The marine fungus Chondrostereum sp. was collected from a soft coral of the species Sarcophyton tortuosum from the South China Sea. Three new compounds, chondrosterins F–H (1, 4 and 5), together with three known compounds, incarnal (2), arthrosporone (3), and (2E)-decene-4,6,8-triyn-1-ol (6), were isolated. Their structures were elucidated primarily based on NMR and MS data. Incarnal (2) exhibited potent cytotoxic activity against various cancer cell lines.
By the method of 1 H NMR prescreening and tracing the diagnostic signals, 6-methylpyridinone derivatives, (8R,9S)-dihydroisoflavipucine (1), (8S,9S)-dihydroisoflavipucine (2), 3-(1-hydroxy-4-methyl-2-oxopentylidene)-6-methylpyridine-2,4(1H,3H)-dione (3), 4-hydroxy-3-(2-hydroxy-4-methylpentanoyl)-6-methylpyridin-2(1H)-one (4), 4-hydroxy-3-[(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)methyl]-6-methylpyridin-2(1H)-one (5) and a known 6-methylpyranone derivative 3,3 0 -methylenebis(4-hydroxy-6-methyl-2H-pyran-2-one) (6) were isolated from the marine fungus Leptosphaerulina sp., which was collected from the starfish Acanthaster planci from the South China Sea. Compounds 2 and 3 are new compounds. Their structures were elucidated on the basis of MS, 1D and 2D NMR, and X-ray single crystal diffraction data. The absolute configurations of compounds 1 and 2 were determined by analysis on the experimental circular-dichroism spectra. ª 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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