TY - JOUR A1 - Fayez, Shaimaa A1 - Bruhn, Torsten A1 - Feineis, Doris A1 - Assi, Laurent Aké A1 - Kushwaha, Prem Prakash A1 - Kumar, Shashank A1 - Bringmann, Gerhard T1 - Naphthylisoindolinone alkaloids: the first ring-contracted naphthylisoquinolines, from the tropical liana Ancistrocladus abbreviatus, with cytotoxic activity JF - RSC Advances N2 - The West African liana Ancistrocladus abbreviatus is a rich source of structurally most diverse naphthylisoquinoline alkaloids. From its roots, a series of four novel representatives, named ancistrobrevolines A–D (14–17) have now been isolated, displaying an unprecedented heterocyclic ring system, where the usual isoquinoline entity is replaced by a ring-contracted isoindolinone part. Their constitutions were elucidated by 1D and 2D NMR and HR-ESI-MS. The absolute configurations at the chiral axis and at the stereogenic center were assigned by using experimental and computational electronic circular dichroism (ECD) investigations and a ruthenium-mediated oxidative degradation, respectively. For the biosynthetic origin of the isoindolinones from ‘normal’ naphthyltetrahydroisoquinolines, a hypothetic pathway is presented. It involves oxidative decarboxylation steps leading to a ring contraction by a benzilic acid rearrangement. Ancistrobrevolines A (14) and B (15) were found to display moderate cytotoxic effects (up to 72%) against MCF-7 breast and A549 lung cancer cells and to reduce the formation of spheroids (mammospheres) in the breast cancer cell line. KW - Naphthylisoindolinone alkaloids Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300766 VL - 12 IS - 45 ER - TY - JOUR A1 - Tshitenge Tshitenge, Dieudonné A1 - Bruhn, Torsten A1 - Feineis, Doris A1 - Mudogo, Virima A1 - Kaiser, Marcel A1 - Brun, Reto A1 - Bringmann, Gerhard T1 - An unusually broad series of seven cyclombandakamines, bridged dimeric naphthylisoquinoline alkaloids from the Congolese liana Ancistrocladus ealaensis JF - Scientific Reports N2 - A series of seven unusual dimeric naphthylisoquinoline alkaloids was isolated from the leaves of the tropical liana Ancistrocladus ealaensis J. Léonard, named cyclombandakamine A (1), 1-epi-cyclombandakamine A (2), and cyclombandakamines A3–7 (3–7). These alkaloids have a chemically thrilling structural array consisting of a twisted dihydrofuran-cyclohexenone-isochromene system. The 1′″-epimer of 4, cyclombandakamine A1 (8), had previously been discovered in an unidentified Ancistrocladus species related to A. ealaensis. Both lianas produce the potential parent precursor, mbandakamine A (9), but only A. ealaensis synthesizes the corresponding cyclized form, along with a broad series of slightly modified analogs. The challenging isolation required, besides multi-dimensional chromatography, the use of a pentafluorophenyl stationary phase. Featuring up to six stereocenters and two types of chiral axes, their structures were elucidated by means of 1D and 2D NMR, HRESIMS, in combination with oxidative chemical degradation experiments as well as chiroptical (electronic circular dichroism spectroscopy) and quantum chemical calculations. Compared to the ‘open-chain’ parent compound 9, these dimers displayed rather moderate antiplasmodial activities. KW - Screening KW - Solution-state NMR KW - Stereochemistry KW - Structure elucidation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200759 VL - 9 ER - TY - JOUR A1 - Kunz, Anna Lena A1 - Labes, Antje A1 - Wiese, Jutta A1 - Bruhn, Torsten A1 - Bringmann, Gerhard A1 - Imhoff, Johannes F. T1 - Nature's Lab for Derivatization: New and Revised Structures of a Variety of Streptophenazines Produced by a Sponge-Derived Streptomyces Strain JF - Marine Drugs N2 - Eight streptophenazines (A-H) have been identified so far as products of Streptomyces strain HB202, which was isolated from the sponge Halichondria panicea from the Baltic Sea. The variation of bioactivities based on small structural changes initiated further studies on new derivatives. Three new streptophenazines (I-K) were identified after fermentation in the present study. In addition, revised molecular structures of streptophenazines C, D, F and H are proposed. Streptophenazines G and K exhibited moderate antibacterial activity against the facultative pathogenic bacterium Staphylococcus epidermidis and against Bacillus subtilis. All tested compounds (streptophenazines G, I-K) also showed moderate activities against PDE 4B. KW - marine natural product KW - phenazine KW - Baltic Sea KW - streptomyces KW - halichondria panicea KW - obstructive pulmonary disease KW - phosphodiesterase-4 inhibitor KW - absolute configuration KW - biosynthesis KW - rofumilast Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-116816 SN - 1660-3397 VL - 12 IS - 4 ER - TY - JOUR A1 - Jansen, Nils A1 - Ohlendorf, Birgit A1 - Erhard, Arlette A1 - Bruhn, Torsten A1 - Bringmann, Gerhard A1 - Imhoff, Johannes F. T1 - Helicusin E, Isochromophilone X and Isochromophilone XI: New Chloroazaphilones Produced by the Fungus Bartalinia robillardoides Strain LF550 JF - Marine Drugs N2 - Microbial studies of the Mediterranean sponge Tethya aurantium led to the isolation of the fungus Bartalinia robillardoides strain LF550. The strain produced a number of secondary metabolites belonging to the chloroazaphilones. This is the first report on the isolation of chloroazaphilones of a fungal strain belonging to the genus Bartalinia. Besides some known compounds (helicusin A (1) and deacetylsclerotiorin (2)), three new chloroazaphilones (helicusin E (3); isochromophilone X (4) and isochromophilone XI (5)) and one new pentaketide (bartanolide (6)) were isolated. The structure elucidations were based on spectroscopic analyses. All isolated compounds revealed different biological activity spectra against a test panel of four bacteria: three fungi; two tumor cell lines and two enzymes. KW - tethya aurantium KW - marine natural product KW - azaphilone KW - pentaketide KW - bartalinia robillardoides Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129649 VL - 11 IS - 3 ER -