Two new diterpene pyrones, asperginols
A (1) and B
(2), and four known analogues (3–6) were isolated from the endophytic fungus Aspergillus sp. HAB10R12. The structures and absolute configurations of these
compounds were elucidated based on the analysis of their NMR, MS,
and X-ray diffraction data. The revision of the absolute configurations
at C-10, C-11, and C-14 of the known diterpene pyrones (3–6) and the determination of the configuration
at the polyene side chain for compounds (4–6) were made using chemical methods and vibrational circular
dichroism analysis. This group of diterpene pyrone compounds showed
unique structural features including a 7/6/6 tricyclic diterpene moiety
with an unusual trans–syn–trans stereochemical
arrangement. Compound 6 showed moderate activity against
the HT-29 colon cancer cell line.
A new tetramer oligostilbenoid possessing tetrahydrofuran ring, malaysianol C (1), was isolated from the acetone extract of the stem bark of Dryobalanops lanceolata, together with four known oligostilbenoids nepalensinol E (2), ϵ-viniferin (3), laevifonol (4), and ampelopsin F (5). The structures of isolated compounds were elucidated on the basis of spectral evidence. The antibacterial activity of the isolated compounds was evaluated using resazurin microtitre-plate assay, whereas the cytotoxic activity was tested using MTT assay. The plausible biogenetic routes of the isolated compounds are also discussed.
Svalbardines A and B (1 and 2) and annularin
K (3) were isolated from cultures of Poaceicola sp. E1PB, an endophyte isolated from the petals of Papaver
dahlianum from Svalbard, Norway. Svalbardine A (1) is a pyrano[3,2-c]chromen-4-one, a new analogue
of citromycetin. Svalbardine B (2) displays an unprecedented
carbon skeleton based on a 5′-benzyl-spiro[chroman-3,7′-isochromene]-4,8′-dione core. Annularin
K (3) is a hydroxylated derivative of annularin D. The
structure of these new polyketides, along with those of known compounds 4–6, was established by spectrometric
analysis, including extensive ESI-CID-MS
n
processing in the case of svalbardine B (2).
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