Phenanthrenes from Juncus atratus with antiproliferative activity

The present study has focused on the isolation and structure determination of phenanthrenes from Juncus atratus Krock. Nine compounds, among them five phenanthrenes, have been isolated from the methanol extract of the plant. Two compounds [juncatrins A (1) and B (2)] are new natural products, three phenanthrenes [juncuenin B (3), effusol (4), and dehydroeffusol (5)], the flavones apigenin (7) and luteolin (8), the diterpene phytol and 13(R)-hydroxy-octadeca-(9Z,11E,15Z)-trien-oic acid (9) were isolated for the first time from the plant. Juncatrin A (1) is substitued with an acetyl group, while in case of juncatrin B (2), an unprecedented acetylene group is connected to the phenanthrene skeleton. The isolated phenanthrenes were evaluated for their antiproliferative activity against HeLa, SiHa and MDA-MB-231 human tumor cell lines. Four phenanthrenes (2, 3, 4 and 5) were more effective [IC₅₀s 3.48?μM (2), 2.91 (3), 3.68 (4), and 7.75?μM (5)] than cisplatin (IC₅₀ 12.43?μM) on HeLa cells.     

Identification of Iridoids,Flavonoids and Triterpenes from the Methanolic Extract of Melampyrum bihariense A. Kern. and the Antioxidant Activity of the Extract

Melampyrum bihariense A. Kern. (Scrophulariaceae), a plant species used in traditional medicine for the treatment of rheumatic disorders and skin infections, was investigated with regard to its antioxidant activity and identification of its bioactive chemical constituents. The crude methanolic extract of the aerial parts of M. bihariense was examined by the spectrophotometric DPPH (1,1-diphenyl-2-picrylhydrazyl) and ferric reducing antioxidant power methods. The free radical scavenging capacity (SC₅₀) of the extract was found by the DPPH method to be 27.10 mg mL⁻¹, and the ferric reducing ability equivalent to ascorbic acid at 50 mg mL⁻¹ was 0.709 μg mL⁻¹. The chemical composition of this highly effective in the methanolic extract was analysed, and the main compounds were isolated through solvent–solvent partition, and multiple chromatographic separations, including column chromatography, vacuum liquid chromatography, centrifugal planar chromatography and preparative thin-layer chromatography. The structures were established by one- and two-dimensional NMR and liquid chromatography-mass spectrometry. The iridoids aucubin (1), 8-epi-loganin (2) and mussaenoside (3), the flavones apigenin and luteolin and the triterpene acids ursolic acid and oleanolic acid were identified; components 2, 3, ursolic acid and oleanolic acid for the first time in this species. The present study reveals that M. bihariense exerts antioxidant activity, and the iridoids, flavonoids and triterpene acids may be the main bioactive constituents of its methanolic extract.

     

Selective growth of SWNTs on partially reduced monometallic cobalt catalyst

SiO(2) supported cobalt (Co) catalyst could be partially reduced and anchored by unreduced Co ions during a carbon monoxide (CO) chemical vapor deposition (CVD) process. This resulted in the formation of sub-nanometre metallic Co clusters catalyzing the growth of single-walled carbon nanotubes (SWNTs) with a narrow diameter distribution.     

Diboraperylene Diborinic Acid Self-Assembly on Ag(111)—Kagome Flat Band Localized States Imaged by Scanning Tunneling Microscopy and Spectroscopy

Replacement of sp²-hybridized carbon in polycyclic aromatic hydrocarbons (PAHs) by boron affords electron-deficient π-scaffolds due to the vacant p_z-orbital of three-coordinate boron with the potential for pronounced electronic interactions with electron-rich metal surfaces. Using a diboraperylene diborinic acid derivative as precursor and a controlled on-surface non-covalent synthesis approach, we report on a self-assembled chiral supramolecular kagome network on an Ag(111) surface stabilized by intermolecular hydrogen-bonding interactions at low temperature. Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal a flat band at ca. 0.33 eV above the Fermi level which is localized at the molecule center, in good agreement with tight-binding model calculations of flat bands characteristic for kagome lattices.     

