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71.
A short synthesis of alkyl 2-(bromomethyl)aziridine-2-carboxylates and alkyl 3-bromoazetidine-3-carboxylates was developed involving amination, bromination, and base-induced cyclization of alkyl 2-(bromomethyl)acrylates. These new small ring azaheterocyclic α- and β-amino acid derivatives are promising synthons as demonstrated by their transformation to 2-(aminomethyl)aziridine-2-carboxylates and 3-aminoazetidine-3-carboxylates. 相似文献
72.
Asta Judzentiene Jurga Budiene Irena Nedveckyte Rasa Garjonyte 《Molecules (Basel, Switzerland)》2022,27(4)
Helichrysum arenarium (L.) Moench (sandy everlasting) is the only species from genus Helichrysum Mill that grows spontaneously in Lithuania. The chemical composition of the essential oils (EOs) from inflorescences and leaves of H. arenarium wild plants was analysed by GC-MS. Palmitic (≤23.8%), myristic (≤14.9%) and lauric (6.1%) acids, n-nonanal (10.4%), and trans-β-caryophyllene (≤6.5%) were the major constituents in the EOs. For comparison, the main components in EO from flowers (commercial herb material) of H. italicum were γ-curcumene (21.5%), β-selinene (13.6%), α-selinene (8.1%), β-eudesmol (8.3%), and α-pinene (6.5%). Composition of H. arenarium methanolic extracts was investigated by HPLC-DAD-TOF. The main compounds were the following: luteolin-7-O-glucoside, naringenin and its glucoside, apigenin, chlorogenic acid, arenol, and arzanol. Antioxidant activity of EOs and extracts was tested by DPPH● and ABTS●+ assays. Sandy everlasting extracts exhibited significantly higher radical scavenging activities (for leaves 11.18 to 19.13 and for inflorescences 1.96 to 6.13 mmol/L TROLOX equivalent) compared to those of all tested EOs (0.25 to 0.46 mmol/L TROLOX equivalent). Antioxidant activity, assayed electrochemically by cyclic and square wave voltammetry correlated with total polyphenolic content in extracts and radical scavenging properties of EOs and extracts. The toxic activity of EOs of both Helichrysum species was evaluated using a brine shrimp (Artemia salina) bioassay. H. italicum inflorescence EO was found to be toxic (LC50 = 15.99 µg/mL) as well as that of H. arenarium (LC50 ≤ 23.42 µg/mL) oils. 相似文献
73.
Judzentiene A Budiene J Butkiene R Kupcinskiene E Laffont-Schwob I Masotti V 《Natural product communications》2010,5(12):1981-1984
The chemical composition of the essential oils of aerial parts of Artemisia campestris ssp. campestris, collected from ten different locations in Lithuania is detailed in this paper. The major component in all the oils was caryophyllene oxide (8.5-38.8%), whereas compounds with the caryophyllane skeleton ranged from 10.2 to 44.5%. Other representative constituents were germacrene D (< or = 15.0%), humulene epoxide II (< or = 8.1%), beta-ylangene (< or = 7.7%), spathulenol (< or = 6.8%), beta-elemene (< or = 6.8%), beta-caryophyllene (< or = 6.2%), junenol (< or = 6.1%) and alpha- or beta-pinene (< or = 5.5%). Eighty-seven compounds were identified, comprising 73.6-92.3% of the oils. The chemical composition was highly variable depending on the sample location. Toxicity of A. campestris oils was determined using the brine shrimp (Artemia sp.) assay. LC50 values ranging to 20 microg/mL were obtained for three of the oils after 24 hours of exposure. Data of this test revealed that A. campestris ssp. campestris essential oils with dominant caryophyllene oxide are notably toxic. 相似文献
74.
