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排序方式: 共有217条查询结果,搜索用时 15 毫秒
101.
Novel Chromone Derivatives from Marine Fungus Aspergillus versicolor Isolated from the Sponge Xestospongia exigua 总被引:2,自引:0,他引:2
Wen Han LIN* Hong Zheng FU Jun LI Peter Proksch National Research Laboratories of Natural Biomimetic Drugs Peking University Beijing Institut fuer Pharmazeutwasche Biologie Heinrich-Heine Universitat Duesseldorf D- 《中国化学快报》2001,(3)
In the continuation of our research for the bioactive secondary metabolites from the sponge-associated fungi, the bioassay guiding fractionation led to the isolation of six new secondary metabolites with unusual skeleton based on chromone ring system from the inoculated fungus Aspergillus versicolor, that had been isolated from fresh samples of marine sponge Xestospongia exigua, collected along coast line of Bali, Indonesia in 1997. The basic skeleton of those compounds possessed an oxohexacy… 相似文献
102.
Omeje EO Osadebe PO Esimone CO Nworu CS Kawamura A Proksch P 《Natural product research》2012,26(19):1775-1781
Column fractionation and purification of an n-hexane fraction led to the isolation of three lupeol-based triterpenoid esters from the leaves of the Eastern Nigeria mistletoe, Loranthus micranthus Linn parasitic on a local kola nut tree, Kola acuminata. These three compounds were adequately characterised using a combination of UV/visible, IR, NMR (13C-NMR and 1H-NMR), DEPT, MS and two-dimensional correlation (H-H COSY, Hetero-nuclear Single Quantum Correlation (HSQC), HMBC, NOE and NOESY) studies as 7β,15α-dihydroxyl-lup-20(29)-ene-3β-esters of palmitic (I), stearic (II) and eicosanoic acids (III). The characterisation of other isolated compounds is ongoing. Remarkably, this is the first report of the existence of fatty acid esters of an unusual 7β,15α-dihydroxylated lupeol in the Eastern Nigeria mistletoe. These isolated compounds might contribute in part to the numerous established bio-activities of the Eastern Nigeria mistletoes. 相似文献
103.
Anja Wehrmann Stefan Puttnins Lars Hartmann Martin Ehrhardt Pierre Lorenz Klaus Zimmer 《Optics & Laser Technology》2012,44(6):1753-1757
Laser patterning of thin-film solar cells is essential to perform external serial and integrated monolithic interconnections for module application and has recently received increasing attention. Current investigations show, however, that the efficiency of thin-film Cu(In,Ga)Se2 (CIGS) modules is reduced due to laser scribing also with ultrashort laser pulses. Hence, to investigate the reasons of the laser-induced material modifications, thin-film CIGS solar cells were laser-scribed with femto- and picosecond laser pulses using different scribing procedures and laser processing parameters. Besides standard electrical current voltage (I–V) measurements, additional electrical and optical analysis were performed such as laser beam-induced current (LBIC), dark lock-in thermography (DLIT), and electroluminescence (EL) measurements to characterize and localize electrical losses due to material removal/modifications at the scribes that effecting the electrical solar cell properties. Both localized as well as distributed shunts were found at laser scribe edges whereas the laser spot intensity distribution affecting the shunt formation. Already laser irradiation below the ablation threshold of the TCO film causes material modification inside the thin film solar cell stack resulting in shunt formation as a result of materials melting near the TCO/CIGS interface that probably induces the damage of the pn-junction. 相似文献
104.
A chemical investigation of Jaspis sp., the marine sponge collected from the South China Sea led to the isolation of six new isomalabaricane-type compounds, jaspolides A-F (1-6). The structures of those compounds were elucidated by extensive spectroscopic methods. The structure-types of 1 to 6 could be classified into triterpenes (1, 2), sesterterpene (6), diterpenes (3, 4), and nortriterpene (5). The biogenetic transformation of the isolated compounds was also speculated. 相似文献
105.
K. Zimmer R. B?hme M. Ehrhardt B. Rauschenbach 《Applied Physics A: Materials Science & Processing》2010,101(2):405-410
In consequence of high interest in micro- and nanomachining of transparent materials by laser irradiation, studies on the
mechanism of laser-induced backside wet etching (LIBWE) are presented. To reveal the role of the surface modification due
to LIBWE the backside ablation (BSA) of LIBWE-modified fused silica (mFS) surfaces at 248 nm was investigated. The threshold
fluence and the etch rate of BSA are similar to that of LIBWE and amount ∼250 mJ/cm2 and 30 nm for 1 J/cm2, respectively. The sample transmission after backside ablation of mFS increases and proves the decreasing thickness of the
absorbing layer. Time-resolved reflection studies at LIBWE and BSA of mFS show similar patterns in the backside reflection
that can be assigned an ablation process as the comparison to thin polymer films demonstrates. By fitting the BSA data to
an exponential decay absorption model a modification depth and a surface absorption of about 38 nm and α
S
∼1.3×107 m−1 were calculated, respectively. In conclusion of the results a new model for LIBWE is proposed. 相似文献
106.