Chemistry and Pharmacology of Cyperaceae Stilbenoids: A Review

Cyperaceae is a cosmopolitan plant family with approx. 5000 species distributed worldwide. Several members of this family are used in traditional medicines for the treatment of different diseases. In the last few decades, constituents with great chemical diversity were isolated from sedges, and a wide range of biological activities were detected either for crude extracts or for pure compounds. Among the isolated compounds, phenolic derivatives are the most important, especially stilbenoids, and flavonoids. To date, more than 60 stilbenoids were isolated from 28 Cyperaceae species. Pharmacological investigation of Cyperaceae stilbenoids revealed that several compounds possess promising activities; mainly antiproliferative, antibacterial, antioxidant and anthelmintic effects. Isolation, synthesis and pharmacological investigation of stilbenes are increasing constantly. As Cyperaceae species are very good sources of a wide variety of stilbenes, and several of them occur in large amount worldwide, they are worthy for phytochemical and pharmacological investigations. Moreover, stilbenes are important from chemotaxonomical point of view, and they play a key role in plant defense mechanisms as well. This review summarizes the stilbenoids isolated from sedges, and their biological activities.     

Der chemische Transport von Cu,Ag, Au,Ru, Rh,Pd, Os,Ir, Pt unter Mitwirkung von Gaskomplexen. Al2Cl6, Fe2Cl6 oder Al2J6 als Komplexbildner

The Chemical Transport of Cu, Ag, Au, Ru, Rh, Pd, Os, Ir, Pt in the Presence of Al₂Cl₆, Fe₂Cl₆ or Al₂I₆, Causing Complex Formation Chemical transport experiments show, that the title elements (with exception of Os) in the presence of halide forming agents (HCl, Cl₂ or I₂ resp.) and of complex forming agents (Al₂Cl₆, Fe₂Cl₆ or Al₂I₆ resp.) give gaseous complex compounds with a remarkable stability. This leads to novel possibilities for the chemical transport of the elements and their compounds. The effect of complex formation can be predicted on the basis of qualitative thermodynamic considerations. The corrosion of the wall of the quartz ampoule at temperatures above 600°C by Al₂Cl₆/AlCl₃ is avoidable by the usage of Fe₂Cl₆/FeCl₃ instead of Al₂Cl₆/AlCl₃. Experiments in the system Pd/I₂, Al₂I₆ lead to the formation of crystals of Pd₂Al.     

Differences in loudness of positive and negative Schroeder-phase tone complexes as a function of the fundamental frequency

Tone complexes with positive (m+) and negative (m-) Schroeder phase show large differences in masking efficiency. This study investigated whether the different phase characteristics also affect loudness. Loudness matches between m+ and m- complexes were measured as a function of (1) the fundamental frequency (f0) for different frequency bands in normal-hearing and hearing-impaired subjects, and (2) intensity level in normal-hearing subjects. In normal-hearing subjects, the level of the m+ stimulus was up to 10 dB higher than that of the corresponding m- stimulus at the point of equal loudness. The largest differences in loudness were found for levels between 20 and 60 dB SL. In hearing-impaired listeners, the difference was reduced, indicating the relevance of active cochlear mechanisms. Loudness matches of m+ and m- stimuli to a common noise reference (experiment 3) showed differences as a function of f0 that were in line with direct comparisons from experiment 1 and indicated additionally that the effect is mainly due to the specific internal processing of m+. The findings are roughly consistent with studies pertaining to masking efficiency and can probably not be explained by current loudness models, supporting the need for incorporating more realistic cochlea simulations in future loudness models.     

All-fiber-coupled laser-induced breakdown spectroscopy sensor for hazardous materials analysis

An all-fiber-coupled laser-induced breakdown spectroscopy (LIBS) sensor device is developed. A passively Q-switched Cr⁴⁺Nd³⁺:YAG microchip laser is amplified within an Yb fiber amplifier, thus generating high power laser pulses (pulse energy E_p = 0.8 mJ, wavelength λ = 1064 nm, repetition rate f_rep. = 5 kHz, pulse duration t_p = 1.2 ns). A passive (LMA) optical fiber is spliced to the active fiber of an Yb fiber amplifier for direct guiding of high power laser pulses to the sensor tip. In front of the sensor a plasma is generated on the surface to be analyzed. The plasma emission is collected by a set of optical fibers also integrated into the sensor tip. The spectrally resolved LIBS spectra are processed by application of principal component analysis (PCA) and analyzed together with the time-resolved spectra with neural networks. Such procedure allows accurate analysis of samples by LIBS even for materials with similar atomic composition. The system has been tested successfully during field measurements at the German Armed Forces test facility at Oberjettenberg.

The LIBS sensor is not restricted to anti-personnel mine detection but has also the potential to be suitable for analysis of bulk explosives and surface contaminations with explosives, e.g. for the detection of improvised explosive devices (IEDs).