Nikola D. Nikolić

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.

Physicochemical conditions of sedimentation of the Fish Clay from Stevns Klint, Denmark, and its detrital nature: Vanadium and other supportive evidence

Cretaceous-Tertiary (K/T) boundary samples of the Fish Clay in Denmark from three sites (Stevns Klint, Nye Klov and Dania) have been analyzed mineralogically and chemically. All samples contain major amounts of biogenic calcite and smectite. In some samples, minor amounts of authigenic pyrite and siderite (Stevns Klint), and lepidocrocite (Dania) are also present. To obtain an indication of the chemical nature of the V present in the Danish boundaries, the samples were analysed for V and vanadyl (VO2+) at various stages of selective leaching. The results obtained indicate that the bulk of V is associated with the smectite fractions (≥47% of total V); all VO2+ resides in the smectite portions. From the chemistry of VO2+, pyrite and carbonates, it is deduced that the oxidation potential and pH of the interstitial seawater of the Stevns Klint boundary was approximately 0.0 to −0.2 V and 6 to 7, respectively, during the accumulation of the lower black basal part, but rose during the accumulation of the upper grey part. The geochemical data do support the hypothesis that the Danish boundary smectite represents weathered clay (along with some asteroid and local material) that was redeposited to the Danish boundary sites after the K/T event. Substantial proportions of the VO2+ contents of the Nye Klov and Dania smectite were probably already contained in the detrital clay arriving at the site of boundary sedimentation, but at the Stevns Klint site they have been significantly augmented by uptake from the interfacial and interstitial seawaters through the humic substances involvement. Abundances and major mineralogical residences have been determined for trace metals: Cr, Ni, Co and Ga; and minor Fe. Much of these elements is located in the boundary smectite structure as the corresponding ionic forms (CrOH2+, Ni2+, Co2+, Ga3+ and Fe3+) and is strictly detrital in character, i.e., having been transported to the Danish boundary sites already contained in smectite. All these metals in the Danish boundary smectite are well above normal abundances in clays.

Copper and copper(II) porphyrins of the Cretaceous–Tertiary boundary at Stevns Klint (Denmark)

High levels of copper(II) (Cu 2a ) were found with the major part (s 90%) of the total Cu located in the smectite (Cu: 175 ppm) and kerogen (Cu: up to 1000 ppm) of the basal black marl of the Cretaceous^Tertiary (KT) boundary informal type sedimentary rock: the Fish Clay at Stevns Klint, Denmark. Anomalous abundance (4000 ppm) of the kerogen Cu 2a -porphyrins in this marl was detected by electron spin resonance. A model is proposed in which the enormous acid rains (caused by the KT asteroid impact) washed out the humics (already enriched with Cu 2a /Cu 2a porphyrins) of the top horizon of the nearby oxic soil into the Fish Clay Basin during the KT event. fl 2000 Elsevier Science B.V. All rights reserved.

VOLATILE CONSTITUENTS OF Euphrasia stricta

The genus Euphrasia is fairly large with 450 species distributed in both the hemispheres in Europe, Asia, Northern parts of America, mountains of Indonesia to New Zealand, and South America [1]. The Serbian flora recognizes eight species of Euphrasia genus [2]. Euphrasia stricta J. P. Wolff ex J. F. Lehm. (eyebright) has been a part of the traditional folk medicine for centuries and is used for the treatment of various eye problems such as cataracts, conjunctivitis, and red, inflamed, irritated, and sore eyes [3–5]. The literature data on its constituents and their action is limited. The principal compounds in the aerial part are iridoids, phenolic acids, and phenylpropane, and flavonoid glycosides [6–8]. To the best of our knowledge, there is no report found in the literature on the chemical composition of Euphrasia stricta volatile constituents. Aerial parts of Euphrasia stricta were collected during the flowering period, in August 2011, from natural populations of Bojana s Waters, Suva Planina Mountain, Serbia. A voucher specimen, with the accession number 16517, is deposited at the Herbarium of the Department of Botany, Faculty of Biology, University of Belgrade – Herbarium Code BEOU. Oil was obtained from air-dried aerial parts of the plant in 0.02% (w/w) yield by hydrodistillation for 4 h using a Clevenger-type apparatus. The oil analyses were performed simultaneously by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) systems. The GC analysis of the oil was carried out on an HP-5890 II gas chromatograph equipped with a split-splitless injector on an HP-5MS capillary column (30 m 0.25 mm, 0.25 m film thickness) with helium as the carrier gas (1 mL/min) and flame ionization detector (FID). Operating conditions: injector temperature 250 C and interface temperature 280 C, temperature program from 50 C (3 min) to 250 C at a rate of 3 C/min. GC/MS analyses were performed on an Agilent Technologies apparatus, Model GS 6890N, at 70 eV coupled with a mass selective detector MSD 5975C under the same gas-chromatograph conditions. The identification of compounds was based on a comparison of Kovats retention indexes using AMDIS software (ver. 2.64) in combination with a chemometric multivariate resolution method and selective ion analysis (SIA) [9]. The identity of the compounds was confirmed by comparing their data with those from the literature [10], and their mass spectra with the Wiley 275 and NIST/NBS libraries. Relative retention indexes (RRI) were obtained by co-injection a C9–C28 standard mixture of aliphatic hydrocarbons. The results of GC and GC/MS analyses of the investigated oil are summarized in Table 1. Forty-seven compounds were identified, representing 84.0% of the total oil. Fatty acids and their derivatives were found in large quantities. Palmitic acid was detected as the major component, constituting 20.3% of the oil. Other significant compounds were -palmitolactone (11.4%), ethyl linolate (7.6%), 9,12,15-octadecatrien-1-ol, (Z,Z,Z) (6.1%) and phytol (5.2%), while other constituents were in less than 5%.

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.