TY  - JOUR
A1  - Fayez, Shaimaa
A1  - Feineis, Doris
A1  - Aké Assi, Laurent
A1  - Seo, Ean-Jeong
A1  - Efferth, Thomas
A1  - Bringmann, Gerhard
T1  - Ancistrobreveines A–D and related dehydrogenated naphthylisoquinoline alkaloids with antiproliferative activities against leukemia cells, from the West African liana Ancistrocladus abbreviatus
JF  - RSC Advances
N2  - A unique series of six biaryl natural products displaying four different coupling types (5,10 , 7,10 , 7,80 , and 5,80) were isolated from the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Although at first sight structurally diverse, these secondary metabolites all have in common that they belong to the rare group of naphthylisoquinoline alkaloids with a fully dehydrogenated isoquinoline portion. Among the African Ancistrocladus species, A. abbreviatus is so far only the second one that was found to produce compounds with such a molecular entity. Here, we report on four new representatives, named ancistrobreveines A–D (12–14, and 6). They were identified along with the two known alkaloids 6-O-methylhamateine (4) and entdioncophylleine A (10). The two latter naphthylisoquinolines had so far only been detected in Ancistrocladus species from Southeast Asia. All of these fully dehydrogenated alkaloids have in common being optically active despite the absence of stereogenic centers, due to the presence of the rotationally hindered biaryl axis as the only element of chirality. Except for ent-dioncophylleine A (10), which lacks an oxygen function at C-6, the ancistrobreveines A–D (12–14, and 6) and 6-O-methylhamateine (4) are 6-oxygenated alkaloids, and are, thus, typical ‘Ancistrocladaceae-type’ compounds. Ancistrobreveine C (14), is the first – and so far only – example of a 7,80-linked fully dehydrogenated naphthylisoquinoline discovered in nature that is configurationally stable at the biaryl axis. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR) and chiroptical (electronic circular dichroism) methods. Ancistrobreveine C (14) and 6-O-methylhamateine (4) exhibited strong antiproliferative activities against drug-sensitive acute lymphoblastic CCRF-CEM leukemia cells and their multidrugresistant subline, CEM/ADR5000.
KW  - chemistry
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201686
VL  - 9
IS  - 28
ER  - 
TY  - JOUR
A1  - Mufusama, Jean-Pierre
A1  - Feineis, Doris
A1  - Mudogo, Virima
A1  - Kaiser, Marcel
A1  - Brun, Reto
A1  - Bringmann, Gerhard
T1  - Antiprotozoal dimeric naphthylisoquinolines, mbandakamines B\(_3\) and B\(_4\), and related 5,8′-coupled monomeric alkaloids, ikelacongolines A–D, from a Congolese Ancistrocladus liana
JF  - RSC Advances
N2  - From the leaves of a botanically and phytochemically as yet unexplored Ancistrocladus liana discovered in the rainforests of the Central region of the Democratic Republic of the Congo in the vicinity of the town of Ikela, six new naphthylisoquinoline alkaloids were isolated, viz., two constitutionally unsymmetric dimers, the mbandakamines B\(_3\) (3) and B\(_4\) (4), and four related 5,8′-linked monomeric alkaloids, named ikelacongolines A–D (5a, 5b, 6, and 7). The dimers 3 and 4 are structurally unusual quateraryls comprising two 5,8′-coupled monomers linked via a sterically strongly constrained 6′,1′′-connection between their naphthalene units. These compounds contain seven elements of chirality, four stereogenic centers and three consecutive chiral axes. They were identified along with two known related compounds, the mbandakamines A (1) and B\(_2\) (2), which had so far only been detected in two Ancistrocladus species indigenous to the Northwestern Congo Basin. In addition, five known monomeric alkaloids, previously found in related Central African Ancistrocladus species, were isolated from the here investigated Congolese liana, three of them belonging to the subclass of 5,8′-coupled naphthylisoquinoline alkaloids, whereas two compounds exhibited a less frequently occurring 7,8′-biaryl linkage. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR), chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. The mbandakamines B\(_3\) (3) and B\(_4\) (4) displayed pronounced activities in vitro against the malaria parasite Plasmodium falciparum and the pathogen of African sleeping sickness, Trypanosoma brucei rhodesiense.
