectively. Among these, the four dioxolane derivatives have not been identified previously. The main component is found to be 5,5'-dimethyl-2H-pyran-2-on. The relative standard deviation for the determination of the retention time and the peak area (measured in ion counts) is 0.1% and 4.5%, respectively.

Culture Media↗

PubMed2000

Separation and tentative identification of the main pigment fraction of raisins by thin-layer chromatography-Fourier transform infrared and high-performance liquid chromatography-ultraviolet detection.

The soluble color pigments of raisin are separated by reversed-phase thin-layer chromatography (TLC), and the capacity of TLC-Fourier transform infrared (FTIR) with both on-line and off-line coupling is assessed for the identification of the main fraction. TLC has also been used as a pilot technique for the development of a gradient elution method for the separation of pigments by high-performance liquid chromatography (HPLC). On-line TLC-FTIR cannot be used for identification because of the strong adsorbance of the stationary phase. Off-line TLC-FTIR combined with the retention behavior of the main pigment fraction indicates that it is a polymer, caramel-like compound composed of erythrose and fructose monomers. Baseline separation of pigments is achieved by HPLC using TLC as a pilot method.

Chromatography, High Pressure Liquid↗

PubMed2000

Charge-transfer chromatographic study of the interaction of antibiotics with cetyltrimethylammonium bromide.

The interaction of 20 antibiotics with the cationic surfactant cetyltrimethylammonium bromide (CTAB) was studied by charge-transfer reversed-phase chromatography carried out on impregnated alumina layers using water-methanol mixtures as eluents. The lipophilicity and specific hydrophobic surface area of antibiotics and the relative strength of their interaction with CTAB was calculated. CTAB interacted with 10 antibiotics the antibiotic--CTAB complex generally being more hydrophilic than the uncomplexed molecule. The relative strength of interaction depended considerably on the molecular structure of the antibiotics. Significant linear correlation was found between the lipophilicity of antibiotics and their capacity to interact with CTAB indicating the involvement of hydrophobic forces in the interaction.

Anti-Infective Agents, Local↗

PubMed1999

Influence of salt and pH on the hydrophobicity parameters of antisense nucleosides studied by reversed-phase thin-layer chromatography and multivariate mathematical-statistical methods.

The lipophilicity and specific hydrophobic surface area of 12 8-substituted 2'-deoxyadenosine and 17 5-substituted-2'-deoxyuridine derivatives were determined by reversed-phase thin-layer chromatography in ion-free eluents and in eluents containing sodium chloride, sodium acetate and acetic acid. The strength and selectivity of the effect of eluent additives were separated by use of spectral mapping technique followed by two-dimensional nonlinear mapping. The relationship between the structural characteristics and hydrophobicity parameters was elucidated by stepwise regression analysis. Eluent additives exert a considerable influence on both hydrophobicity parameters. The effect of sodium chloride and acetic acid was higher than that of sodium acetate. The strength and selectivity of the sensitivity of nucleosides towards eluent additives significantly depended on the character of the ring structure and on the length of the apolar alkyl chain. The influence of the degree of unsaturation and the branching of the alkyl substituent was negligible.

Chromatography, Thin Layer↗

PubMed1999

Interaction of some steroid drugs with beta-cyclodextrin polymer.

The interaction of 15 steroidal drugs with a water-soluble beta-cyclodextrin polymer was studied by reversed-phase thin-layer chromatography in the absence and in the presence of 0.1 M sodium chloride. The relative strength of interaction was calculated and the relationship between the hydrophobicity parameters of the drugs and the strength of the drug-beta-cyclodextrin polymer was elucidated by principal component analysis. Drugs readily formed inclusion complexes with the cyclodextrin derivatives; the strength of the interaction was higher in the presence of sodium chloride. It was assumed that the formation of inclusion complexes may influence the behaviour of the drugs resulting in modified biological efficacy.

Chemical Phenomena↗

PubMed1999

Effect of salt concentration and pH on the hydrophobicity parameters of surfactants studied by TLC and spectral mapping technique.

The lipophilicity and specific hydrophobic area of 56 surfactants having different hydrophobic moiety and different length of ethylene oxide chain were determined by reversed-phase thin-layer chromatography and the strength and selectivity of the effect of sodium chloride and pH on the hydrophobicity parameters was elucidated using spectral mapping technique followed by two-dimensional nonlinear mapping. In each instance significant linear correlations were found between the lipophilicity and specific hydrophobic surface area of surfactants suggesting that from a chromatographic point of view they behave as a homologous series of solutes. It was established that the strength of the effect of both salt concentration and pH is relatively low and the selectivity of their influence on the hydrophobicity parameters is markedly different.

Chemistry, Physical↗

PubMed1999

Determination of the relative impact of chromatographic conditions and solute structures on the retention behaviour of non-ionic surfactants in RP-HPLC.

The retention behaviour of non-ionic surfactants containing different hydrophobic moiety and various lengths of polar ethylene oxide chain was studied on RP-8 and RP-18 columns using methanol and acetonitrile as organic modifiers. The relative impact of the chromatographic conditions on the retention strength was determined using stepwise regression analysis. Non-ionic surfactants can be separated according to the character of the hydrophobic moiety, but not according to the length of the polar ethylene oxide chain. Calculations proved that the organic modifier exerted the highest impact on the retention; the effect of the number of carbon atoms in the hydrophobic moiety, column temperature and the length of the hydrophobic ligand on the surface of silica support are of secondary importance.

Chromatography, High Pressure Liquid↗

PubMed1999

Relationship between hydrophobicity parameters and the strength and selectivity of phytotoxicity of sulfosuccinic acid esters.

The strength and selectivity of the phytotoxicity of 11 sulfosuccinic acid ester surfactants were determined on the leaves of Tradescantia bicolor, and the data were evaluated by multivariate mathematical-statistical methods. Spectral mapping technique combined with stepwise regression analysis indicated that both the strength and the selectivity of the effect depend significantly on the specific hydrophobic surface area of the anionic surfactants determined in the presence of ions. The significant relationship between this hydrophobicity parameter and phytotoxic activity suggests the involvement of apolar (hydrophobic) forces in the plant-surfactant interaction. It was assumed that the apolar alkyl chains of the surfactants may insert in the hydrophobic part of the phospholipid bilayers causing membrane disorder and malfunction.

Esters↗