Olga G Cvetković

University of Belgrade, Beograd, Central Serbia, Serbia

Are you Olga G Cvetković?

Claim your profile

Publications (26)45.01 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The chemical composition and antibacterial activity of Thymus glabrescens Willd. (Lamiaceae) essential oil were examined, as well as the association between it and chloramphenicol. The antibacterial activities of geraniol and thymol, the main constituents of T. glabrescens oil, individually and in combination with chloramphenicol, were also determined. The interactions of the essential oil, geraniol, and thymol with chloramphenicol toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemometric methods. Oxygenated monoterpenes were the most abundant compound class in the oil, with geraniol (22.33%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antibiotic and thymol. A combination of T. glabrescens oil and chloramphenicol produced a strong synergistic interaction (FIC indices in the range 0.21–0.87) and a substantial reduction of the MIC value of chloramphenicol, thus minimizing its adverse side effects. The combinations geraniol-chloramphenicol and thymol-chloramphenicol produced synergistic interaction to a greater extent, compared with essential oil-chloramphenicol association, which may indicate that the activity of the thyme oil could be attributed to the presence of significant concentrations of geraniol and thymol.
    Full-text · Article · Jan 2014 · The Scientific World Journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: The study was aimed at determining the origin and geological evolution of lignites from the Smederevsko Pomoravlje field (Kostolac Basin, Serbia). The possibility of a rational utilization of the coal was also considered. For this purpose, numerous organic geochemical analyses were applied to representative lignite samples. The obtained results showed that the coal from the Smederevsko Pomoravlje field is a typical humic coal. The peat-forming vegetation was dominated by gymnosperm plants. The coal-forming plants belonged to the gymnosperm families Taxodiaceae, Cupressaceae, Phyllo-cladaceae and Pinaceae. Other precursors of organic matter (OM) were microbial biomass ferns and angiosperms. It was established that peatification occurred in a neutral to slightly acidic, fresh water environment Under anoxic to suboxic redox conditions. The maturity of the OM is low, in the phase of intense diagenetic processes. The biomarker compositions and values of the corresponding parameters revealed that the Smederevsko Pomoravlje field, the Drmno field (Kostolac Basin) and the "A" field (Kovin deposit) represent a part of a unique lignite basin. The results of this study suggest possible rational utilization of the Smederevsko Pomoravlje lignites in thermal power plants. This is particularly related to samples from coal seam I. A significant amount of gas could be generated from lignites at higher maturities. Eight samples met the basic assumptions for effective gasification.
    No preview · Article · Jan 2014 · Journal of the Serbian Chemical Society
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The composition and antimicrobial activity of the essential oil of Heracleum sibiricum L. (Apiaceae) was studied. The aerial part of plant was hydro-distilled and chemical composition of the essential oil was analyzed by GC and GC-MS. Forty-six compounds, corresponding to 95.12% of the total oil, were identified. Esters represented the major chemical class (69.55%) while the main constituents were octyl butanoate (36.82%), hexyl butanoate (16.08%), 1-octanol (13.62%) and octyl hexanoate (8.10%). Antibacterial activity of the essential oil and reference antibiotics against nine bacterial strains was tested by the broth microdilution method. The results of the bioassays showed that essential oil had slight antimicrobial activities against all tested microorganisms (MIC and MBC values were in the range of 2431.2 to 9724.8 microg/mL). Reference antibiotics were active in concentrations between 0.5 and 16.0 microg/mL. The results confirm that Gram-positive bacteria were more susceptible to the essential oil of H. sibiricum, in comparison with Gram-negative bacteria.
