Aulosirazoles B and C from the Cyanobacterium sp. UIC 10771: Analogues of an Isothiazolonaphthoquinone Scaffold that Activate Nuclear Transcription Factor FOXO3a in Ovarian Cancer Cells.

The known solid-tumor-selective cytotoxin aulosirazole () was identified from bioactive extracts from the culture medium of the cyanobacterium sp. UIC 10771. Here, we demonstrate that induces the nuclear accumulation of FOXO3a in OVCAR3 using both Western blot analysis and immunofluorescence confocal microscopy. We also report the discovery of two additional analogues, aulosirazoles B () and C (). Structures for compounds and were determined using HR-ESI-LC-MS/MS and 1D and 2D NMR experiments. Aulosirazoles B () and C () represent the first natural analogues of the FOXO-activating compound aulosirazole () and are the second and third isothiazole-containing metabolites reported from this phylum.