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Cytoskyrins and Cytosporones Produced by Cytospora sp. CR200: Taxonomy, Fermentation and Biological Activities

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Author(s): Maya P. Singh | Jeffrey E. Janso | Sean F. Brady

Journal: Marine Drugs
ISSN 1660-3397

Volume: 5;
Issue: 3;
Start page: 71;
Date: 2007;
Original page

Keywords: Cytospora sp. CR200 | cytoskyrins | cytosporones | antimicrobial | cytotoxic

ABSTRACT
In screening endophytic fungi from Costa Rica for bioactivity, fungal culture CR200, isolated from a buttonwood tree, was found to contain compounds that initiate DNA damage in a test strain of E. coli (Biochemical Induction Assay, BIA) and inhibit growth of Gram-positive bacteria, including antibiotic-resistant strains. Two new bisanthraquinones (cytoskyrins A and B) and five new related octaketides (cytosporones A-E) were isolated from fermentation broths of this fungus. Cytoskyrin A exhibited potent in-vitro antibacterial (MICs against Gram-positive bacteria, 0.03 - 0.25 μg/mL) and DNA-damaging activities (10 ng/spot), whereas cytoskyrin B was inactive in these assays. Among the cytosporones, only D and E exhibited Gram-positive activity, but they were inactive in the BIA. Mechanistically, cytoskyrin A specifically inhibited DNA synthesis in E. coli imp at its MIC; however, it also moderately inhibited protein synthesis at 2x its MIC. Cytoskyrin A exhibited poor cytotoxicity against tumor cell lines (IC50 > 5 μg/mL) compared to known antitumor agents. The nuclear ribosomal internal transcribed spacer region of CR200 was found to share highest similarity (94-96%) with Cytospora spp. Micro- and macroscopic morphological observations of the conidia and conidiomata, respectively, also suggested this fungus to be a Cytospora sp.
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