Milena Bártlová

Bulgarian Academy of Sciences, Sofia, Oblast Sofiya-Grad, Bulgaria

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Publications (12)20.27 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The extracts of valuable vegetable oils containing a number of minor components (sterols, tocopherols, carotenoids, etc.) have added value as pharmaceuticals and food additives. Beta-sitosterol (BS) as minor component of vegetable oil was extracted from ground seeds of sea buckthorn with supercritical CO2 at pressures 15–60 MPa and temperatures 40–80 °C. The changes in the BS content in extract in the course of the extraction were evaluated using HPLC and described in terms of phase equilibrium. It was shown that the separation factors used in counter-current fractionation of oils apply also to the initial period of oil extraction from ground seeds. The equilibrium compositions of a model BS + trilinolein + CO2 mixture were calculated using SRK and PSRK equations of state. The BS to triacylglycerol separation factor, ranging from 1.0 to 3.1, was correlated with CO2 density.
    Journal of Food Engineering. 01/2010;
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    ABSTRACT: Leuzea carthamoides is an adaptogenic plant containing biologically active compounds as ecdysteroids and guaianolide-type sesquiterpene lactones, conventionally extracted from the plant with ethanol. It may be a potential source of the mentioned natural compounds. Ethanol-modified near-critical CO(2) was used as selective solvent with the aim to increase the level of 20-hydroxyecdysone in the extract from L. carthamoides roots and to remove selectively cynaropicrin, a sesquiterpene lactone of bitter taste, from the leaves. The extraction conditions were varied (pressure 20-28 MPa, temperature 40-60 degrees C, ethanol concentration in the solvent 0-7.1%) and the extraction yield and extract composition were compared with the results of ethanolic extraction. The supercritical fluid extraction (SFE) from finely powdered plant was controlled by phase equilibrium. Cynaropicrin was quantitatively removed from the leaves where 89% of 20-hydroxyecdysone was retained. The extraction yield of 20-hydroxyecdysone from roots with ethanol-modified CO(2 )was lower by 30% than with ethanol but its concentration in the extract was higher by 67%.
    Journal of Separation Science 06/2008; 31(8):1387-92. · 2.59 Impact Factor
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    ABSTRACT: Biologically active lignans from caulomas (stems) and leaves of Schisandra chinensis were extracted with supercritical carbon dioxide at the pressures 20–27 MPa, temperatures 40, 50 and 60 °C, and solvent-to-feed ratio 36–43. Six major lignans were determined by means of HPLC: schizandrin, gomisin A, deoxyschizandrin, γ-schizandrin, gomisin N and wuweizisu C. At the optimum conditions 27 MPa and 50 °C, the extraction yield of lignans from caulomas was 1.3% dry weight and their content in the extract was higher than 32 wt.%. At the optimum conditions for CO2 extraction from S. chinensis leaves, 27 MPa and 60 °C, the yield of lignans was 0.22% d.w. and the yield of (E)-cinnamic acid was 0.18% d.w. Addition of 2–4% ethanol to CO2 increased the extraction rate but not the final yield of lignans. The solubility of extracted substances in supercritical CO2 was estimated from their extraction rates.
    Journal of Supercritical Fluids The 01/2007; 42(1):88-95. · 2.73 Impact Factor
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    ABSTRACT: Blackcurrant (Ribes nigrum) seed oil is rich in alpha- and gamma-linolenic acids, the latter in particular being of potential use in medicine. The enzymatic hydrolysis of the oil was carried out in supercritical carbon dioxide using lipase Lipozyme as catalyst and changes in the composition of acylglycerols were recorded. Mono-, di-, and triacylglycerols and free fatty acids were separated by non-aqueous high-performance liquid chromatography in reversed phase mode and detected by UV diode array and 1H NMR detectors. Lipozyme was found to exert low specificity to individual fatty acids in the hydrolysed oil.
    Journal of Chromatography B 08/2006; 839(1-2):80-4. · 2.49 Impact Factor
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    ABSTRACT: β-Sitosterol (22,23-dihydrostigmasterol) and scopoletin (7-hydroxy-6-methoxycoumarin) were extracted from roots of stinging nettle (Urtica dioica L.) with supercritical and liquid CO2. Extraction rates were measured for both oleoresin and the individual substances in dependence on extraction conditions. The solvent modified with ethanol (0–9.4 wt.%) was applied at the pressures of 100, 200, 250 and 280 bar and the temperatures of 25, 40 and 60 °C. Extracts were analysed by means of HPLC method. The maximum yields of β-sitosterol and scopoletin were 0.63 and 0.058 mg/g dry mass, respectively. In comparison with the extract obtained with diethyl ether, the maximum yields obtained with CO2 were at least two times higher for both investigated substances. A model describing the extraction of a solute that is present in two forms, free and interacting with matrix, was applied to interpret the experimental extraction curves.
    Journal of Supercritical Fluids The 01/2005; 35(2):111-118. · 2.73 Impact Factor
  • Lubomír Opletal, Helena Sovová, Milena Bártlová
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    ABSTRACT: The drug Wuweizi (dried fruits of Schisandra chinensis or S. sphenantherd) is one of important medicinal means used in the Oriental medicine. The lignans of dibenzo[a,c]cyklooctadiene type are major constituents, a volatile oil with mono- and ses-quiterpens, an oil, organic acids and small amounts of additional compounds are also present. The content of major lignans (schizandrin, deoxyschizandrin, gomisin A, gomisin N, gamma-schizandrin, wuweizisu C) in commercially available drugs ranges usually between 3 and 5%. The present paper biefly comments the isolation and biological activity of the lignans and is especially concerned with analytical methods (TLC and HPLC) for the determination of the drug fingerprint and methods for the determination of constituents in drugs, mixtures and biological materials. HPLC methods using RP-silica bonded phases and diluted methanol, acetonitrile (or a mixture of both), are most important for these purposes. Electromigration methods are less suitable and the importance of hyphenation procedures is practically negligible.