KW  - chemistry
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201141
VL  - 9
IS  - 21
ER  - 
TY  - JOUR
A1  - Wawra, Stephan
A1  - Fesel, Philipp
A1  - Widmer, Heidi
A1  - Timm, Malte
A1  - Seibel, Jürgen
A1  - Leson, Lisa
A1  - Kesseler, Leona
A1  - Nostadt, Robin
A1  - Hilbert, Magdalena
A1  - Langen, Gregor
A1  - Zuccaro, Alga
T1  - The fungal-specific beta-glucan-binding lectin FGB1 alters cell-wall composition and suppresses glucan-triggered immunity in plants
JF  - Nature Communications
N2  - β-glucans are well-known modulators of the immune system in mammals but little is known about β-glucan triggered immunity in planta. Here we show by isothermal titration calorimetry, circular dichroism spectroscopy and nuclear magnetic resonance spectroscopy that the FGB1 gene from the root endophyte Piriformospora indica encodes for a secreted fungal-specific β-glucan-binding lectin with dual function. This lectin has the potential to both alter fungal cell wall composition and properties, and to efficiently suppress β-glucan-triggered immunity in different plant hosts, such as Arabidopsis, barley and Nicotiana benthamiana. Our results hint at the existence of fungal effectors that deregulate innate sensing of β-glucan in plants.
KW  - Effectors in plant pathology
KW  - Fungal host response
KW  - Lectins
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-165945
VL  - 7
ER  - 
TY  - JOUR
A1  - Ronald, Micura
A1  - Höbartner, Claudia
T1  - Fundamental studies of functional nucleic acids: aptamers, riboswitches, ribozymes and DNAzymes
JF  - Chemical Society Reviews
N2  - This review aims at juxtaposing common versus distinct structural and functional strategies that are applied by aptamers, riboswitches, and ribozymes/DNAzymes. Focusing on recently discovered systems, we begin our analysis with small-molecule binding aptamers, with emphasis on in vitro-selected fluorogenic RNA aptamers and their different modes of ligand binding and fluorescence activation. Fundamental insights are much needed to advance RNA imaging probes for detection of exo- and endogenous RNA and for RNA process tracking. Secondly, we discuss the latest gene expression–regulating mRNA riboswitches that respond to the alarmone ppGpp, to PRPP, to NAD+, to adenosine and cytidine diphosphates, and to precursors of thiamine biosynthesis (HMP-PP), and we outline new subclasses of SAM and tetrahydrofolate-binding RNA regulators. Many riboswitches bind protein enzyme cofactors that, in principle, can catalyse a chemical reaction. For RNA, however, only one system (glmS ribozyme) has been identified in Nature thus far that utilizes a small molecule – glucosamine-6-phosphate – to participate directly in reaction catalysis (phosphodiester cleavage). We wonder why that is the case and what is to be done to reveal such likely existing cellular activities that could be more diverse than currently imagined. Thirdly, this brings us to the four latest small nucleolytic ribozymes termed twister, twister-sister, pistol, and hatchet as well as to in vitro selected DNA and RNA enzymes that promote new chemistry, mainly by exploiting their ability for RNA labelling and nucleoside modification recognition. Enormous progress in understanding the strategies of nucleic acids catalysts has been made by providing thorough structural fundaments (e.g. first structure of a DNAzyme, structures of ribozyme transition state mimics) in combination with functional assays and atomic mutagenesis.
KW  - Functional nucleic acids
KW  - RNA Enzymes
KW  - RNA labeling
KW  - nucleoside modification recognition
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212133
ET  - Advance Article
ER  - 
TY  - JOUR
A1  - Pimentel-Elardo, Sheila M.
A1  - Buback, Verena
A1  - Gulder, Tobias A. M.
A1  - Bugni, Tim S.
A1  - Reppart, Jason
A1  - Bringmann, Gerhard
A1  - Ireland, Chris M.
A1  - Schirmeister, Tanja
A1  - Hentschel, Ute
T1  - New Tetromycin Derivatives with Anti-Trypanosomal and Protease Inhibitory Activities
JF  - Marine drugs
N2  - Four new tetromycin derivatives, tetromycins 1-4 and a previously known one, tetromycin B (5) were isolated from Streptomyces axinellae Pol001(T) cultivated from the Mediterranean sponge Axinella polypoides. Structures were assigned using extensive 1D and 2D NMR spectroscopy as well as HRESIMS analysis. The compounds were tested for antiparasitic activities against Leishmania major and Trypanosoma brucei, and for protease inhibition against several cysteine proteases such as falcipain, rhodesain, cathepsin L, cathepsin B, and viral proteases SARS-CoV M(pro), and PL(pro). The compounds showed antiparasitic activities against T. brucei and time-dependent inhibition of cathepsin L-like proteases with K(i) values in the low micromolar range.
