| 1. |
- El-Seedi, Hesham R., et al.
(författare)
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Recent insights into the biosynthesis and biological activities of natural xanthones
- 2010
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Ingår i: Current Medicinal Chemistry. - : Bentham Science Publishers Ltd.. - 0929-8673 .- 1875-533X. ; 17:9, s. 854-901
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Forskningsöversikt (refereegranskat)abstract
- This review focuses on recent advances in our understanding of the complex biosynthetic pathways and diverse biological activities of naturally occurring xanthones. The biosynthesis section covers studies published from 1989 to 2008 on xanthone production in plants and fungi, while the bioactivity review presents tabulated activities of more than 250 xanthones described in studies published from 2001 to 2008, together with structural information and indications of their wide-ranging potential uses as pharmacological tools. A large number of relevant papers have been published on these subjects (128 cited here), illustrating the diversity of the xanthones and their possible uses.
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| 2. |
- Felth, Jenny, 1979-, et al.
(författare)
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Gambogic acid is cytotoxic to cancer cells through inhibition of the ubiquitin-proteasome system
- 2013
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Ingår i: Investigational new drugs. - : Springer Science and Business Media LLC. - 0167-6997 .- 1573-0646. ; 31:3, s. 587-598
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Gambogic acid (GA), displays cytotoxicity towards a wide variety of tumor cells and has been shown to affect many important cell-signaling pathways. In the present work, we investigated the mechanism of action of GA by analysis of drug-induced changes in gene expression profiles and identified GA and the derivative dihydro GA as possible inhibitors of the ubiquitin-proteasome system (UPS). Both GA and dihydro GA inhibited proteasome function in cells resulting in the accumulation of polyubiquitin complexes. In vitro experiments showed that both GA and dihydro GA inhibited 20S chymotrypsin activity and the inhibitory effects of GA and dihydro GA on proteasome function corresponded with apoptosis induction and cell death. In conclusion, our results show that GA and dihydro GA exert their cytotoxic activity through inhibition of the UPS, specifically by acting as inhibitors of the chymotrypsin activity of the 20S proteasome.
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| 3. |
- Johnson, Ann-Louise, et al.
(författare)
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Synthesis of barettin
- 2004
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020 .- 1464-5416. ; 60:4, s. 961-965
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Tidskriftsartikel (refereegranskat)abstract
- The indole alkaloid barettin (with bromine in 6-position), isolated from the marine sponge Geodia Barretti, has been synthesised via a Horner-Wadsworth-Emmons type reaction from 6-bromoindole-3-carboxaldehyde to introduce the dehydro-functionality. Subsequent deprotection and cyclisation afforded the natural product in Z-conformation.
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| 4. |
- Wang, Conan, et al.
(författare)
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Combined X-ray and NMR analysis of the stability of the cyclotide cystine knot fold that underpins its insecticidal activity and potential use as a drug scaffold
- 2009
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 284:16, s. 10672-10683
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Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are a family of plant defense proteins that are highly resistant to adverse chemical, thermal, and enzymatic treatment. Here, we present the first crystal structure of a cyclotide, varv F, from the European field pansy, Viola arvensis, determined at a resolution of 1.8 angstrom. The solution state NMR structure was also determined and, combined with measurements of biophysical parameters for several cyclotides, provided an insight into the structural features that account for the remarkable stability of the cyclotide family. The x-ray data confirm the cystine knot topology and the circular backbone, and delineate a conserved network of hydrogen bonds that contribute to the stability of the cyclotide fold. The structural role of a highly conserved Glu residue that has been shown to regulate cyclotide function was also determined, verifying its involvement in a stabilizing hydrogen bond network. We also demonstrate that varv F binds to dodecylphosphocholine micelles, defining the binding orientation and showing that its structure remains unchanged upon binding, further demonstrating that the cyclotide fold is rigid. This study provides a biological insight into the mechanism by which cyclotides maintain their native activity in the unfavorable environment of predator insect guts. It also provides a structural basis for explaining how a cluster of residues important for bioactivity may be involved in self-association interactions in membranes. As well as being important for their bioactivity, the structural rigidity of cyclotides makes them very suitable as a stable template for peptide-based drug design.
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| 5. |
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| 6. |
- Ahmed, A. Ahmed, et al.
