Isolation and Bioassay of Linear Veraguamides from a Marine Cyanobacterium (Okeania sp.)

Marine cyanobacteria have gained momentum in recent years as a source of novel bioactive small molecules. This paper describes the structure elucidation and pharmacological evaluation of two new (veraguamide O (1) and veraguamide P (2)) and one known (veraguamide C (3)) analogs isolated from a cyanobacterial collection made in the Las Perlas Archipelago of Panama. We hypothesized that these compounds would be cytotoxic in cancer cell lines. The compounds were screened against HEK-293, estrogen receptor positive (MCF-7), and triple-negative breast cancer (MDA-MB-231) cells as well as against a broad panel of membrane-bound receptors. The planar structures were determined based on NMR and MS data along with a comparison to previously isolated veraguamide analogs. Phylogenetic analysis of the collection suggests it to be an Okeania sp., a similar species to the cyanobacterium reported to produce other veraguamides. Veraguamide O shows no cytotoxicity (greater than 100 μM) against ER-positive cells (MCF-7) with 13 μM IC₅₀ against MDA-MB-231 TNBC cells. Interestingly, these compounds show affinity for the sigma2/TMEM-97 receptor, making them potential leads for the development of non-toxic sigma 2 targeting ligands.