KW  - cysteine protease
KW  - drugs
KW  - streptomyces
KW  - discovery
KW  - anti-trypanosomal
KW  - protease inhibition
KW  - Streptomyces axinellae
KW  - marine sponge
KW  - tetromycin
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-141171
VL  - 9
IS  - 10
ER  - 
TY  - JOUR
A1  - Walter, T.
A1  - Collenburg, L.
A1  - Japtok, L.
A1  - Kleuser, B.
A1  - Schneider-Schaulies, S.
A1  - Müller, N.
A1  - Becam, J.
A1  - Schubert-Unkmeir, A.
A1  - Kong, J. N.
A1  - Bieberich, E.
A1  - Seibel, J.
T1  - Incorporation and visualization of azido-functionalized N-oleoyl serinol in Jurkat cells, mouse brain astrocytes, 3T3 fibroblasts and human brain microvascular endothelial cells
JF  - Chemical Communications
N2  - The synthesis and biological evaluation of azido-N-oleoyl serinol is reported. It mimicks biofunctional lipid ceramides and has shown to be capable of click reactions for cell membrane imaging in Jurkat and human brain microvascular endothelial cells.
KW  - Ceramide
KW  - Apoptosis
KW  - Golgi
KW  - N-oleoyl serinol
KW  - Jurkat cells
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191263
VL  - 52
IS  - 55
ER  - 
TY  - JOUR
A1  - Wächtler, Maria
A1  - Kübel, Joachim
A1  - Barthelmes, Kevin
A1  - Winter, Andreas
A1  - Schmiedel, Alexander
A1  - Pascher, Torbjörn
A1  - Lambert, Christoph
A1  - Schubert, Ulrich S.
A1  - Dietzek, Benjamin
T1  - Energy transfer and formation of long-lived \(^3\)MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands
JF  - Physical Chemistry Chemical Physics
N2  - Multimetallic complexes with extended and highly conjugated bis-2,2':6',2''-terpyridyl bridging ligands, which present building blocks for coordination polymers, are investigated with respect to their ability to act as light-harvesting antennae. The investigated species combine Ru(II)- with Os(II)- and Fe(II)-terpyridyl chromophores, the latter acting as energy sinks. Due to the extended conjugated system the ligands are able to prolong the lifetime of the \(^3\)MLCT states compared to unsubstituted terpyridyl species by delocalization and energetic stabilization of the \(^3\)MLCT states. This concept is applied for the first time to Fe(II) terpyridyl species and results in an exceptionally long lifetime of 23 ps for the Fe(II) \(^3\)MLCT state. While partial energy (>80%) transfer is observed between the Ru(II) and Fe(II) centers with a time-constant of 15 ps, excitation energy is transferred completely from the Ru(II) to the Os(II) center within the first 200 fs after excitation.
KW  - polypyridyl complexes
KW  - bis-terpyridyl ligands
KW  - multimetallic complexes
KW  - metal-to-ligand charge transfer (MLCT)
KW  - RU-(II) complexes
KW  - Ru(II)–Fe(II)–Ru(II) complex
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191041
VL  - 18
IS  - 4
ER  - 
TY  - JOUR
A1  - Kar, Haridas
A1  - Gehrig, Dominik W.
A1  - Allampally, Naveen Kumar
A1  - Fernández, Gustavo
A1  - Laquai, Frédéric
A1  - Ghosh, Suhrit
T1  - Cooperative supramolecular polymerization of an amine-substituted naphthalene-diimide and its impact on excited state photophysical properties
JF  - Chemical Science
N2  - A donor-acceptor-donor (D-A-D) type naphthalene-diimide (NDI-H) chromophore exhibits highly cooperative J-aggregation leading to nanotubular self-assembly and gelation in n-decane, as demonstrated by UV/Vis, FT-IR, photoluminescence and microscopy studies. Analysis of temperature-dependent UV/Vis spectra using the nucleation-elongation model and FT-IR data reveals the molecular origin of the cooperative nature of the self-assembly. The supramolecular polymerization is initiated by H-bonding up to a degree of polymerization similar to 20-25, which in a subsequent elongation step promotes J-aggregation in orthogonal direction leading to possibly a sheet-like structure that eventually produces nanotubes. Time-resolved fluorescence and absorption measurements demonstrate that such a tubular assembly enables very effective delocalization of excited states resulting in a remarkably prolonged excited state lifetime.
