Natural Products, Stylissadines A and B, Specific Antagonists of the P2X7 Receptor, an Important Inflammatory Target

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Buchanan, Malcolm S
Carroll, Anthony R
Addepalli, Rama
Avery, Vicky M
Hooper, John NA
Quinn, Ronald J
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2007
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Abstract

The distribution of the P2X7 receptor in inflammatory cells suggests that P2X7 antagonists have a significant role to play in the treatment of inflammatory disease. We conducted a natural product high-throughput screening campaign to discover P2X7 receptor antagonists. The Australian marine sponge Stylissa flabellata yielded two new bisimidazo-pyrano-imidazole bromopyrrole ether alkaloids, stylissadines A (IC50 0.7 uM) and B (IC50 1.8 uM), as the specific bioactive constituents. The compounds inhibit BzATP-mediated pore formation in THP-1 cells. Also present in this extract was considerable nonspecific bioactivity in the hemeolysin specificity assay. A new pyrrole-imidazole alkaloid, konbu'acidin B, and the known pyrrole-imidazole alkaloids 4,5-dibromopalau'amine and massadine were also isolated and had nonspecific activity. ROESY and proton coupling constant data indicated that the stereochemistry at C12, C17, and C20 in 4,5-dibromopalau'amine should be revised to 12R, 17S, 20S. By analogy, the relative stereochemistry of palau'amine, 4-bromopalau'amine, styloguanidine, 3-bromostyloguanidine, and 2,3-dibromostyloguanidine should also be revised to 12R, 17S, 20S. Stylissadines A and B are the most potent natural product P2X7 antagonists to be isolated to date and provide a novel class of P2X7 receptor inhibitors. They are also the first examples of tetrameric pyrrole-imidazole alkaloids.

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Journal of Organic Chemistry

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72

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7

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© 2007 American Chemical Society. Self-archiving of the author-manuscript version is not yet supported by this publisher. The contents of this journal can be freely accessed online via the ACS web page after publication. Use hypertext link above to access the ACS website.

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Medicinal and biomolecular chemistry

Organic chemistry

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