    Journal of Chromatography B 01/2005; 812(1-2):357-71. · 2.49 Impact Factor
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    ABSTRACT: Silylation of N,O-diacylhydroxylamines with N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide produces only O-silylated products and no N-silylated derivative. Steric interactions of the substituents on the nitrogen atom with the O−N oxygen atom control the configuration on the CN bond in the product:  a Z isomer is formed almost exclusively from N-benzoylhydroxylamines, and a mixture of E and Z isomers is produced from N-acetyl derivatives. The relative stability of all isomers in various conformations was confirmed by calculations at the B3LYP/6-31G(d,p) level. The tert-butyldimethylsilyl derivatives have been fully characterized by their 1H, 13C, 15N, and 29Si NMR spectra.
    Organometallics. 03/2004; 23(9).
  • H Sovová, M Sajfrtová, M Bártlová, L Opletal
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    ABSTRACT: Chlorophylls and carotenoids were extracted from leaves of stinging nettle (Urtica dioica L.) with supercritical and liquid CO2. The solvent modified with ethanol (0–7wt.%) was applied at the pressures of 200, 250 and 280bar and the temperatures of 25, 40 and 60°C. Extracts were analysed by means of HPLC and RP-HPLC methods. The maximum yields of chlorophyll a, chlorophyll b, β-carotene and lutein obtained with CO2 were 73, 100, 24 and 39mg/100g dry matter, respectively. In comparison with the extract obtained using conventional solvents, the maximum yields obtained with CO2 were similar for carotenoids, higher for chlorophyll b and lower for chlorophyll a. Chlorophyll a partially degraded in the extractor to the more soluble pheophytin a; the extent of carotenoid degradation was much lower than that of chlorophylls. The degradation was substantially reduced by addition of a small amount of antioxidant to the solvent. Extraction rates in dependence on extraction conditions were measured both for individual pigments and for oleoresin. A model describing the extraction of a solute that is present in two forms, free and interacting with matrix, was applied to interpret the experimental extraction curves. A loss of volatile substances from the ground nettle leaves and a decrease in β-carotene content from 24 to 18mg/100g dry matter was observed during the period of 155 days between the first and last experimental run.
    Journal of Supercritical Fluids - J SUPERCRIT FLUID. 01/2004; 30(2):213-224.
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    ABSTRACT: Six major lignans (schizandrin, gomisin A, deoxyschizandrin, y-schizandrin, gomisin N, wuweizisu C) in the caulomas and leaves of Schizandra chinensis (Turcz.) Baill., and cinnamic acid in the leaves of the plant, were quantitatively analysed by high-performance liquid chromatography in reversed-phase mode with UV detection. Resolution of the determined lignans was evaluated for two multistep gradients applied. Samples for HPLC analysis were prepared by extraction with supercritical carbon dioxide at pressures of 20-27 MPa and temperatures of 40-60 degrees C. Kinetics of the extraction of individual components was measured and simulated with a model.
    Journal of Chromatography B 05/2002; 770(1-2):283-9. · 2.49 Impact Factor
  • Chemical Physics Letters 05/1996; 253(5). · 2.15 Impact Factor
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    ABSTRACT: Oil from the seed and pulp of sea buckthorn berries (Hippophaë rhamnoides L.) was extracted with carbon dioxide at pressures 9.6–27 MPa and temperatures 25–60°C. Influence of extraction conditions on solubility and mass transfer rate was studied. No marked changes in composition of extracted oil in the course of extraction were observed. Experimental extraction curves were evaluated using a model with grinding efficiency, volume mass transfer coefficients in solid and fluid phases, and parameter of flow asymmetry as adjustable parameters. The solid-phase mass transfer coefficient was increasing with rising temperature.
    Chemical Engineering Science 01/1996; 51(18):4347-4352. · 2.61 Impact Factor
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    ABSTRACT: Oleoresin was extracted from ground black pepper with carbon dioxide at 28 MPa and 24 to 60 °C. The yield and contents of piperine in the extract were determined as a function of extraction time and the solvent amount. The concentration profile of piperine inside the fixed bed of pepper was also measured. The total extract contained piperine and essential oil in the proper ratio to be used directly in food industry.The experimental results showed a strong variation of extract composition during the extraction. They were simulated using the extended Lack's model with mass transfer coefficients in the solvent and solid phase and with grinding efficiency as parameters. The parameters were determined individually for each of the three extract components, representing essential oil, piperine, and other nonpolar substances.
    Journal of Supercritical Fluids - J SUPERCRIT FLUID. 01/1995; 8(4):295-301.

Publication Stats

126 Citations
20.27 Total Impact Points

Institutions

  • 2010
    • Bulgarian Academy of Sciences
      • Institute of Chemical Engineering
      Sofia, Oblast Sofiya-Grad, Bulgaria
  • 2008
    • The Police Academy of the Czech Republic in Prague
      Praha, Praha, Czech Republic
  • 2002–2008
    • Academy of Sciences of the Czech Republic
      • Ústav chemických procesů
      Praha, Hlavni mesto Praha, Czech Republic
  • 2005
    • University of Hradec Králové
      Königgrätz, Královéhradecký, Czech Republic