Lena Hammerschmidt Abdessamad Debbab Tu Duong Ngoc Victor Wray Catalina Perèz Hemphil WenHan Lin Heike Broetz-Oesterhelt Matthias U. Kassack Peter Proksch Amal H. Aly 《Tetrahedron letters》2014
Five new polyketide derivatives, 6′-hydroxypestalotiopsone C (1), acropyrone (2), bicytosporone D (3), waol acid (4), and pestalotiopene C (5), together with seven known metabolites (6–12), were obtained from extracts of the endophytic fungus Acremonium strictum, isolated from the mangrove tree Rhizophora apiculata. The structures of the isolated compounds were elucidated on the basis of comprehensive NMR and MS analysis. Compounds 6, 7, and 9 showed moderate cytotoxic activity against human cisplatin-sensitive (IC50 values 27.1, 76.2, and 8.3 μM, respectively) and resistant A2780 cell lines (IC50 values 12.6, 30.1, and 19.0 μM, respectively), whereas only 9 exhibited antibacterial activity against Staphylococcus aureus (MIC value 14.3 μM). 相似文献
107.
Nineteen new cembranoids with unusual capnosane skeleton named trocheliophols A–S (1–19) together with four known analogues were isolated from the Chinese soft coral Sarcophyton trocheliophorum. Their structures were determined on the basis of extensive spectroscopic (IR, MS, 1D and 2D NMR) analysis, in addition to the modified Mosher's method, CD and X-ray diffraction for the configuration assignments. The inhibitory effects of the isolated compounds against inflammation-related NF-κB and bacterial pathogens were evaluated. Compounds 8, 9 and 19 exhibited potent inhibitory effects against phytopathogens and human disease-related Gram positive and negative bacteria, while the preliminary structure–activity relationship is discussed. 相似文献
108.
Festus Basden Chiedu Okoye Abdessamad Debbab Victor Wray Charles Okechukwu Esimone Patience Ogoamaka Osadebe Peter Proksch 《Tetrahedron letters》2014
Maytenus senegalensis Lam. (Celastraceae) leaves are traditionally used in West Africa for the management of cancer and other disorders associated with inflammation. In this study, bioactivity-guided fractionation of the methanol leaf extract of Maytenus senegalensis led to the isolation of 11 compounds, including the new phenyldilactone, maysedilactone (1). All isolated compounds were tested for cytotoxicity against mouse lymphoma cell line (L5178Y). Only (−) epigallocathechin showed high cytotoxicity and completely inhibited cell growth at the investigated dose of 10 μg/mL. This result supports the claimed efficacy of Maytenus senegalensis leaf extract in ethnomedicinal treatment of cancer. 相似文献
109.
Antonius R.B. Ola Abdessamad Debbab Amal H. Aly Attila Mandi Ilka Zerfass Alexandra Hamacher Matthias U. Kassack Heike Brötz-Oesterhelt Tibor Kurtan Peter Proksch 《Tetrahedron letters》2014
Neosartorin (1) was isolated from the endophytic fungus Aspergillus fumigatiaffinis. The absolute configuration of 1, including both axial and central chirality elements, was established as (aR,5S,10R,5′S,6′S,10′R) for the first time on the basis of its electronic circular dichroism (ECD) spectra aided with TDDFT–ECD calculations. Neosartorin (1) exhibited substantial antibacterial activity against a broad spectrum of Gram-positive bacterial species including staphylococci, streptococci, enterococci, and Bacillus subtilis with minimal inhibitory concentrations in the range of 4–32 μg/mL. When the toxicity of 1 against eukaryotic cells was measured using a panel of different cancer cell lines such as HELA and BALB/3T3, the average IC50 values exceeded 32 μg/mL. 相似文献
110.
Thermal modifications due to interfacial compound formation in magnetron sputtered Cr-C multilayers have been investigated in the temperature range between 450° C and 580° C and the formation of interfacial carbides has been discussed on the basis of thermodynamic and kinetic considerations. Grain boundary diffusion accompanied by grain growth proportional to the reacted layer thickness has been assumed to account for the observed t1/3 time dependence of the growth rate. The compound layer growth has been thermally activated with an activation energy of QG=0.85 eV. 相似文献