    Full-text · Article · Sep 2013 · Natural product communications
  • Source
    B. Ilić · D. Miladinović · B. Kocić · V. Ćirić · O. Cvetković

    Full-text · Conference Paper · Aug 2013
  • Source
    B. Ilić · D. Miladinović · B. Kocić · V. Ćirić · O. Cvetković

    Full-text · Conference Paper · Aug 2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The Upper Miocene lignite from the Main coal seam in the D field, Kolubara basin, is a typical humic coal with huminite, liptinite and inertinite concentrations of up to 83.7 vol.%, 17.2 vol.% and 15.5 vol.%, respectively. In the huminite group, textinite and ulminite are the most abundant macerals with variable amounts of densinite and attrinite. Liptodetrinite and sporinite are the most common macerals of the liptinite group, while inertodetrinite is the most abundant maceral of the inertinite group. The mineral matter consists mostly of clay minerals. The main sources of organic matter were gymnosperms (conifers) and microbial biomass, followed by angiosperms. Based on composition of saturated and aromatic diterpenoids it has been established that coal forming plants belonged to the gymnosperm families Taxodiaceae, Podocarpaceae, Cupressaceae, Araucariaceae, Phyllocladaceae and Pinaceae. Peatification occurred in neutral to slightly acidic, fresh water environment Composition and distribution of biomarkers show that diagenetic changes of the organic matter were mainly governed by bacterial activity in a suboxic to oxic environment Based on distribution of aromatic diterpenoids a novel diagenetic pathway for transformation of abietane-type precursors under suboxic to oxic conditions is proposed. Variations in compositions of macerals and biomarkers are in concordance with pronounced seasonality during Pontian, which caused changes in the water level, redox conditions during peatification, and to some extent vegetation differences in the paleo-plant communities.
    Full-text · Article · May 2013 · International Journal of Coal Geology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to research the seasonal changes of antioxidant enzyme activity and total antioxidant capacity in leaves of Astragalus onobrychis L. subsp. chlorocarpus (Griseb.) S. Kozuharov et D.K. Pavlova. Leaves of A. onobrychis were collected during the different stages of growth and analyzed for antioxidant enzyme activity: superoxide dismutase, catalase, guaiacol peroxidase, glutathione peroxidase. Quantities of malonyldialdehyde, superoxide radicals, and hydroxyl radicals were measured as well as the content of soluble proteins. Furthermore, total antioxidant capacity was determined by the inhibition of chemiluminescence activity of blood phagocytes by leaf extracts. Stages of vegetation significantly affected the accumulation of superoxide radicals, but there were no significant differences in hydroxyl radical quantity and lipid peroxidation levels during vegetation. Soluble proteins vary greatly between different stages of growth. Seasonal changes were found to have an effect on enzymatic activities. During the spring season, guaiacol peroxidase showed the highest levels. Catalase and glutathione peroxidase increased their activities in summer, while, during the autumn season, superoxide dismutase showed maximum activity. On the basis of chemiluminescence assay, it can be concluded that leaf extract of A. onobrychis possesses a significant antioxidant capacity thus protecting plants during environmental stress.
    Full-text · Article · Feb 2013 · Central European Journal of Chemistry
  • Source

    Full-text · Chapter · Jan 2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cited By (since 1996):1, Export Date: 18 October 2014
    No preview · Article · Jan 2013 · Central European Journal of Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The antibacterial effects of Thymus vulgaris (Lamiaceae), Lavandula angustifolia (Lamiaceae), and Calamintha nepeta (Lamiaceae) Savi subsp. nepeta var. subisodonda (Borb.) Hayek essential oils on five different bacteria were estimated. Laboratory control strain and clinical isolates from different pathogenic media were researched by broth microdilution method, with an emphasis on a chemical composition-antibacterial activity relationship. The main constituents of thyme oil were thymol (59.95%) and p-cymene (18.34%). Linalool acetate (38.23%) and beta-linalool (35.01%) were main compounds in lavender oil. C. nepeta essential oil was characterized by a high percentage of piperitone oxide (59.07%) and limonene (9.05%). Essential oils have been found to have antimicrobial activity against all tested microorganisms. Classification and comparison of essential oils on the basis of their chemical composition and antibacterial activity were made by utilization of appropriate chemometric methods. The chemical principal component analysis (PCA) and hierachical cluster analysis (HCA) separated essential oils into two groups and two sub-groups. Thyme essential oil forms separate chemical HCA group and exhibits highest antibacterial activity, similar to tetracycline. Essential oils of lavender and C. nepeta in the same chemical HCA group were classified in different groups, within antibacterial PCA and HCA analyses. Lavender oil exhibits higher antibacterial ability in comparison with C. nepeta essential oil, probably based on the concept of synergistic activity of essential oil components.
