Fusaresters A-E, new γ-pyrone-containing polyketides from fungus Fusarium sp. Hungcl and structure revision of fusariumin D.

Marine-derived fungi have been regarded as an under-explored and promising reservoir of structurally novel and bioactive natural products. In this study, five new γ-pyrone-containing polyketides, fusaresters A-E (1-5), were isolated and identified from the culture extracts of a marine-derived fungus Fusarium sp. Hungcl. The structures of compounds 1-5 were elucidated on the basis of their HRESIMS and NMR spectroscopic data as well as 13C NMR calculation and electronic circular dichroism (ECD) analyses. Remarkably, the structure of fusariumin D was revised to (9S*,11S*)-3. All these isolates were tested for the cytotoxicity against seven human cancer cell lines, including SW480, HL-60, A549, MCF-7, HepG2, HeLa and SMMC-7721, and the inhibitory activity against protein tyrosine phosphatase 1B (PTP1B). The results revealed that only compound 2 showed a weak inhibition rate of 56% at 40 μM.