Cytotoxic indole alkaloids and polyketides produced by a marine-derived fungus DS720.

Marine-derived microorganisms possess the unique metabolic pathways to produce structurally novel secondary metabolites with potent biological activities. In this study, bioactivity-guided isolation of the marine deep-sea-derived fungus DS720 led to the characterization of four indole alkaloids (compounds -) and four polyketides (compounds -), such as two new indoles, flavonoids A () and B () with a C-6 reversed prenylation, and a new azaphilone, flaviazaphilone A (). Their chemical structures were unambiguously established by an extensive interpretation of spectroscopic data, such as 1D/2D NMR and HRESIMS data. The absolute configurations of the new compound were solved by comparing the experimental and calculated Electronic Circular Dichroism (ECD) spectra. Since sufficient amount of flavonoids A () was obtained, was subjected to a large-scale cytotoxic activity screening against 20 different human tumor cell lines. The results revealed that showed broad-spectrum cytotoxicities against HeLa, 5637, CAL-62, PATU8988T, A-375, and A-673 cell lines, with the inhibition rates of more than 90%. This study indicated that the newly discovered indole alkaloid may possess certain potential for the development of lead compounds in the future.