    Full-text · Article · Mar 2012 · Analytical and Bioanalytical Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of the study was to determine the origin and to reconstruct the geological evolution of lignites from the Drmno field (Kostolac Basin, Serbia). For this purpose, petrological and organic geochemical analyses were used. Coal from the Drmno field is typical humic coal. Peat-forming vegetation dominated by decay of resistant gymnosperm (coniferous) plants, followed by prokaryotic organisms and angiosperms. The coal forming plants belonged to the gymnosperm families Taxodiaceae, Podocarpaceae, Cupressaceae, Araucariaceae, Phyllocladaceae and Pinaceae. Peatification was realised in a neutral to slightly acidic, fresh water environment. Considering that the organic matter of the Drmno lignites was deposited at the same time, in a relatively constant climate, it could be supposed that climate probably had only a small impact on peatification. Therefore, variations in compositions of macerals and biomarkers indicate changes in the water level, due to seasonal drying of the mire, which caused vegetation differences in the palaeoplant communities and changes in the redox conditions (from anoxic to slightly oxic) during peatification. Diagenetic transformations of the organic matter were mainly governed by microbial activity, rather than thermal alteration.
    Full-text · Article · Jan 2012 · Journal of the Serbian Chemical Society
  • [Show abstract] [Hide abstract]
    ABSTRACT: Photocatalytic degradation of synthesized azo pyridone dye (5-(4-sulpho phenylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridone), in aqueous solutions by simulated sunlight in the presence of commercial TiO(2), Aeroxide P25, was studied. The reaction kinetics analysis showed that photodegradation exhibits pseudo first-order kinetics according to Langmuir-Hinshelwood model. The effects of various process parameters on the photocatalytic degradation were investigated. The optimal catalyst content and pH were determined. A decrease in the reaction rate was observed upon the increase of the initial dye concentration. Degradation of the dye was enhanced by hydrogen peroxide, but it was inhibited by ethanol. The influence of temperature was studied, and the energy of activation was determined. According to total organic carbon (TOC) analysis, 54% of TOC remained when 100% of the dye was decolorized. Although the intermediates were not determined in this study, the TOC results clearly indicate their presence during the reaction. In addition, photocatalytic degradation of simulated dyehouse effluents, containing tested azo pyridone dye and associated auxiliary chemicals was investigated.
    No preview · Article · Jan 2011 · Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A petrological and organic geochemical study was performed on coal samples from the East field deposit, Bogovina Basin, Serbia. Fourteen coal samples were collected from different parts of the Main and Upper coal seams from fresh, working faces in the underground subbituminous coal mine. The Lower Miocene (?) coal of the East field is a typical humic coal with huminite, liptinite and inertinite concentrations of up to 81.4 vol.%, 16.1 vol.% and 13.5 vol.%, respectively. Densinite is the most abundant maceral with variable amounts of ulminite and gelinite. Sporinite and liptodetrinite are the most common macerals of the liptinite group. Exsudatinite was detected in the lower part of the Lower coal seam. Inertodetrinite is the most abundant maceral of the inertinite group. The mineral matter consists mostly of clay minerals and carbonates. The mean random huminite reflectance (ulminite B) for the Main coal seam is 0.42 ± 0.04%Rr, and 0.41 ± 0.04%Rr for the Upper coal seam, which are typical for an immature to early mature stage of the organic matter.