KW  - nanotube
KW  - supramolecular polymerization
KW  - NDI-H
KW  - UV/Vis spectroscopy
KW  - FT-IR spectroscopy
KW  - transient absorption
KW  - nucleation-elongation model
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191459
VL  - 7
IS  - 2
ER  - 
TY  - JOUR
A1  - Ceyman, Harald
A1  - Rosspeintner, Arnulf
A1  - Schreck, Maximilian H.
A1  - Mützel, Carina
A1  - Stoy, Andreas
A1  - Vauthey, Eric
A1  - Lambert, Christoph
T1  - Cooperative enhancement versus additivity of two-photon-absorption cross sections in linear and branched squaraine superchromophores
JF  - Physical Chemistry Chemical Physics
N2  - The linear and nonlinear optical properties of a series of oligomeric squaraine dyes were investigated by one-photon absorption spectroscopy (1PA) and two-photon absorption (2PA) induced fluorescence spectroscopy. The superchromophores are based on two indolenine squaraine dyes with transoid (SQA) and cisoid configuration (SQB). Using these monomers, linear dimers and trimers as well as star-shaped trimers and hexamers with benzene or triphenylamine cores were synthesised and investigated. The red-shifted and intensified 1PA spectra of all superchromophores could well be explained by exciton coupling theory. In the linear chromophore arrangements we also found superradiance of fluorescence but not in the branched systems. Furthermore, the 2PA showed enhanced cross sections for the linear oligomers but only additivity for the branched systems. This emphasizes that the enhancement of the 2PA cross section in the linear arrangements is probably caused by orbital interactions of higher excited configurations.
KW  - 2-photon absorption
KW  - Vibronic contributions
KW  - One-photon
KW  - Molecules
KW  - Intensity
KW  - Multibranched structures
KW  - Optical properties
KW  - Dyes
KW  - Chromophores
KW  - Design
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188299
VL  - 18
IS  - 24
ER  - 
TY  - JOUR
A1  - Fayez, Shaimaa
A1  - Feineis, Doris
A1  - Mudogo, Virima
A1  - Awale, Suresh
A1  - Bringmann, Gerhard
T1  - Ancistrolikokines E-H and related 5,8\('\)-coupled naphthylisoquinoline alkaloids from the Congolese liana \(Ancistrocladus\) \(likoko\) with antiausterity activities against PANC-1 human pancreatic cancer cells
JF  - RSC Advances
N2  - A striking feature of the metabolite profile of \(Ancistrocladus\) \(likoko\) (Ancistrocladaceae) is the exclusive production of 5,8\('\)-linked naphthylisoquinoline alkaloids varying in their OMe/OH substitution patterns and in the hydrogenation degree in their isoquinoline portions. Here we present nine new compounds of this coupling type isolated from the twigs of this remarkable Central African liana. Three of them, the ancistrolikokines E (9), E\(_2\) (10), and F (11), are the first 5,8\('\)-linked naphthyldihydroisoquinolines found in nature with \(R\)-configuration at C-3. The fourth new metabolite, ancistrolikokine G (12), is so far the only representative of the 5,8\('\)-coupling type that belongs to the very rare group of alkaloids with a fully dehydrogenated isoquinoline portion. Moreover, five new \(N\)-methylated naphthyltetrahydroisoquinolines, named ancistrolikokines A\(_2\) (13), A\(_3\) (14), C\(_2\) (5), H (15), and H\(_2\) (16) are presented, along with six known 5,8\('\)-linked alkaloids, previously identified in related African \(Ancistrocladus\) species, now found for the first time in \(A.\) \(likoko\). The structural elucidation was achieved by spectroscopic analysis (HRESIMS, 1D and 2D NMR) and by chemical (oxidative degradation) and chiroptical (electronic circular dichroism) methods. The new ancistrolikokines showed moderate to good preferential cytotoxic activities towards pancreatic PANC-1 cells in nutrient-deprived medium (NDM), without causing toxicity under normal, nutrient-rich conditions, with ancistrolikokine H\(_2\) (16) being the most potent compound.
KW  - chemistry
KW  - Ancistrocladus likoko
KW  - alkaloids
KW  - bioactive compound
KW  - anti-cancer-agent
KW  - pancreatic cancer
KW  - naphthylisoquinoline alkaloid
KW  - spectroscopic analysis
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172008
VL  - 7
IS  - 85
ER  -