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Arthrinins A–D: Novel diterpenoids and further constituents from the sponge derived fungus Arthrinium sp.(Bioorganic & Medicinal Chemistry
Volume 19, Issue 15, 1 August 2011, Pages 4644-4651 )


Sherif S. Ebada(a), h, Barbara Schulz(b), Victor Wray(c), Frank Totzke(d), Michael H.G. Kubbutat(d), Werner E.G. Müller(e), Alexandra Hamacher(f), Matthias U. Kassack(f), Wenhan Lin(g) and Peter Proksch(a),

a Institut für Pharmazeutische Biologie und Biotechnologie, Heinrich-Heine-Universität, Geb. 26.23, Universitätsstrasse 1, D-40225 Düsseldorf, Germany

b Institut für Mikrobiologie, Technische Universität Carolo-Wilhelmina zu Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany

c Biophysikalische Analytik Abteilung, Helmholz Zentrum für Infektionsforschung, Inhoffenstrasse 7, D-38124 Braunschweig, Germany

d ProQinase GmbH, Breisacher Strasse 117, D-79106 Freiburg, Germany

e Institute for Physiological Chemistry, University Medical Center of the Johannes-Gutenberg-University Mainz, Duesbergweg 6, D-55128 Mainz, Germany

f Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine Universität, Universitätsstrasse 1, Geb. 26.23, D-40225 Düsseldorf, Germany

g State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing 100083, China

h Department of Pharmacognosy and Phytochemistry, Faculty of Pharmacy, Ain-Shams University, Organization of African Unity 1, 11566 Cairo, Egypt
Received 21 March 2011;
revised 25 May 2011;
accepted 2 June 2011.
Available online 20 June 2011.

Abstract

Bioassay-guided fractionation of a methanolic extract of the fungus Arthrinium sp., isolated from the Mediterranean sponge Geodia cydonium, afforded 10 natural products including five new diterpenoids, arthrinins A–D (1–4) and myrocin D (5). In addition, five known compounds were obtained, which included myrocin A (6), norlichexanthone (7), anomalin A (8), decarboxycitrinone (9) and 2,5-dimethyl-7-hydroxychromone (10). The structures of all isolated compounds were unambiguously elucidated based on extensive 1D and 2D NMR and HR-MS analyzes. The absolute configuration of arthrinins A–D (1–4) was established by the convenient Mosher method performed in NMR tubes and by interpretation of the ROESY spectra. Antiproliferative activity of the isolated compounds was assessed in vitro against four different tumor cell lines, including mouse lymphoma (L5178Y), human chronic myelogenous leukemia (K562), human ovarian cancer (A2780) and cisplatin-resistant ovarian cancer cells (A2780CisR), using the MTT assay. Norlichexanthone (7) and anomalin A (8) exhibited the strongest activities with IC50 values ranging from 0.40 to 74.0 μM depending on the cell line investigated. This was paralleled by the inhibitory activity of both compounds against 16 cancer related protein kinases including aurora-B, PIM1, and VEGF-R2. In vitro IC50 values of 7 and 8 against these three protein kinases ranged from 0.3 to 11.7 μM. Further investigation of the potential antitumoral activity of compounds 5–8 was performed in an in vitro angiogenesis assay against human umbilical vascular endothelial cells (HUVEC) sprouting induced by vascular endothelial growth factor A (VEGF-A). Anomalin A (8), myrocin D (5) and myrocin A (6) inhibited VEGF-A dependent endothelial cell sprouting with IC50 values of 1.8, 2.6 and 3.7 μM, respectively, whereas norlichexanthone (7) was inactive.


Keywords: Diterpenoid; Arthrinium; Cytotoxicity; Protein kinase inhibition; Antiproliferative

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Sourcing Marine Natural Products E. coli delivers marine natural product from genes of symbiotic bacteria