    Full-text · Article · Apr 2010 · International Journal of Coal Geology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Soft brown coals of the open coal fields of Kolubara and Kostolac are the main domestic energy sources of Serbia. This paper presents the results of investigations on rapid devolatilization of these two coals it which have covered kinetics of devolatilization (based on total volatile yield), forms of sulphur and petrographic analysis of coal and char. Experiments of devolatilization were performed in inert gas (N(2)) at atmospheric pressure and in batch-type hot-wire screen reactor. The mass-loss values of both coals at selected final reaction temperatures (300-900 degrees C) and retention times (3-28 s) were obtained Anthony and Howard's kinetic model was applied over two temperature ranges (300-500 and 700-900 degrees C). The types of sulphur as monosulphide, sulphate, pyritic, and organic sulphur were determined for chars and original coals. Strong transformation of pyrite was evident even at low temperatures (300 degrees C). Devolatilization of all types of sulphur has started over 600 and at 900 degrees C the content of sulphur in char remained only 66% of total sulphur in original coal. Microscopic investigations were carried out on samples prepared for reflected light measurements. The petrographic analysis included: the ratio of unchanged and changed coal, maceral types, the share of cenosferes, isotropic mixed carbonized grains, mixed grains, small fragments, clay, and pyrite. The change of the structure of devolatilized coal was also observed
    Full-text · Article · Jan 2009 · Thermal Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the molecular composition and biomarker distribution of lacustrine sediments from Val-1 drillhole in the central zone of the western part of the Valjevo-Mionica basin were investigated at depth interval of 0–400 m. Former investigations have shown that the core material can be separated into six depth intervals based on bulk geochemical, mineralogical and sedimentological characteristics. Concerning the quality of organic matter, presence of specific minerals, and high salinity and anoxicity, or alkalinity, three zones are of highest interest, defined at depth intervals of 15–75 m (A), 75–200 m (B) and 360–400 m (F). The first aim of the study was to identify which biomarkers characterize these specific intervals. The second aim, addressing the transitions zones of these intervals, was to extend the changes in the characteristics of the organic substance, to reflect the changes of conditions in the depositional environment as well as to define biomarker parameters which are the most sensitive sedimentological indicators.
    No preview · Article · Sep 2008 · Chemie der Erde - Geochemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A petrological, organic geochemical and geochemical study was performed on coal samples from the Soko Mine, Soko Banja basin, Serbia. Ten coal and two carbonaceous clay samples were collected from fresh, working faces in the underground brown coal mine from different parts of the main coal seam. The Lower Miocene, low-rank coal of the Soko Mine is a typical humic coal with huminite concentrations of up to 76.2 vol.%, liptinite less than 14 vol.% and inertinite less than 11 vol.%. Ulminite is the most abundant maceral with variable amounts of densinite and clay minerals. Sporinite and resinite are the most common macerals of the liptinite group. Inertodetrinite is the most abundant maceral of the inertinite group. The mineral-bituminous groundmass identified in some coal samples, and carbonaceous marly clay, indicate sub-aquatic origin and strong bacterial decomposition. The mean random huminite reflectance (ulminite B) for the main coal seam is 0.40 ± 0.05% Rr, which is typical for an immature to early mature stage of organic matter.The extract yields from the coal of the Soko Banja basin ranges from 9413 to 14,096 ppm, in which alkanes constituted 1.0–20.1%, aromatics 1.3–14.7%, asphaltenes 28.1–76.2% and resins 20.2–43.5%. The saturated hydrocarbon fractions included n-C15 to n-C32, with an odd carbon number that predominate in almost all the samples. The contents of n-C27 and n-C29 alkanes are extremely high in some samples, as a contribution of epicuticular waxes from higher plants. Acyclic isoprenoid hydrocarbons are minor constituents in the aliphatic fraction, and the pristane/phytane (Pr/Ph) ratio varies between 0.56 and 3.13, which implies anaerobic to oxic conditions during sedimentation. The most abundant diterpanes were abietane, dehydroabietane and 16α(H)-phyllocladane. In samples from the upper part of the coal seam, diterpanes are the dominant constituents of the alkane fraction. Polycyclic alkanes of the triterpane type are important constituents of alkane fractions. The occurrence of ββ- and αβ-type hopanes from C27 to C31, but without C28, is typical for the Soko Banja coals.The major and trace elements in the coal were analysed using X-ray fluorescence (XRF), and inductively coupled plasma-mass spectrometry (ICP-MS). In comparison with world lignites, using the geometric mean value, the coal from the Soko Banja Basin has a high content of strontium (306.953 mg/kg). Higher values than the world lignites were obtained for Mo (3.614 mg/kg), Ni (8.119 mg/kg), Se (0.884 mg/kg), U (2.642 mg/kg) and W (0.148 mg/kg). Correlation analysis shows inorganic affinity for almost all the major and trace elements, except for S, which has an organic affinity.