Jens Petter Wold Annette Veberg Dahl Frank Lundby Asgeir Nikolai Nilsen Asta Juzeniene Johan Moan 《Photochemistry and photobiology》2009,85(3):669-676
The effect of headspace oxygen concentration and color of light on photo-oxidation and degradation of photosensitizers in butter was studied. Butter samples were stored under 0%, 0.4%, 0.8%, 1.6%, 3.0%, 5.0%, 21% oxygen, and exposed to violet, green or red light. Storage time was 36 h. Degree of photo-oxidation was measured by a trained sensory panel. Photobleaching of six different photosensitizers was estimated based on front face fluorescence excitation and emission landscapes and spectral curve resolution (parallel factor analysis). The higher oxygen concentration, the more sensory degraded were the samples. Violet light resulted in slightly higher degrees of photo-oxidation than green and red light for low oxygen concentrations. Bleaching rate and course as function of O2 concentration differed between the photosensitizers. It is suggested that the rate of photobleaching is a balance between type I and type II photoreactions. 相似文献
75.
C. Dall’Asta A. Faccini G. Galaverna R. Corradini A. Dossena R. Marchelli 《Journal of inclusion phenomena and macrocyclic chemistry》2009,64(3-4):331-340
The complexation of the oestrogenic mycotoxin zearalenone (ZEN) and its metabolites α- and β-zearalenol (ZOLs) with native β-cyclodextrins (β-CD) and modified hydroxypropyl-β-CD and dimethyl-β-CD was studied by fluorescence spectroscopy, nuclear magnetic resonance spectroscopy and electrospray-mass spectrometry. The formation of the inclusion complex was confirmed by NMR studies of zearalenone:β-CD solution. NMR, ESI-MS and fluorescence data are in agreement with the formation of a 1:1 complex between zearalenone and β-CD, characterized by the deep insertion of the phenolic moiety inside the cavity of the CD from its secondary side. The complexes formed between the guests and native β-CD are characterized by high stability constants (>104), as measured by fluorescence titrations. 相似文献
76.
Milišiūnaitė Vaida Kadlecová Alena Žukauskaitė Asta Doležal Karel Strnad Miroslav Voller Jiří Arbačiauskienė Eglė Holzer Wolfgang Šačkus Algirdas 《Molecular diversity》2020,24(4):1025-1042
Molecular Diversity - A series of benzopyrano[2,3-c]pyrazol-4(2H)-one derivatives were synthesized from readily available 1-phenyl- and 1-methyl-1H-pyrazol-3-ols by sequentially employing... 相似文献
77.
Joanna Rymarczyk Elzbieta Czerwosz Asta Richter 《Central European Journal of Physics》2011,9(2):300-306
Atomic force microscopy (AFM) topographical studies and results of nanoindentation experiment for several palladium-carbon
films (Pd-C film) deposited on various substrates and with varying palladium content are presented. Pd-C films were prepared
by a physical vapor decomposition (PVD) process and next were modified by a chemical vapor decomposition (CVD) method to obtain
carbonaceous porous structure with dispersed palladium nanograins and a variation in roughness. 相似文献
78.
79.
We present a method to compute accurately the weak anisotropy of the solid-liquid interfacial free energy, a parameter which influences dendritic evolution in materials with atomically rough interfaces. The method is based on monitoring interfacial fluctuations during molecular dynamics simulation and extracting the interfacial stiffness which is an order of magnitude more anisotropic than the interfacial free energy. We present results for pure Ni with interatomic potentials derived from the embedded atom method. 相似文献
80.
Oliver Warschkow Mark Asta Kenneth R. Poeppelmeier Laurence D. Marks 《Surface science》2004,573(3):446-456
We have recently reported structure solutions for the (2 × 1) and c(4 × 2) reconstructions of SrTiO3(0 0 1) based on high-resolution electron microscopy, direct methods analysis of diffraction data and density functional theory. Both reconstructions were found to be TiO2-rich and feature a single overlayer of TiO2 stoichiometry on top of a bulk-like TiO2 layer. Qualitatively, the two reconstruction geometries differ in the cation sub-lattice of the overlayer only, where Ti atoms occupy half of the fivefold cation sites. In the present work we use density functional theory to generate a number of variations of this structural motif in search of patterns of stability. We find a reliable predictor for the reconstruction energy in the ability of oxygen atoms to relax vertically out of the overlayer plane to minimize non-bonded oxygen-oxygen repulsions. Out-of-plane relaxation of oxygen atoms in turn is modulated by the number and relative position of coordinating Ti atoms, which yields simple empirical rules as to how cations are distributed in low energy reconstructions. 相似文献