Ekaterina Eguereva

Apralactone A and a New Stereochemical Class of Curvularins from the Marine Fungus Curvularia sp.

Chemical investigations of the cytotoxic extract of the marine-derived fungus Curvularia sp. (strain no. 768), isolated from the red alga Acanthophora spicifera, yielded the novel macrolide apralactone A (1), as well as the antipodes of curvularin macrolides 2-7. Compound 8, a dimeric curvularin was recognised as an artefact. The structures of 1-8 were elucidated by interpretation of their spectroscopic data (1D and 2D NMR, CD, MS, UV and IR). Apralactone A (1) is a 14-membered phenyl acetic acid macrolactone, and the first such compound with a 4-chromanone substructure. Compounds 1, 2, 4, 5 and 6 were found to be cytotoxic towards human tumor cell lines with mean IC50 values in the range of 1.25 to 30.06 µM.

Ten-Membered Lactones from the Marine-Derived Fungus Curvularia sp.

Investigation of the secondary metabolites of the marine-derived fungus Curvularia sp. yielded four new 10-membered lactones (1-4), along with the known modiolide A (5). The structures of 1-4 were characterized on the basis of spectroscopic and MS data and resemble known 10-membered lactones, but feature modified oxidation patterns around their macrocycles.

Hydroxylated Sclerosporin Derivatives from the Marine-derived Fungus Cadophora malorum

The marine-derived fungus Cadophora malorum was isolated from the green alga Enteromorpha sp. Growth on a biomalt medium supplemented with sea salt yielded an extract, from which we have isolated sclerosporin and four new hydroxylated sclerosporin derivatives, namely, 15-hydroxysclerosporin (2), 12-hydroxysclerosporin (3), 11-hydroxysclerosporin (4), and 8-hydroxysclerosporin (5). The compounds were evaluated in various biological activity assays. Compound 5 showed a weak fat-accumulation inhibitory activity against 3T3-L1 murine adipocytes.

Unprecedented Polyketides from a Marine Sponge-Associated Stachylidium sp.

From the marine sponge-derived fungus Stachylidium sp. six novel phthalide-related compounds, cyclomarinone (1), maristachones A-E (2-5), and marilactone (6), were isolated. The structure of compound 1 comprises a hydroxycyclopentenone ring instead of the furanone ring characteristic for phthalides and represents a new carbon arrangement within polyketides. In the epimeric compounds 5a and 5b the phthalide (=isobenzofuranone) nucleus is modified to an isobenzofuran ring with ketal and acetal functionalities. Biosynthetically the structural skeletons of cyclomarinone (1) and maristachones A (2), C (4), D (5a), and E (5b) are most unusual due to the presence of an additional carbon atom when compared to the basic polyketide skeleton. This special biosynthetic feature also holds true for the likewise isolated polyketide marilactone (6).