No abstract

Bioassay-guided fractionation of the active n-BuOH extract of the sea cucumber Holothuria fuscocinerea resulted in the isolation of three new triterpene glycosides, fuscocinerosides A (1), B (2), and C (3), along with two known glycosides, pervicoside C (4) and holothurin A (5), as active compounds causing morphological abnormality of Pyricularia oryzae mycelia. Compounds 1-5 possess the same tetrasaccharide moiety, 3-O-methyl-beta-D-glucopyranosyl-(1-->3)-beta-D- glucopyranosyl-(1-->4)-beta-D-quinovopyranosyl-(1-->2)-4-O-sodiumsulfato-beta-D-xylopyranosyl, linked to C-3 of holostane triterpene aglycones that differ in their side chains and 17-substituents. Their structures were elucidated by extensive spectral studies as well as chemical evidence. All the glycosides showed in vitro cytotoxicity against two human tumor cell lines.

Two new sulfated triterpene glycosides, philinopside E (1) and F (2), have been isolated from the sea cucumber Pentacta quadrangularis. Their structures have been established by extensive spectral analysis (NMR and MS) and chemical evidence. Glycoside 1 showed significant cytotoxicity (Ed(50) 0.75-3.50 microg mL(-1)) against ten tumor cell lines.

Cytospolides A-E (1-5), five new nonanolides with an unprecedented 15-carbon skeleton with the unique chemical feature of a C-2 methyl group, were isolated from the endophytic fungus Cytospora sp. The structures were elucidated by spectroscopic analysis, chemical interconversion, and single-crystal XRD. The solution and solid state conformers were compared by experimental methods (X-ray, NMR) and solvent and gas phase DFT calculations. The absolute configurations were assigned by time dependent (TD)-DFT calculations of CD spectra, including solution and solid state CD/

By activity-guided fractionation, two new sterols, 3beta,28xi-dihydroxy-24-ethylcholesta-5,23Z-dien (1) and 2a-oxa-2-oxo-5alpha-hydroxy-3,4-dinor-24-ethylcholesta-24(28)-ene (2), together with five known steroids, fucosterol (3), 24-ethylcholesta-4,24(28)-dien-3,6-dione (4), 24xi-hydroperoxy-24-vinylcholesterol (5), 24-ketocholesterol (6), 24R,28R- and 24S, 28S-epoxy-24-ethylcholesterol (7), were isolated from the brown alga Sargassum carpophyllum as active compounds causing morphological abnormality of Pyricularia oryzae mycelia. Compounds 1, 3, 4, 5 and 7 also exhibited cytotoxic activity against various cancer cell lines. The IC50 values for 1 and 5 against HL-60 were 7.8 and 8.5 microg/ml, 3 and 4 against P-388 were 0.7 and 0.8 microg/ml, whereas 7 against MCF-7, HCT-8, 1A9, HOS and PC-3 were 4.0, 8.8, 10.0, 10.0 and 7.2 microg/ml, respectively.

Cytospolides F-Q (6-17) and decytospolides A and B (18 and 19), 14 unusual nonanolide derivatives, were isolated from Cytospora sp., an endophytic fungus from Ilex canariensis. The structures were elucidated by means of detailed spectroscopic analysis, chemical interconversion, and X-ray single crystal diffraction. The solution- and solid-state conformers were compared by the combination of experimental methods (X-ray, NMR) supported by DFT calculations of the conformers. Absolute configurations were assigned using the modified Mosher's method and solution- and solid-state TDDFT ECD calculations. In an in vitro cytotoxicity assay toward the tumor cell lines of A549, HCT116, QGY, A375, and U973, the γ-lactone 17 demonstrated a potent growth inhibitory activity toward the cell line A-549, while nonanolide 16 with (2S) configuration showed the strongest activity against cell lines A-549, QGY, and U973. A cell cycle analysis indicated that compound 16 can significantly mediate G1 arrest in A549 tumor cells, confirming the important role of the C-2 methyl in the growth inhibition toward the tumor line. The discovery of an array of new nonanolides demonstrates the productivity of the fungus, and it is an example of chemical diversity, extending the nonanolide family by derivatives formed by ring cleavage, oxidation, esterification, and Michael addition.

Six new (3Z,5E)-11,20-epoxybriara-3,5-dien-7,18-olide diterpenoids, gemmacolides N–S (1–6), were isolated together with four known analogues, juncenolide D, and juncins R, S and U (7–10), from the South China Sea gorgonian Dichotella gemmacea. The structures of the new compounds were elucidated by the detailed analysis of spectroscopic data in combination with the comparison with reported data. The absolute configuration of 1 was determined by a TDDFT calculation of its solution ECD spectrum, affording the determination of absolute configuration of other analogues by simply comparing their ECD spectra with that of 1. The cytotoxic and antimicrobial activities of these compounds were evaluated. In preliminary in vitro bioassays, compounds 4, 5, 6, 8 and 9 showed cytotoxicity against A549 and MG63, while compounds 1, 2, 4, 7–10 showed antimicrobial activity against the fungus Septoria tritici and the bacterium Escherichia coli.

No abstract