    Full-text · Article · Feb 2008 · International Journal of Coal Geology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Eco-chemical characteristics of the soil from the Velika Morava River valley were examined by analysis of 27 samples of agricultural soil of fluvisol type. The main physico-chemical parameters (pH, carbonate, humus, total nitrogen, available potassium and phosphorus contents), and total and available contents of heavy metals (Pb, Zn, Cu and Cd) were determined. The aim of this research was to have an insight into the current eco-chemical state in the examined agricultural region, by detection of the main substrates of heavy metals, as well as by analysis of their possible origin. In all the examined samples, total Zn, Cu and Cd contents, and in most of the examined samples, total contents of Pb, obtained by sequential extraction, were below maximum allowed concentrations (MAC) for agricultural soils. The increased content of total Pb (104.28-161.03 mg/kg) in some of the examined samples was probably caused by anthropogenic activity. Results of the sequential extraction, as well as the extraction with diethylene triamine pentaacetic acid (DTPA), used for extraction of available metals, indicated the anthropogenic sources of Pb, Cu and Cd, whereas Zn was most often of geochemical, native origin. The obtained results were subject to correlation and factor analysis. Both methods confirmed the correlation between Zn and Cd, leading to the conclusion that a part of Zn was also of anthropogenic origin. Factor analysis brought together total contents of Zn and Cd, and pH-value of the soil, and indicated the possibility of its easy mobilisation at slight changes in soil acidity.
    No preview · Article · Jan 2006 · Fresenius Environmental Bulletin

  • No preview · Conference Paper · Sep 2005
  • D. Đurka · P. Pfendt · B. Jovančićević · O. Cvetković · H. Wehner
    [Show abstract] [Hide abstract]
    ABSTRACT: Free and associated bitumens were isolated by sequential extraction from Vlasina lake peat (SE Serbia) and were investigated in order to differentiate between oil pollution and natural bitumens. Four peat samples were collected at different depths, on a peat island. Gas chromatographic (GC) and gas chromatography/mass spectrometry (GC/MS) analysis revealed the presence of three markedly different bitumen fractions. Here we show that the free bitumens are representing the native peat bitumens. The two associated bitumens are mainly the products of bacterial rework of organic substance, which were then trapped by two differing mechanisms. The bitumens characteristics and association features exclude a contribution of oil pollution.
    No preview · Article · Jul 2005 · Environmental Chemistry Letters
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The factor analysis, used in this work for the interpretation of maturation parameters observed in an exploration study of a group of surface sediments of diverse age originating from different localities in Serbia, resulted in two significant factors. Factor 1 involved parameters related mainly to maturation changes within the aliphatic chains of the organic matter and factor 2 involved parameters based mainly on changes in the terpane and sterane rings. A statistically significant inversely proportional linear dependence between factors 1 and 2 was observed with older, in contrast to younger sediments, suggesting that the reactions of the aliphatic chains in the older sediments did not occur simultaneously with the reactions in the rings and, also, that the older surface sediments examined in this study may be characterized by a degree of thermal maturity corresponding to changes in the biomarker sterane and terpane rings, while the younger sediments by intensive changes in the aliphatic chains.
    Preview · Article · Jan 2004 · Journal of the Serbian Chemical Society