(författare)
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Eudesmane derivatives from Laggera crispata and Pluchea carolonesis
- 1998
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Ingår i: Phytochemistry. - : Elsevier. - 0031-9422 .- 1873-3700. ; 49:8, s. 2421-2424
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of the aerial parts of Laggera crispata and Pluchea carolonesis afforded in addition to several known compounds, three new eudesmane derivatives, 3β,4α-dihydroxy-7-epi-eudesm-11(13)-ene, 3α-(2′,3′-dihydroxy-2′-methylbutanoyl)-4,11-dihydroxy-6,7-dehydroeudesman-8-one and 3α-(3′-chloro-2′-hydroxy-2′-methylbutanoyl)cuauhtemone. The structures were elucidated by spectroscopic methods
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| 7. |
- Sjögren, M., et al.
(författare)
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Antifouling activity of the sponge metabolite agelasine D and synthesised analogs on Balanus improvisus
- 2008
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Ingår i: Biofouling. - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 24:4, s. 251-258
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Tidskriftsartikel (refereegranskat)abstract
- This study reports a screening study for antifouling (AF) activity of the natural compound agelasine D isolated from marine sponges of the genus Agelas and 20 synthesised analogs of agelasines and agelasimines. Agelasine D, together with two of the analogs, ie AV1003A and AKB695, displayed a strong inhibitory effect on settlement of Balanus improvisus cypris larvae. Agelasine D had an EC50 value of 0.11 mu M while the two analogs AV1033A and AKB695 had EC50 values of 0.23 and 0.3 mu M, respectively. None of these three compounds affected larval mortality as was the case with several of the analogs tested. Moreover, the effect of AV1033A and AKB695 was reversible. When cyprids after 24 h exposure to the compounds were transferred to fresh seawater, the settlement frequency compared with the controls was completely recovered. The properties of the agelasine D analogs AV1003A and AKB695 make them highly attractive candidates as AF agents in future marine coatings.
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| 8. |
- Sjögren, Martin, et al.
(författare)
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Two Brominated Cyclic Dipeptides Released by the Coldwater Marine Sponge Geodia barretti Act in Synergy As Chemical Defense
- 2011
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Ingår i: Journal of natural products (Print). - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 74:3, s. 449-454
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Tidskriftsartikel (refereegranskat)abstract
- The current work shows that two structurally similar cyclodipeptides, barettin (1) and 8,9-dihydrobarettin (2), produced by the coldwater marine sponge Geodia barretti Bowerbank act in synergy to deter larvae of surface settlers and may also be involved in defense against grazers. Previously, 1 and 2 were demonstrated to bind specifically to serotonergic 5-HT receptors. It may be suggested that chemical defense in G. barretti involves a synergistic action where one of the molecular targets is a 5-HT receptor. A mixture of 1 and 2 lowered the EC50 of larval settlement as compared to the calculated theoretical additive effect of the two compounds. Moreover, an in situ sampling at 120 m depth using a remotely operated vehicle revealed that the sponge releases these two compounds to the ambient water. Thus, it is suggested that the synergistic action of 1 and 2 may benefit the sponge by reducing the expenditure of continuous production and release of its chemical defense substances. Furthermore, a synergistic action between structurally closely related compounds produced by the same bioenzymatic machinery ought to be the most energy effective for the organism and, thus, is more common than synergy between structurally indistinct compounds.
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| 9. |
- Sjögren, M., et al.
(författare)
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Antifouling activity of synthesized peptide analogs of the sponge metabolite barettin
- 2006
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 27:9, s. 2058-2064
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Tidskriftsartikel (refereegranskat)abstract
- Barettin (cyclo [(6-bromo-8-en-tryptophan) arginine]), a diketopiperazine isolated from the marine sponge Geodia barretti, is a potent inhibitor of barnacle larvae settlement with an EC50-value of 0.9 mu M. In the present study, 14 analogs of barettin and its structural congener dipodazine were synthezised and tested for their ability to inhibit larval settlement. Two of the analogs have an intact barettin skeleton. The remaining analogs have a dipodazine skeleton (a diketopiperazine where arginine is replaced with glycine). Six of the tested synthetic analogs displayed significant settlement inhibition with the most potent inhibitor being benzo[g]dipodazine, which displayed even stronger activity than barettin (EC50-value 0.034 mu M). The effect of benzo[g]dipodazine was also shown to be readily reversible, when cyprids were transferred to filtered seawater (FSW). (c) 2006 Elsevier Inc. All rights reserved.
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| 10. |
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