	MAUREEN ROUHI
	HOST-GUEST COOPERATION Patellamide A, originally isolated from the sea squirt Lissoclinum patella (show), is actually made by the symbiotic bacteria that the marine invertebrate harbors. Now, Escherichia coli can make it, too. CARSTEN WOLFF/AUSTRALIAN INSTITUTE OF MARINE SCIENCE The biosynthetic genes for certain bioactive peptides have been isolated from bacteria living symbiotically in sea squirts and expressed in Escherichia coli, according to a new study. The work offers a sustainable way to supply marine natural products for human use. Many marine natural products are potentially therapeutic. The true source of these bioactive compounds, however, has been hotly debated, says William Fenical of Scripps Institution of Oceanography. On the basis of structures, scientists have suspected that bioactive compounds from marine invertebrates are made by the symbiotic bacteria they harbor. Last year, two groups identified bacterial symbiont genes likely to be responsible for polyketides in a marine sponge (Proc. Natl. Acad. Sci. USA 2004, 101, 16222) and for bryostatins in a marine bryozoan (Chem. Biol. 2004, 11, 1543). The researchers did not settle the issue of source because they did not show that the genes lead to the natural products. As Jon Clardy of Harvard Medical School puts it, "Looking at a gene sequence doesn't put compounds in a bottle." Now, for the cytotoxic cyclic peptides called patellamides, Eric W. Schmidt at the University of Utah; Jacques Ravel at the Institute for Genomic Research, Rockville, Md.; and coworkers have taken the next step to pinpoint the source. After identifying the biosynthetic genes from the genome of Prochloron didemni, which is the bacterial symbiont of the sea squirt Lissoclinum patella, they cloned the genes and inserted them in E. coli, which produced the expected compounds (Proc. Natl. Acad. Sci. USA 2005, 102, 7315). The work is the first "to establish that the small molecule is really made by the symbiotic microbe," Clardy says. Major efforts have been undertaken to produce marine natural products synthetically, given that supplies are limited and difficult to sustain, he explains. "Now, we're inching closer to a good supply source by culturing and not by synthesis," he adds. Fenical--as well as David J. Newman of the National Cancer Institute--tells C&EN that scientists in Australia and the U.K. disclosed similar results last November at a meeting of the Society for Industrial Microbiology in San Diego. Team member Marcel Jaspars of the University of Aberdeen, Scotland, says they used shotgun cloning to express the patellamide genes in E. coli, whereas Schmidt and colleagues used a deliberate approach. "Our next step was to be the sequencing of the producing clones, which would have led us to the same conclusions" as in the PNAS paper, Jaspars says. "We have not yet been successful in publishing our work," he adds. Meanwhile, Schmidt's lab is continuing to improve the harvest of patellamides from E. coli to support a slew of experiments Schmidt is eager to do. At the top of his list, he says, is testing the flexibility of the biosynthetic pathway.
	Chemical & Engineering News ISSN 0009-2347 Copyright © 2005

Marine sponges; a potent source of bioactive compounds

Marine animals in general and marine invertebrates in particular are promising organisms for synthesis of novel bioactive compounds. This is an adaptation strategy to thrive in the extreme environmental conditions of the sea and as a defense strategy to escape from predators by the marine invertebrates especially soft bodied animals like sponges (Werner et al., 2004). Focusing on sponges, a conceptual progress occurred with the study of Thakur et al. (2003), who suggested that marine animals and their symbiotic microorganisms (bacteria and fungi) produce an array of bioactive compounds against foreign attackers. Pharmaceutical interest in sponges was aroused in the early 1950’s by the discovery of a number of unknown nucleosides: spongothymidine and spongouridine in the marine sponge Cryptotethia crypta (Bergmann and Feeney, 1950; 1951). These nucleosides were the basis for the synthesis of Ara-C, the first marine derived anticancer agent and the antiviral drug Ara-A (Proksch et al., 2002). Ara-C is currently used in the routine treatment of patients with leukaemia and lymphoma. More than 15.000 marine products have been described up to now (MarinLit, 1999; Faulkner, 2000; 2001; 2002). Sponges are champion producers, concerning the diversity of products that have been found. They are responsible for more than 5300 different products and every year hundreds of new compounds are being discovered (Faulkner 2000; 2001; 2002). Most bioactive compounds from sponges can be classified as antiinflammatory, antitumour, immuno- or neurosurpressive, antiviral, antimalarial, antibiotic or antifouling. The chemical diversity of sponge products is remarkable. In addition to the unusual nucleosides, bioactive terpenes, sterols, cyclic peptides, alkaloids, fatty acids, peroxides, and amino acid derivatives (which are frequently halogenated) have been described from sponges.