Olga G. Cvetković

Investigation of the chemical composition–antibacterial activity relationship of essential oils by chemometric methods

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 β-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.

Influence of process parameters on the photodegradation of synthesized azo pyridone dye in TiO2 water suspension under simulated sunlight

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 TiO2, 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.

An In Vitro Synergistic Interaction of Combinations of Thymus glabrescens Essential Oil and Its Main Constituents with Chloramphenicol

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.

Simultaneous production of pullulan and biosorption of metals by Aureobasidium pullulans strain CH-1 on peat hydrolysate.

It was demonstrated that during the growth of Aureobasidium pullulans strain CH-1 on the acid hydrolysate of peat from the Vlasina Lake, the content of metals (Cu, Fe, Zn, Mn, Pb, Cd, Ni and Cr) decreased due to biosorption. The reduction in the metal content was found to be in the range (%): 38.2-62.2, 67.7-97.3, 0.02-62.05, 0.05-23.97, 0.16-4.24, 3.45-51.72, 1.18-35.82, 0.86-44.44, for Cu, Fe, Zn, Mn, Pb, Cd, Ni and Cr, respectively. During this process, the metals were accumulated in the biomass, while pullulan, an extracellular polysaccharide produced by Aureobasidium pullulans strain CH-1, was found not to bind the above-mentioned metals.

Direct hydroliquefaction of a low rank soft brown coal

Abstract The behaviour of the soft brown coal from the Kostolac Mine (Serbia, Yugoslavia) was investigated during hydroliquefaction carried out in a batch reactor by direct catalytic hydrogenation of the pulverized coal (−160 μm) dispersed in tetralin. The effects of temperature (ranging from 365 to 440°C), pressure (13.5 to 15.0 MPa) and residence time (1 to 8 h) on the yield of individual liquefaction products as well as the petrographic composition of the coal residues were closely followed by separation and analysis of the products. These consisted of liquid products soluble in n -heptane (light oils), n -heptane insoluble products (asphaltenes), the solid coal residue and gaseous products. A good reactivity of this soft brown coal was observed. The yield of liquid products varied from 23 to 64 wt.% (based on dry ash-free coal). A total coal conversion of 80 to 86% was achieved. Petrographic composition and optical properties of the solid coal residues were analyzed microscopically in order to establish the character and intensity of the coal changes. The solid residues were found to consist of 12 various grain categories. The low proportions of unreacted or partly reacted coal grains confirmed the good reactivity of the Kostolac soft brown coal in the applied liquefaction process.

Antioxidative responses to seasonal changes and chemiluminescence assay of Astragalus onobrychis leaves extract

AbstractThe 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.

Investigation of pretertiary and tertiary surface sediments from Serbia: Organic geochemical interpretation

Samples of surface sediments originating from different localities in Serbia which contained more than 0.5 % organic matter were investigated in this paper. According to age, these samples were classified into two groups sediments of pretertiary age and sediments of tertiary age. Bulk and specific organic geochemical parameters were determined for their methylene chloride-methanol extracts, aimed at controling the relationship between the age of the sediment and the maturity of its organic substance. In this sense a general direct proportionality was observed. However, a better linear dependence of the bulk parameters was observed in the case of younger, tertiary sediments. That is to say, with samples of pretertiary age the organic matter maturity was approaching a definite limiting value contributing to an inferior linear dependence of their bulk maturation parameters. Nevertheless, the dependence was found to be preserved with specific maturation parameters (e.g., CPI; Fit/n-C18), the changes of which are generally more intensive at higher maturity degrees.